J. Med. Ent.

20 February 1976

Vol. 12, n o . 6: 683-691

DENSITY AND DIVERSITY OF IMMATURE TABANIDAE (DIPTERA) IN RELATION TO HABITAT TYPE IN MENDOCINO COUNTY, CALIFORNIA . 1

B y R o b e r t S. L a n e

a

2

2

2

2

T a b a n i d l a r v a e a r e p r e d o m i n a n t l y i n h a b i t a n t s of w e t l a n d s . T h e y o c c u r i n s u c h sites as soil o r vegetation in seepage areas a n d within a n d along t h e m a r g i n s of c r e e k s , l a k e s , fresh a n d s a l t w a t e r m a r s h e s , p o n d s a n d r i v e r s . S o m e species b r e e d i n terrestrial h a b i t a t s or in tree cavities a n d d e c a y i n g logs. T e r r e s t r i a l h a b i t a t s y i e l d i n g t a b a n i d i m m a ­ t u r e s i n c l u d e g a r d e n soil ( B r i m l e y 1 9 1 1 ) , w o o d l a n d soil ( S c h w a r d t 1 9 3 6 ) , s a n d d e p o s i t s i n h a b i t e d b y t h e l a r v a e of a species of M y r m e l e o n t i d a e ( E n g l i s h 1 9 5 5 ) , d r y - w a s h gullies ( S c h ö m b e r g 1 9 5 2 ) , a n d a n a n t nest (Philip 1973). 'Part of a thesis submitted in partial satisfaction of the require­ ments for the Ph.D. degree from the University of California, Berkeley, Calif. "Research supported by NIAID Traineeship A.I. 00218, Department of Entomological Sciences, University of California, Berkeley. 'Present address: California State Department of Health, Vector Control Section, 2151 Berkeley Way, Berkeley, Calif. 94704, U.S.A.

3

M a n y works containing information on the biology of t a b a n i d i m m a t u r e s h a v e p r e s e n t e d q u a l i t a t i v e , r a t h e r t h a n quantitative, d a t a in relation to habitat. T h e N o r t h A m e r i c a n studies presenting some density d a t a on t a b a n i d i m m a t u r e s have usually dealt with 1 species w i t h i n 1 h a b i t a t t y p e (Bailey 1948, R o t h & L i n d q u i s t 1948, K n u d s e n & R e e s 1968) o r w i t h s e v e r a l species w i t h i n 1 o r 2 h a b i t a t t y p e s ( T a s h i r o & S c h w a r d t 1949, 1 9 5 3 , W a l l & J a m n b a c k 1957, J a m n b a c k & W a l l 1959, R o c k e l & H a n s e n s 1970, F r e e m a n & H a n s e n s 1972, Ellis & H a y s 1 9 7 3 ) . W i l s o n (1969) a n d T h o m p s o n ( 1 9 7 0 , 1971) c o m ­ p a r e d c o l l e c t i o n s of t a b a n i d i m m a t u r e s t a k e n f r o m 3 or 4 major h a b i t a t types. L a n e (1974) s t u d i e d t h e b i o l o g y a n d t a x o n o m y of i m m a t u r e T a b a n i d a e from southeastern M e n d o c i n o County, California, between 1971 a n d 1973. Several potential larval t a b a n i d habitats were i n t e n s i v e l y s a m p l e d t o o b t a i n i m m a t u r e s for r e a r i n g a n d association w i t h the adults, a n d to d e t e r m i n e i n w h i c h h a b i t a t s t h e l a r v a e of different species w e r e found. T h i s report s u m m a r i z e s t h e t y p e s of h a b i t a t s investigated a n d compares t h e m with respect to the d e n s i t y a n d d i v e r s i t y of t h e i r t a b a n i d i n h a b i t a n t s . MATERIALS A N D METHODS

The study area. University

of

Sampling was performed on the

California

Hopland

Field

Station

( H . F . S . ) a n d a l o n g t h e b a n k s of t h e R u s s i a n R i v e r (see b e l o w ) w i t h i n 9.3 k m s o u t h a n d 3.0 k m n o r t h of t h e t o w n of H o p l a n d .

T h e H . F . S . is a 1 8 9 0 - h a

agricultural

sciences r e s e a r c h facility l o c a t e d

ap­

proximately

160 k m

and

n o r t h of S a n F r a n c i s c o

6 4 k m i n l a n d f r o m t h e Pacific O c e a n .

It ranges in

e l e v a t i o n f r o m 1 5 3 - 9 1 4 m o n t h e w e s t e r n slopes of the M a y a c m a s Mountains.

T h e c l i m a t e is c h a r a c ­

t e r i z e d b y h o t , d r y s u m m e r s a n d cool, m o i s t w i n t e r s . S e v e n m a j o r v e g e t a t i o n a l t y p e s o c c u r t h e r e , 4 of which

(grass,

woodland-grass,

dense

woodland,

c h a p a r r a l ) c o m p r i s e 9 5 . 5 % of t h e t o t a l g r o u n d c o v e r ( H e a d y 1961).

T h e t o p o g r a p h y consists of r o l l i n g

hills i n t e r s p e r s e d w i t h r a v i n e s .

E i g h t e e n soil series

h a v e b e e n identified a n d described ( G o w a n s 1958). Sampling 0.093 m

2

and (=1

extraction 2

ft )

methods.

X 8-10 cm deep

Hundreds soil

of

samples

Downloaded from http://jme.oxfordjournals.org/ by guest on June 8, 2016

Abstract: Potential habitats of immature Tabanidae in southeastern Mendocino County, California, were investigated from March to July 1971-1973. Funnel extraction, handsorting and sieve methods were used to examine 3421 soil samples 0.093 m ( 1 ft ) X 8 -10 cm deep from 5 major semiaquatic habitats (in seepage areas and above the margins of creeks, permanent ponds, temporary ponds and the Russian River) and terrestrial habitats (oak woodland leaf litter and soil). These habitats are described and compared with respect to the density and diversity of their tabanid inhabitants. Semiaquatic sampling yielded 1437 larval and pupal tabanids of 15 species in 4 genera (7 Chrysops spp., 2 Hybomitra spp., 2 Silvias spp., 4 Tabanus spp.). Seepage areas ranked 1st as to density and diversity, yielding an average of 15.3 immatures/m of 7 species. Temporary pond margins yielded 14.4 immatures/m to rank 2nd, although only 1 /4 of those sampled were productive. The borders of creeks produced the lowest density (2.8 immatures/m ) and those of temporary ponds the lowest diversity (4 species). Woodland leaf litter and soil samples yielded no tabanid immatures, although they comprised over 40% of all samples. Other potential habitats sampled in which few or no tabanid immatures were found included decaying logs, stock water troughs and tree holes. Four of the 7 species of Chrysops reared were each restricted to 1 habitat type. Chrysops species were most abundant in habitats containing moderate to large amounts of decaying organic matter. The larvae of Hybomitra spp. "A" and "B" were associated with organic substrata, principally mosses. Immatures of both Siluiits species were collected from sand and silt above the margins of lotic habitats. Tabanus species were adapted to a variety of habitats, as larvae of 3 of the 4 species collected inhabited 2 or more habitat types. T. punctifer Osten Sacken occurred in every kind of natural semiaquatic habitat sampled except tree holes.

2

684

J. Med. Ent.

A d d i t i o n a l h a b i t a t s e x a m i n e d for t a b a n i d i m m a tures, b u t which could not be quantitatively compared

with

the

other

habitats

studied,

included

R u s s i a n R i v e r , l o c a t e d w e s t of t h e H . F . S . i n t h e Russian River valley, r a n k e d high a m o n g habitats a v a i l a b l e as p o t e n t i a l t a b a n i d b r e e d i n g sites. A.

Semiaquatic

habitats

1. Temporary pond margins. A p p r o x i m a t e l y 10 t e m p o r a r y p o n d s occurred on the H . F . S . a t elevations b e t w e e n 3 0 5 - 8 9 4 m . T h e s e p o n d s c o n t a i n e d surface runoff r a i n w a t e r from O c t o b e r or N o v e m b e r to M a y , J u n e , or J u l y . T h e d o m i n a n t plants living in t h e m were a n umbelliferous plant, Eryngium aristulatumjeps.; a r u s h , Juncus phaeocephalus E n g e l m . ; a n d a s p i k e r u s h , Eleocharis macrostachya B r i t t o n . I n v e r t e b r a t e s w e l l r e p r e s e n t e d i n soil s a m p l e s w e r e A c a r i ñ a , l a r v a e a n d a d u l t s of D y t i s c i d a e a n d H y d r o p h i l i d a e , a n d a d u l t s of H a l i p l i d a e ( C o l e ó p t e r a ) , a n d n e m a t o d e s . T h e soil t e x t u r e c o n s i s t e d of v a r y i n g p r o p o r t i o n s of c l a y a n d s a n d , a n d l a r g e q u a n t i t i e s of h u m u s . T w o of 3 t e m p o r a r y p o n d s t h a t d r i e d i n J u l y were p r o d u c t i v e for s e v e r a l species, whereas a p p a r e n t l y n o n e of t h e 7 p o n d s d r y i n g b y m i d - M a y produced tabanid immatures. T a b a n i d a s s o c i a t e s : Chrysops hirsuticallus Philip ( a q u a t i c a n d s e m i a q u a t i c ) , Hybomitra sp. " B " ( s e m i a q u a t i c ) , Tabanus punctifer O s t e n S a c k e n (semia q u a t i c ) , T. similis M a c q u a r t ( s e m i a q u a t i c ) .

algae or moss in creeks or on creek-fed w a t e r troughs, c a t t l e d r o p p i n g s , d e c a y i n g logs, stock w a t e r t r o u g h s , a n d tree holes. R e c o r d s w e r e k e p t of t h e f o l l o w i n g f r o m collecting

site:

number

extracted, n u m b e r teristics, a n d

of l a r v a e

and/or

of s a m p l e s t a k e n , soil

predominant

invertebrate

each pupae

charac-

associates

a n d p l a n t species. RESULTS

Classification

and description of

habitats

T h e t a b a n i d species f o u n d i n e a c h h a b i t a t

type

a r e listed after e a c h of t h e f o l l o w i n g h a b i t a t d e s c r i p tions.

F o r those larvae found in wet environments,

I have indicated in parentheses whether larvae were aquatic, semiaquatic, or both. The

relative

surface

area

potentially

available

for o c c u p a t i o n b y l a r v a l T a b a n i d a e o n t h e H . F . S . was

determined

from

a

survey

map.

The

area

r a n k i n g i n d e s c e n d i n g o r d e r w a s as follows: w o o d l a n d leaf

litter

and

soils,

temporary

creek

margins,

seepage areas, p e r m a n e n t p o n d margins, a n d temporary

pond

margins.

Although

habitat

space

a f f o r d e d b y t r e e h o l e s m a y h a v e e x c e e d e d t h a t of p e r m a n e n t a n d t e m p o r a r y p o n d s , tree holes a r e n o t ranked

because

satisfactory

their

estimation

inaccessibility of

their

total

precluded area.

a

The

TABLE 1. Tabanid fauna of Hopland, California, with indication of species reared during the present study and by previous workers. SPECIES

Apatolestes comastes var. willistoni Brennan Atylotus incisuralis (Macquart) Chrysops asbestos Philip C. clavicornis Brennan C. coloradensis Bigot C. coquilletti Hine C. hirsuticallus Philip C. pechumani Philip C. surdus Osten Sacken C. wileyae Philip Hybomitra aasa Philip H. californica (Marten) H. melanorhina (Bigot) H. procyon (Osten Sacken) Silvius gigantulus (Loew) S. notatus (Bigot) S. philipi Pechuman Tabanus aegrotus Osten Sacken T. kesseli Philip T. monoensis Hine T. punctifer Osten Sacken T. similis Macquart

IMMATURES REARED

none Webb & Wells (1924), Cameron (1926), Burger (1971) none present study present study present study present study present study present study present study none none none none none present study present study present study none Webb & Wells (1924), present study Webb & Wells (1924), Burger (1971), present study Roberts & Dicke (1964), Teskey (1969), Burger (1971), present study

Downloaded from http://jme.oxfordjournals.org/ by guest on June 8, 2016

w e r e t a k e n f r o m e a c h of 6 m a j o r s e m i a q u a t i c a n d terrestrial h a b i t a t types between M a r c h a n d J u l y 1971-1973, when m a n y larval tabanids at H o p l a n d were reaching maturity. Semiaquatic samples were t a k e n f r o m soil i n s e e p a g e a r e a s a n d g e n e r a l l y w i t h i n 1-2 m a b o v e t h e m a r g i n s of c r e e k s , p e r m a n e n t ponds, temporary ponds, a n d the Russian River. I m m a t u r e s were extracted from samples with 1.5-mm m e s h w i r e sieves, T u l l g r e n f u n n e l s , a n d b y h a n d sorting (with or without a h a n d cultivator). Select i o n of a s u i t a b l e e x t r a c t i o n t e c h n i q u e for e a c h h a b i t a t w a s b a s e d o n soil t e x t u r e a n d t y p e , a m o u n t of v e g e t a t i v e d e b r i s , a n d t h e a v a i l a b i l i t y of w a t e r . Since p r e l i m i n a r y s a m p l i n g revealed t h a t several Chrysops species w e r e a q u a t i c , s u b s e q u e n t s a m p l i n g a l o n g t h e m a r g i n s of t h e i r h a b i t a t s w a s t i m e d t o c o i n c i d e w i t h t h e p r e s e n c e of m a t u r e l a r v a e o r p u p a e a b o v e w a t e r l i n e (i.e., s a m p l i n g followed m i g r a t i o n of l a t e i n s t a r s a b o v e w a t e r m a r g i n s to p u p a t e ) . W o o d l a n d l e a f l i t t e r a n d soil s a m p l e s w e r e t a k e n b e n e a t h s t a n d s of o a k s , Quercus s p p . , o r m a d r o n e , Arbutus menziesii P u r s h , b y h a n d o r w i t h a h a n d cultivator or rake.

Vol. 12, no. 6

Lane:

1976

Immature Tabanidae, density and diversity

2 . Permanent pond margins. Three permanent p o n d s exist o n t h e H . F . S . a t e l e v a t i o n s b e t w e e n 305-403 m. T h e prevalent vegetation was as follows: c a t t a i l , Typha latifolia L . ; c o m m o n t u l e , Scirpus acutus M u h l . ; p o n d w e e d , Potamogetón nodosus P o i r . j a n d s p i k e r u s h , E. macrostachya. Soil s a m p l e s y i e l d e d e a r t h w o r m s , n e m a t o d e s , l a r v a e of c r a n e flies ( D i p t e r a : T i p u l i d a e ) , l o n g - l e g g e d flies ( D i p t e r a : Dolichopodidae), a n d adult Dytiscidae, H y d r o p h i l i d a e a n d S t a p h y l i n i d a e . T h e soil t y p e w a s loam with a high humus content. T a b a n i d a s s o c i a t e s : Chrysops clavicornis B r e n n a n ( a q u a t i c ) , C. coloradensis B i g o t ( a q u a t i c ) , C. surdus O s t e n S a c k e n ( s e m i a q u a t i c ) , Tabanus punctifer ( s e m i a q u a t i c ) a n d T. similis ( s e m i a q u a t i c ) .

T a b a n i d associates: a q u a t i c ) , Hybomitra s p . a q u a t i c ) , Silvius philipi T. aegrotus O s t e n S a c k e n Hine (semiaquatic), and

C. wileyae Philip (semi­ " A " (aquatic a n d semi­ P e c h u m a n (semiaquatic), ( s e m i a q u a t i c ) , T. monoensis T. punctifer ( s e m i a q u a t i c ) .

( s e m i a q u a t i c ) , C. pechumani P h i l i p ( a q u a t i c ) , C. wileyae ( s e m i a q u a t i c ) , Silvius notatus (Bigot) (semi­ a q u a t i c ) , S. philipi ( s e m i a q u a t i c ) , Tabanus punctifer (semiaquatic). 5. Seepage areas. T h i s t y p e of h a b i t a t c o n s i s t e d of surface w a t e r s e m a n a t i n g f r o m s p r i n g s o n g r a d ­ u a l l y s l o p i n g p a s t u r e s a n d hillsides. Seepages r a n k e d 2 n d i n t o t a l a r e a to c r e e k s a m o n g w e t habitats o n the H . F . S . from O c t o b e r or N o v e m b e r to M a y o r J u n e . P l a n t s w h i c h g r e w i n n a t u r a l s e e p a g e s w e r e as follows: g r a s s e s ; mosses, Bryum s p . , Pohlia nutans ( H e d w . ) L i n d b . ; a n d r u s h e s , Juncus s p p . S c a t t e r e d t h r o u g h o u t t h e H . F . S . w e r e 41 semiartificial seepages c r e a t e d b y spillage from s p r i n g - f e d stock w a t e r t r o u g h s . A b o u t 9 0 % of these seepages w e r e p e r m a n e n t . In contrast, the surfaces of m a n y n a t u r a l s e e p a g e s d r i e d b y M a y o r June. I n addition to the above vegetation, water­ cress, Nasturtium officinale R . Br., often g r e w i n semiartificial seepages. T h e p r e d o m i n a n t inver­ t e b r a t e associates f o u n d i n s e e p a g e s w e r e l a r v a l C e r a t o p o g o n i d a e ( D i p t e r a ) a n d s t r a t i o m y i d s ; lesser n u m b e r s of d o l i c h o p o d i d a n d t i p u l i d l a r v a e w e r e also p r e s e n t . Soil w i t h i n a n d s u r r o u n d i n g m a n y s e e p a g e s w a s mixed with cattle a n d sheep droppings. Large q u a n t i t i e s of h u m u s w e r e p r e s e n t i n s e e p a g e soils. T a b a n i d a s s o c i a t e s : Chrysops clavicornis, C. surdus, C. wileyae, Hybomitra s p . " A , " Tabanus monoensis, T. punctifer, T. similis. B.

Terrestrial

1.

Woodland

Russian River banks.

through Hopland

T h e Russian River

flows

litter

and soil.

Oaks,

douglasii H . & A . , Q. lobata N e é , Q. wislizenii and

Q.

menziesii,

kelloggii

Newb.;

and

madrone,

I n v e r t e b r a t e s f o u n d a t t h e l e a f litter-soil were

centipedes,

Coleóptera

larvae

Rhagio

and

Symphoromyia

inconspicua

Turner

(Diptera). &

One

Chillcott

T h e l o a m y soil i n w o o d e d a r e a s w a s w i t h leaf l i t t e r u p t o s e v e r a l c m i n d e p t h .

C.

Miscellaneous

1.

Tree

Carabidae,

carpeted

T a b a n i d associates: n o n e found.

Coleopteran

(e.g.,

5

californica

B e n t h . ; a n d w i l l o w s , Salix spp.-, g r e w a l o n g its b a n k s . adults

Symand

Rhagio l a r v a e w e r e r e a r e d .

I t is t h e o n l y Cotton­

adults,

earthworms, a n d larval R h a g i o n i d a e in the genera

approximately

W a t s . ; g r a p e , Vitis

interface

and

a t a d i s t a n c e of

w o o d , Populus fremontii

Arbutus H.F.S.

A grass u n d e r s t o r y is a s s o c i a t e d w i t h this h a b i t a t .

7 k m from the H . F . S . h e a d q u a r t e r s .

river in southeastern M e n d o c i n o C o u n t y .

Quercus A. D C .

cover extensive acreages on the

phoromyia 4.

habitat leaf

Omophro-

holes.

habitats This

habitat

was

common

in

n i d a e ) , t i p u l i d l a r v a e , e a r t h w o r m s a n d slugs w e r e

wooded areas.

e x t r a c t e d f r o m soil s a m p l e s .

m o i s t v e g e t a t i v e d e b r i s f r o m l a t e fall to l a t e s p r i n g .

t h e m a j o r soil c o m p o n e n t s .

S a n d a n d silt w e r e H u m u s was present in

small a m o u n t s . Tabanid

associates:

Chrysops

coquilletti

Hine

Some contained

M o s t tree holes c o n t a i n e d w a t e r or water year-round,

whereas

most

of t h e 3 0 t h a t w e r e s a m p l e d i n M a y o r J u n e

had

recently

and

dried.

Millipedes,

tipulid

larvae,

Downloaded from http://jme.oxfordjournals.org/ by guest on June 8, 2016

3. Creek margins. N u m e r o u s s m a l l c r e e k s flow d o w n w a r d from the M a y a c m a s M o u n t a i n s t o w a r d the Russian River basin. Creeks on the H . F . S . d r i e d b e t w e e n M a y a n d J u l y . M o s t creeks s a m p l e d w e r e t e m p o r a r y , b u t 2 p e r m a n e n t creeks located off t h e H . F . S . w e r e also s a m p l e d . T h e p r e d o m i n a n t p l a n t s w e r e as follows: C a l i f o r n i a b a y , Umbellularia californica ( H . & A . ) N u t t . ; o a k s , Quercus s p p . ; g r a s s e s ; h o r s e t a i l , Equisetum; mosses; a n d rushes, Juncus s p p . M o s s e s g r e w o n r o c k s i n c r e e k s b o t h above a n d below waterline. T h e y became dry d u r i n g the late spring as creeks d r i e d u p . Earth­ worms, staphylinid adults, a n d larval Stratiomyidae (Diptera) a n d tipulids were observed in samples. T h e soil t e x t u r e w a s a m i x t u r e of s a n d , silt a n d g r a v e l . S m a l l a m o u n t s of h u m u s w e r e p r e s e n t i n soil e x c e p t a r o u n d v e g e t a t i o n w h e r e t h e r e w e r e m o d e r a t e q u a n t i t i e s . T h e l a c k of h u m u s m a y h e l p t o e x p l a i n t h e l o w d e n s i t i e s a n d d i v e r s i t y of i m m a ­ t u r e Chrysops a l o n g c r e e k m a r g i n s as m o s t Chrysops larvae are presumably saprophagous.

685

Vol. 12, no. 6

J . Med. Ent.

686

TABLE 2. Average density and diversity of larvae and pupae of Tabanidae collected from 6 major habitats in southeastern Mendocino County, California, during 1971-1973. Samples were taken between March and July when most tabanid larvae were approaching, or had already attained, matu­ rity. NUMBER OF M SAMPLED*

MEAN NUMBER OF IMMATURES/M

142.0 21.3

0.0 15.3

0 7

48.8 29.9 32.8 43.4 318.2

2.8 6.1 14.4 7.4 4.5

6 5 4 6 15

2

HABITAT

Woodland leaf litter and soil Seepage areas Banks (margins) of: Creeks Permanent ponds Temporary ponds Russian River Totals

No. OF SPECIES

J

2

•Converted from 0.093-m samples.

invertebrates holes.

obtained

from

dried

or

moist

tree

T r e e holes c o n t a i n i n g w a t e r yielded l a r v a e

of c e r a t o p o g o n i d s , S y r p h i d a e ( D i p t e r a ) , a n d l a r v a e

4. Cattle droppings. A p p r o x i m a t e l y 55 r a n g e cattle were present o n the H . F . S . e a c h year from M a r c h or April to late J u n e . T h e i r droppings were a b u n d a n t i n l o c a l i z e d a r e a s , e.g., n e a r c e r t a i n p o n d s a n d s e e p a g e a r e a s . L a r v a e of a n anthomyiid (Scatophaga), a n d t h e face fly (Musca autumnalis DeGeer), and adult Scarabaeidae a n d Staphylinidae ( C o l e ó p t e r a ) w e r e o b s e r v e d i n o r b e n e a t h s o m e of the approximately 40 cattle droppings examined. O n e Tabanus punctifer l a r v a w a s f o u n d b e n e a t h c o w d u n g a l o n g t h e m a r g i n of a s e e p a g e a r e a . 5. Decaying logs. A d e c a y i n g l o g p a r t i a l l y s u b ­ m e r g e d a l o n g the m a r g i n of a t e m p o r a r y p o n d y i e l d e d 1 Hybomitra s p . " B " l a r v a . A n t s ( H y m e n o p tera: Formicidae) and 3 pupal Muscidae (Diptera) i n h a b i t e d t h e s a m e l o g . N i n e o t h e r d e c a y i n g logs, b u t n o t necessarily partially s u b m e r g e d ones, produced no tabanid immatures.

a n d p u p a e of t h e w e s t e r n t r e e - h o l e m o s q u i t o , Aedes sierrensis ( L u d l o w ) ( D i p t e r a : C u l i c i d a e ) .

T r e e holes

yielded no tabanid immatures. 2.

Algae

in creeks.

Shallow

temporary

creeks

c o n t a i n e d s c a t t e r e d p a t c h e s of a f i l a m e n t o u s g r e e n alga that was sampled sporadically. 1 Chrysops

wileyae

larvae

well

as

pupa as

and

2

oligochaetes,

Algae yielded

Tabanus

monoensis

Ephemeroptera

n y m p h s , dytiscid a n d stratiomyid larvae. 3.

Algae

or moss on water troughs beneath

drainage pipes.

6. Stock water troughs. E l e v e n of t h e 41 s t o c k water troughs present on the H.F.S. were examined. A d e a d l a r v a b e l i e v e d t o b e Tabanus monoensis w a s the only t a b a n i d found. Faunal density and

T h e known H o p l a n d tabanid fauna based adult

A b r o w n a l g a c o l o n i z i n g a creek-fed

trapping

studies

conducted

over

of o n l y 4 ( 1 8 . 2 % ) h a v e b e e n d e s c r i b e d h e r e t o f o r e ,

Ephemeroptera

T. punctifer a n d T.

tera),

tipulid

T A B L E 3.

larvae,

and

larvae

staphylinid

(Dip­

adults.

A

A

monoensis,

similis.

t o t a l of 3 1 8 . 2 m

2

of soil, r e p r e s e n t i n g

Larval habitats of tabanid species collected from southeastern Mendocino County, California, during 1971-1973. BANKS (MARGINS) OF POND SPECIES

Chrysops clavicornis C. coloradensis C. coquilletti C. hirsuticallus C. pechumani C. surdus C. wileyae Hybomitra sp. "A" H. sp. "B" Silvias notatus S. philipi Tabanus aegrotus T. monoensis T. punctifer T. similis

SEEPAGES

Creeks

(Temporary) (Permanent)

River

X X

X

X X X X X X

X X

X X X

X X X

in

O f t h e 2 2 species listed, i m m a t u r e stages

i.e., Atylotus incisuralis ( M a c q u a r t ) , Tabanus

Simuliidae

upon 6-year

a n d o n m y r e a r i n g s t u d i e s is p r e s e n t e d

T A B L E 1.

m e t a l w a t e r t r o u g h y i e l d e d 1 T. monoensis l a r v a a n d nymphs,

a

period (Anderson, Olkowski, H o y & Lane, unpubl. data)

creek-fed

diversity

X X X X

X X

X X

X X

X

3421

Downloaded from http://jme.oxfordjournals.org/ by guest on June 8, 2016

o t h e r fly l a r v a e ( C y c l o r r h a p h a ) w e r e t h e p r i n c i p a l

w o o d e n w a t e r t r o u g h c o v e r e d b y m o s s p r o d u c e d 11 T. monoensis l a r v a e .

687

Lane : Immature Tabanidae, density and diversity

1976

2

TABLE 4.

Comparison of the average density (numbers/10 m ) of tabanid immatures collected from 1 habitat type in southeastern Mendocino County, California, during 1971-1973.* BANKS (MARGINS) OF

SPECIES

Creek

Temporary pond

Chrysops hirsuticallus C. pechumani C. coloradensis C. coquilletti Silvius notatus Hybomitra sp. " B " Tabanus aegrotus 2.3 •Converted from 0.093-m samples.

River

Permanent pond

134.2 24.8 22.8 9.9 34.6 5.2

2

2

2

2

2

2

TABLE 5.

s e m i a q u a t i c h a b i t a t . T h r e e of t h e 6 species f o u n d a l o n g r i v e r b a n k s a n d 2 of t h e 4 species o b t a i n e d from t e m p o r a r y p o n d margins were restricted to t h o s e h a b i t a t s . H o w e v e r , all 7 species b r e e d i n g i n s e e p a g e a r e a s b r e d i n a t least 1 o t h e r h a b i t a t t y p e . Chrysops hirsuticallus occurred in considerably h i g h e r d e n s i t y ( 1 3 4 . 2 / 1 0 m ) t h a n all o t h e r species f o u n d i n 1 h a b i t a t t y p e (TABLE 4). Silvius notatus r a n k e d 2 n d a n d Tabanus aegrotus r a n k e d last. 2

O f t h o s e species o c c u r r i n g i n 2 o r m o r e h a b i t a t t y p e s (TABLE 5), Chrysops surdus m a n i f e s t e d t h e h i g h e s t o v e r a l l d e n s i t y ( 2 7 . 9 / 1 0 m ) a n d C. wileyae ( 1 . 3 / 1 0 m ) t h e lowest. F u r t h e r , C. surdus w a s significantly m o r e n u m e r o u s i n s e e p a g e s t h a n a l o n g t h e m a r g i n s of p e r m a n e n t p o n d s . Six of t h e 7 species f o u n d i n 1 h a b i t a t t y p e r a n k e d e i t h e r 1st, 2 n d , o r 3 r d i n a b u n d a n c e w i t h i n t h e i r r e s p e c t i v e h a b i t a t s (TABLE 6). F o u r of t h e s e species w e r e Chrysops. A m o n g the 8 species w h i c h b r e d i n 2 o r m o r e k i n d s of h a b i t a t s , C. clavicornis r a n k e d 1st for p e r m a n e n t p o n d s , C. surdus 1st for s e e p a g e a r e a s , a n d Hybomitra s p . " A " 1st for c r e e k m a r g i n s . T. punctifer r a n k e d n o h i g h e r t h a n 3 r d i n a n y habitat type. T. similis r a n k e d l a s t o r n e x t t o last i n e a c h of t h e 3 h a b i t a t t y p e s it o c c u p i e d . 2

2

DISCUSSION

Summary

of faunal

density

and diversity

in

2

Comparison of the average density (numbers/10 m ) of tabanid immatures collected from more than 1 habitat type in southeastern Mendocino County, California, during 1971-1973.* BANKS (MARGINS) OF

Creek

SPECIES

Temporary pond

Permanent pond

River

24.7 0.7

Chrysops clavicornis** C. surdus C. wileyae Hybomitra sp. "A" Silvius philipi Tabanus monoensis T. punctifer T. similis

0.4 9.8 8.0 5.4 0.8 J

2.6

SEEPAGE

TOTALS

1.4 66.2 0.5 12.3

15.0 27.9 1.3 10.6 4.3 21.7 3.7 1.5

0.2 2.8 1.8

11.8 1.3

1.8

59.2 4.7 1.4

•Converted from 0.093-m samples. ** Density data for C. clavicornis and C. wileyae obtained from seepage areas are low because their larvae were inseparable during the early stages of this study, and 15 larvae of 1 or both of these species are not included here.

various

Downloaded from http://jme.oxfordjournals.org/ by guest on June 8, 2016

s a m p l e s of 0 . 0 9 3 m e a c h , w a s e x a m i n e d f r o m 6 m a j o r h a b i t a t t y p e s (TABLE 2). T h u s , a n a v e r a g e of 5 3 . 1 m of soil w a s s e a r c h e d p e r h a b i t a t t y p e , w i t h a r a n g e of 2 1 . 3 - 1 4 2 . 0 m . T h e s e s a m p l e s y i e l d e d 1437 t a b a n i d l a r v a e a n d p u p a e of 15 species in 4 genera. O f t h e 13 species I r e a r e d , 10 ( 7 6 . 9 % ) h a d not been previously reared. Overall rearing success w a s 5 2 . 7 % . S e e p a g e a r e a s r a n k e d 1st w i t h r e s p e c t t o b o t h a v e r a g e d e n s i t y a n d d i v e r s i t y of i m m a t u r e s (TABLE 2), y i e l d i n g a n a v e r a g e of 15.3 i m m a t u r e s / m of 7 species i n 3 g e n e r a . T e m p o r a r y p o n d m a r g i n s y i e l d e d 14.4 i m m a t u r e s / m t o r a n k 2 n d i n d e n s i t y , b u t p r o d u c e d t h e l o w e s t species d i v e r s i t y a m o n g s e m i a q u a t i c h a b i t a t s . T h e m a r g i n s of r i v e r s a n d p e r m a n e n t p o n d s r a n k e d 3 r d a n d 4th, respectively, as t o d e n s i t y , y i e l d i n g a b o u t 1 / 2 as m a n y i m m a t u r e s as t e m p o r a r y p o n d s . T h e b a n k s of t h e R u s s i a n R i v e r a n d c r e e k m a r g i n s r a n k e d 2 n d i n species d i v e r s i t y w i t h 6 species e a c h , w h e r e a s p e r m a n e n t p o n d s y i e l d e d 5 species. C r e e k m a r g i n s p r o d u c e d t h e lowest density. F o u r of t h e 7 Chrysops species w e r e f o u n d w i t h i n 1 h a b i t a t t y p e (TABLE 3). B o t h Silvius species w e r e f o u n d a l o n g t h e b o r d e r s of l o t i c h a b i t a t s . Every Tabanus species, e x c e p t for T. aegrotus, o c c u p i e d a t least 2 s e m i a q u a t i c h a b i t a t s . T. punctifer w a s t h e o n l y species c o l l e c t e d f r o m e v e r y m a j o r t y p e of

Vol. 12, no. 6

J. Med. Ent.

688

Comparison

with

previous

North

American

works.

2

a b o u t 1200 a n d a v e r a g e d a b o u t 5 l a r v a e / f t ( — 0.093 m ). M e r r i t t (1974) f o u n d n o t a b a n i d l a r v a e a m o n g t h e i n s e c t i n h a b i t a n t s of 7 9 8 c a t t l e d r o p p i n g s h e s a m p l e d f r o m t h e S i e r r a N e v a d a foothills of California. I c o l l e c t e d 1 Tabanus punctifer l a r v a f r o m a c a t t l e d r o p p i n g a l o n g t h e m a r g i n of a p e r m a n e n t seepage area. 2

Wilson (1969) d e t e r m i n e d p o p u l a t i o n densities of l a r v a l t a b a n i d s i n h a b i t i n g forest floor, o p e n p a s t u r e , stock p o n d s a n d s t r e a m m a r g i n s i n s o u t h e r n Louisiana. T h e forest floor y i e l d e d f r o m 0 t o m o r e t h a n 1 l a r v a / f t of soil s u r f a c e a t v a r i o u s sites, a n d w a s t h e p r i m a r y l a r v a l h a b i t a t of t h e m o r e a b u n d a n t species. I s a m p l e d 142 m of l e a f l i t t e r a n d soil from wooded areas a n d found no t a b a n i d larvae. 2

2

T h o m p s o n ( 1 9 7 0 ) c o m p a r e d t a b a n i d larval collec­ tions from a m a p l e s w a m p b e d , a s t r e a m b a n k , a n d a p o n d m a r g i n in N e w Jersey. T h e p o n d m a r g i n y i e l d e d 4 species a n d 8 3 % of all l a r v a e a n d p u p a e collected. T h o m p s o n (1971) subsequently c o m ­ p a r e d a s w a m p bed, p o n d m a r g i n s a n d river banks in M a r y l a n d . T h e swamp bed produced greater n u m b e r s a n d d i v e r s i t y (7 species) of t a b a n i d i m ­ matures than the other habitats. B u r g e r (1971) f o u n d t h a t c r e e k s s u p p o r t e d t h e g r e a t e s t d i v e r s i t y (10 species) of l a r v a l t a b a n i d s i n A r i z o n a . H e n o t e d t h a t creeks s u p p o r t i n g a t a b a n i d fauna must be p e r m a n e n t or dry u p only during very d r y y e a r s . H o w e v e r , t h e m a r g i n s of t e m p o r a r y c r e e k s a t H o p l a n d y i e l d e d l o w n u m b e r s of 6 species a l t h o u g h m o s t c r e e k s w e r e d r y for a p p r o x i m a t e l y 1/3 of t h e y e a r . Ellis & H a y s (1973) i n v e s t i g a t e d p o p u l a t i o n d e n s i t i e s of t a b a n i d l a r v a e b r e e d i n g a t 2 f a r m p o n d s in A l a b a m a . A t o t a l of 4 8 6 soil s a m p l e s 1 ft t a k e n a l o n g t h e m a r g i n s a t b o t h sites y i e l d e d a n a v e r a g e of 4 . 0 2 Chrysops a n d Tabanus l a r v a e / f t . Permanent p o n d m a r g i n s a t H o p l a n d p r o d u c e d a n a v e r a g e of 6.1 t a b a n i d i m m a t u r e s / m of 5 species i n 2 g e n e r a (3 Chrysops, 2 Tabanus). 2

2

2

Summary

taining moderate concerning

i n m a r s h y a r e a s a n d i n w e t soil a b o v e t h e e d g e s of

1936).

an

irrigation

ditch,

sloughs

and

a

lake.

Their

t h a t T. punctifer l a r v a e w e r e m o s t a b u n d a n t

a l o n g t h e m a r g i n s of t h e l a k e a g r e e s w i t h

results

r e p o r t e d h e r e i n (TABLE 5 ) . Gingrich & Hoffman Tabanus

habitat

distributions.

Larval

their

t o l a r g e q u a n t i t i e s of

decaying

This coincides w i t h earlier reports presumed

feeding

habits

(Segal

O f t h e Tabanus species f o u n d , 1/2 w e r e m o s t

p r e v a l e n t a b o v e t h e e d g e s of p o n d s ; t h e o t h e r were found margins.

in seepage areas a n d / o r

along

1/2

creek

Tabanus species w e r e a d a p t e d t o a w i d e r

r a n g e of h a b i t a t s t h a n w e r e Chrysops species.

(1967) c o l l e c t e d l a r v a e of

atratus F a b r i c i u s a n d

larval

organic matter.

W e b b & W e l l s (1924) f o u n d Tabanas punctifer l a r v a e

finding

of

Chrysops w e r e m o s t a b u n d a n t i n w e t h a b i t a t s c o n ­

T. subsimilis

Bellardi

Hybomitra

spp. " A " a n d " B " were associated with

s u b s t r a t a c o n s i s t i n g of o r g a n i c m a t t e r ,

f r o m t h e effluent of fecal d e b r i s f r o m a d a i r y b a r n .

mosses, a

T h e y estimated that the total t a b a n i d population was

T e s k e y ( 1 9 6 9 ) for m o s t k n o w n Hybomitra

finding

principally

consistent with t h a t reported

by

l a r v a e in

Downloaded from http://jme.oxfordjournals.org/ by guest on June 8, 2016

habitats. Seepage areas yielded higher densities a n d m o r e species t h a n t h e o t h e r h a b i t a t s s t u d i e d , b u t t h e i r s u i t a b i l i t y for i m m a t u r e t a b a n i d s v a r i e d a c c o r d i n g t o t h e i r d e g r e e of p e r m a n e n c y . Per­ m a n e n t s e e p a g e s y i e l d e d 7 species, i n c l u d i n g h i g h d e n s i t i e s of 2 species, w h e r e a s t e m p o r a r y s e e p a g e s y i e l d e d r e l a t i v e l y l o w n u m b e r s of 1 species, Hybomitra sp. " A . " T h e m a r g i n s of t e m p o r a r y c r e e k s s u p p o r t e d t h e l o w e s t d e n s i t y a n d t h o s e of t e m p o r a r y p o n d s t h e least species d i v e r s i t y . A s c a r c i t y of s u i t a b l e o v i p o s i t i o n sites (i.e., e m e r g e n t v e g e t a t i o n a b o v e w a t e r o r m o i s t soil) a p p a r e n t l y w a s o n e c r i t i c a l f a c t o r r e s p o n s i b l e for t h e l o w d e n s i t i e s of t a b a n i d i m m a t u r e s along creek margins. T e m p o r a r y p o n d s c o n t a i n e d m o d e r a t e to large stands of e m e r g e n t v e g e t a t i o n , b u t 7 of 10 s u c h p o n d s d r i e d b y m i d - M a y b e f o r e a d u l t s of m o s t t a b a n i d species h a d e m e r g e d . T h e r e a f t e r , r a p i d l y d i m i n i s h i n g surface soil m o i s t u r e a n d g r a z i n g b y livestock m a y h a v e l i m i t e d s u b ­ sequent oviposition by tabanids. A l t h o u g h o v e r 4 0 % of t h e s a m p l e s w e r e t a k e n f r o m w o o d l a n d l e a f l i t t e r a n d soil, n o i m m a t u r e s w e r e found in these substrata. T h i s does not p r o v i d e c o n c l u s i v e e v i d e n c e , h o w e v e r , t h a t n o n e of the H o p l a n d tabanids b r e d in terrestrial habitats. T h e v a s t n e s s of t e r r e s t r i a l h a b i t a t s r e l a t i v e to semiaquatic habitats precluded sampling compara­ b l e p o r t i o n s of t h e f o r m e r . O f t h e 9 species t h a t w e r e n o t r e a r e d d u r i n g this s t u d y b u t w h i c h h a v e b e e n t a k e n as a d u l t s o n t h e H . F . S . , o n l y Atylotus incisuralis h a s b e e n r e a r e d p r e v i o u s l y (TABLE l ) . W e b b & W e l l s ( 1 9 2 4 ) , C a m e r o n (1926) a n d B u r g e r (1971) r e a r e d l a r v a e of A. incisuralis o b t a i n e d f r o m s e v e r a l k i n d s of w e t h a b i t a t s . L a r v a e of Hybomitra s p p . " A " a n d " B , " w h i c h p r e s u m a b l y r e p r e s e n t 2 of t h e 4 k n o w n Hybomitra species (TABLE l ) , w e r e b o t h f o u n d i n s e m i a q u a t i c h a b i t a t s . L a r v a e of t h e s e species fed well a n d g r e w r a p i d l y until they a p p r o a c h e d m a t u r i t y w h e n they usually s u c c u m b e d to some u n k n o w n c a u s e . T h r e e l a r v a e of Hybomitra sp. " B " p u p a t e d b u t died soon thereafter.

689

Lane : Immature Tabanidae, density and diversity

1976

TABLE 6. Ranking of immature tabanids with respect to their average densities (1 == highest density) within 5 major habitat types in southeastern Mendocino County, California, from March to July 19711973. POND

Chrysops clavicomis C. coloradensis C. coquilletti C. hirsuticallus C. pechumani C. surdus C. wileyae Hybomitra sp. "A" H. sp. "B" Silvius notatus S. philipi Tabanus aegrotus T. monoensis T. punctifer T. similis

5

5

1 7 3

4

6 1 2

1 6

2 4 3 5

3 4

apparently

restricted

to

1

habitat type, whereas others were found in 2 or m o r e h a b i t a t t y p e s (TABLE 4, 5 ) .

O f t h o s e species o b ­

3 4

2 4 5

5

s a m e h a b i t a t t y p e a t d i f f e r e n t sites o r t i m e s of t h e y e a r d e p e n d i n g u p o n l o c a l v a r i a t i o n i n soil t y p e , m o i s t u r e levels, a n d a m o u n t of v e g e t a t i v e d e b r i s present. This procedure m a y have eliminated some of t h e b i a s w h i c h w o u l d h a v e o c c u r r e d h a d all 3 t e c h n i q u e s b e e n u s e d solely for s a m p l i n g different h a b i t a t t y p e s , o r h a d 1 t e c h n i q u e b e e n u s e d to s a m p l e all h a b i t a t s . L a n e (1974) f o u n d t h a t a 1 . 5 - m m m e s h w i r e sieve w a s m o r e efficient t h a n T u l l g r e n funnels for e x t r a c t i n g k n o w n n u m b e r s of Chrysops hirsuticallus f r o m p o n d soil a t b o t h h i g h (20 l a r v a e / 0 . 0 9 3 m ) a n d l o w (10 l a r v a e / 0 . 0 9 3 m ) l a r v a l d e n s i t i e s . T h e s e differences w e r e s i g n i f i c a n t ( p < 0 . 0 5 ) a t t h e h i g h d e n s i t y . F u r t h e r s t u d i e s c o m p a r i n g t h e effi­ c i e n c y of t h e s e a n d o t h e r m e t h o d s for e x t r a c t i n g t a b a n i d i m m a t u r e s f r o m different soil t y p e s a r e needed. O n e p r o b l e m i n c o m p a r i n g t h e s u i t a b i l i t y of different s e m i a q u a t i c h a b i t a t s for s e v e r a l t a b a n i d species is t h a t s o m e species a r e a q u a t i c for m o s t of t h e i r l a r v a l life. L a r v a e of 4 a q u a t i c Chrysops species d i d n o t m i g r a t e a b o v e w a t e r l i n e u n t i l t h e y a p p r o a c h e d m a t u r i t y . A n otherwise suitable semia q u a t i c h a b i t a t might, therefore, yield n o i m m a t u r e s if s a m p l e d p r e m a t u r e l y o r after a d u l t s h a d e m e r g e d . This problem was complicated by yearly fluctuating weather conditions which caused variation in larval migration a n d adult emergence times. S y s t e m a t i c s a m p l i n g of t h e i m m a t u r e s of C. hirsutical­ lus o v e r a 1 5 - m o n t h p e r i o d r e v e a l e d s e a s o n a l v a r i a ­ t i o n s i n d e n s i t y a b o v e a n d b e l o w t h e m a r g i n of a t e m p o r a r y p o n d ( L a n e 1974). 2

tained from 1 h a b i t a t t y p e , Chrysops hirsuticallus

and

2

Hybomitra

sp. " B " w e r e physiologically a d a p t e d

s u r v i v e p r o l o n g e d p e r i o d s of s u r f a c e d r o u g h t . a q u a t i c l a r v a e of C. pechumani

have well-developed

pseudopodia w h i c h seem to be a n a d a p t a t i o n clinging

to the undersides

to

The

of o b j e c t s

to

for

prevent

their being swept a w a y b y river currents.

Promi­

n e n t p s e u d o p o d i a a r e also p r e s e n t i n t h e

aquatic

l a r v a e of Atherix variegata W a l k e r ( D i p t e r a : R h a g i o n i d a e ) a n d species i n t h e s u b f a m i l i e s

Clinocerinae

and Hemerodromiinae (Diptera: Empididae) (Wirth & Stone 1968). T h e c a t h o l i c b r e e d i n g h a b i t s of T. punctifer

have

b e e n r e p o r t e d b y W e b b & W e l l s (1924) a n d B u r g e r ( 1 9 7 1 ) , a n d r e c o n f i r m e d i n this s t u d y . Limitations

of sampling

the sampling program funnel

extraction,

program.

A deficiency

was that 3 methods

handsorting

and

sieving)

of

(i.e., were

u s e d w h o s e r e l a t i v e efficiencies for e x t r a c t i n g i m m a tures

from

different

soil

types

were

unknown.

Several extraction m e t h o d s were used because n o n e b y itself w a s f o u n d t o b e s u i t a b l e for s a m p l i n g all 6 h a b i t a t types e x a m i n e d .

Further, more than 1

m e t h o d w a s s o m e t i m e s u s e d t o s a m p l e soil f r o m

the

T h e s e difficulties w e r e m i n i m i z e d b y u s i n g p r e ­ liminary larval a n d a d u l t sampling d a t a to establish a semiaquatic collecting schedule t i m e d to concur

Downloaded from http://jme.oxfordjournals.org/ by guest on June 8, 2016

were

SEEPAGE

3

America.

species

RIVER

1

Silvius l a r v a e w e r e o b t a i n e d a b o v e t h e b o r d e r s of lotic h a b i t a t s . S. notatus i n h a b i t e d s a n d a n d silt a l o n g t h e b a n k s of t h e R u s s i a n R i v e r , a n d S. philipi inhabited similar substrata along creek margins or r i v e r b a n k s . I n A r i z o n a , B u r g e r (1971) c o l l e c t e d l a r v a e of S. quadrivittatus ( S a y ) i n d a m p silt a l o n g t h e b a n k s of d e s e r t r i v e r s . Some

(Permanent) 1 2

CM

eastern N o r t h

(Temporary)

CREEK

SPECIES

J. Med. Ent.

690

w i t h t h e l a t e - i n s t a r p e r i o d of m o s t species. I t w a s f o u n d t h a t l a r v a e of s o m e species r e a c h e d m a t u r i t y i n M a r c h a n d / o r A p r i l [e.g., Hybomitra procyon ( O s t e n S a c k e n ) , Chrysops pechumani], w h e r e a s l a r v a e of o t h e r species r e a c h e d m a t u r i t y d u r i n g t h e s u m m e r months (e.g., Tabanus monoensis, T. punctifer). F u r t h e r , h u n d r e d s of 0 . 0 9 3 - m s a m p l e s w e r e t a k e n from every semiaquatic h a b i t a t type. T h u s , the d e n s i t y d a t a p r e s e n t e d h e r e i n p r o v i d e a fairly a c c u r a t e p i c t u r e of r e l a t i v e p o p u l a t i o n d e n s i t i e s w i t h i n these habitats, prior to most adult emergence, a n d for t h e seasons s a m p l e d . 2

Acknowledgments: Mr A. H. Murphy, Supervisor, and staff of the University of California Hopland Field Station, are gratefully acknowledged for their assistance in various aspects of the study. I thank Drs J. R. Anderson, W. W. Middlekauff and J. A. Powell, Department of Entomological Sciences, and Dr D. C. Erman, Department of Forestry and Conservation, University of California, Berkeley, for reviewing the manuscript. I also thank Dr L. L. Pechuman, Department of Entomology, Cornell University, Ithaca, New York, and Dr C. B. Philip, Department of Entomology, California Academy of Sciences, San Francisco, for their taxonomic advice, and Mr P. Rubtzoff, Department of Entomological Sciences, University of California, Berkeley, for determining most of the plant species mentioned herein. L I T E R A T U R E CITED

Anderson, J. R., W. Olkowski & J. B. Hoy. 1974. The response of tabanid species to CO -baited insect flight traps in northern California (Díptera: Tabanidae). PanPacif. Ent. 50: 255-68. Bailey, N. S. 1948. A mass collection and population survey technique for larvae of Tabanidae (Díptera). Bull. Brooklyn Ent. Soc. 43: 22-29. Brimley, C. S. 1911. Notes on the life histories of Tabanidae (Díptera). Ent. News 22: 133. Burger, J. F. 1971. The biology and taxonomy of immature Arizona Tabanidae (Díptera). Ph.D. dissertation, Univ. of Arizona, Tucson. 158 p. Cameron, A. E. 1926. Bionomics of the Tabanidae (Díptera) of the Canadian prairie. Bull. Ent. Res. 17: 1-42. a

Ellis, H. C. & K. L. Hays. 1973. Population densities of tabanid larvae in two farm pond habitats in east central Alabama. Florida Ent. 56: 11-14. English, Kathleen M. I. 1955. Notes on the morphology and biology of Scaptia vicina Tayl. and a new species of Scaptia (Diptera, Tabanidae). Proc. Linn. Soc. N. S. W. (1954) 79: 219-29. Freeman, J. V. & E. J. Hansens. 1972. Collecting larvae of the salt marsh greenhead Tabanus nigrovittatus and related species in New Jersey: comparison of methods. Environ. Ent. 1: 653-58. Gingrich, R. E. & R. A. Hoffman. 1967. Abundance and survival of tabanid larvae in effluent from a dairy barn. Ann. Ent. Soc. Amer. 60: 72-74. Gowans, K. D. 1958. Soil survey of the Hopland Field Station. Calif. Agr. Exp. Sta. 34 p. Heady, H. F. 1961. Ecological researchfindingson the annual grass type at the Hopland Field Station. Calif. Forestry and Forest Products. No. 24. 4 p. Jamnback, H. & W. Wall. 1959. The common salt-marsh Tabanidae of Long Island, New York. Bull. N. Y. St. Mus. Sei. Serv. 375. 77 p. Knudsen, A. B. & D. M. Rees. 1968. Methods used in Utah for sampling tabanid populations. Mosquito News 28: 356-61. Lane, R. S. 1974. The biology and taxonomy of immature Tabanidae from Mendocino County, California, with an autecological study of Chrysops hirsuticallus Philip (Diptera: Tabanidae). Ph.D. dissertation, Univ. of Calif., Berkeley. 266 p. Merritt, R. W. 1974. The species diversity and abundance of insects inhabiting catüe droppings and their role in the degradation of dung in four different pasture and rangeland ecosystems in the Sierra Nevada foothills of California. Ph.D. dissertation, Univ. of Calif., Berkeley. 273 p. Philip, C. B. 1973. A remarkable tabanid inhabitant of an ant nest in western Washington—natural or accidental ? Pan-Pacif. Ent. 49: 82. Roberts, R. H. & R. J. Dicke. 1964. The biology and taxonomy of some immature Nearctic Tabanidae (Diptera). Ann. Ent. Soc. Amer. 57: 31-40. Rockel, E. G. & E. J. Hansens. 1970. Distribution of larval horse flies and deer flies (Diptera: Tabanidae) of a New Jersey salt marsh. Ann. Ent. Soc. Amer. 63: 681-84. Roth, A. R. & A. W. Lindquist. 1948. Ecological notes on the deer fly at Summer Lake, Oregon. / . Econ. Ent. 41: 473-76. Schömberg, O. 1952. Larval habitat of Tabanus sulcifrons in Oklahoma. / . Econ. Ent. 45: 747. Schwardt, H. H. 1936. Horseflies of Arkansas. Bull. Ark. Agr. Exp. Sta. 332. 66 p. Segal, B. 1936. Synopsis of the Tabanidae of New York, their biology and taxonomy. I. The genus Chrysops Meigen. J. N. Y. Ent. Soc. 44: 51-78, 125-54. Tashiro, H. & H. H. Schwardt. 1949. Biology of the major species of horse flies of central New York. J. Econ. Ent. 42: 269-72. 1953. Biological studies of horse flies in New York. J. Econ. Ent. 46: 813-22. Teskey, H. J. 1969. Larvae and pupae of some eastern North American Tabanidae (Diptera). Mem. Ent. Soc. Can. 63: 1-147. Thompson, P. H. 1970. Larval Tabanidae (Diptera) of the Great Swamp, New Jersey. Ann. Ent. Soc. Amer. 63: 343-14. 1971. Larval Tabanidae (Diptera) of the Patuxent Wildlife Research Center, Laurel, Maryland. Ann. Ent. Soc. Amer. 64: 956-57.

Downloaded from http://jme.oxfordjournals.org/ by guest on June 8, 2016

N o a t t e m p t was m a d e to estimate absolute larval p o p u l a t i o n sizes b e c a u s e d i s p e r s i o n p a t t e r n s w e r e n o t i n v e s t i g a t e d , n o r w a s t h e a m o u n t of h a b i t a t space a v a i l a b l e for o c c u p a t i o n . T h e fallacy of e s t i m a t i n g p o p u l a t i o n sizes b y e x t r a p o l a t i n g f r o m a s m a l l s a m p l e t o a l a r g e a r e a is i l l u s t r a t e d b y t h e f o l l o w i n g e x a m p l e . I n m y s t u d y a r e a , t h e d e n s i t y of C. hirsuticallus i m m a t u r e s w a s a p p r o x i m a t e l y 4 t i m e s adult t h a t of S. notatus ( T A B L E 4). H o w e v e r , t r a p p i n g d a t a s h o w e d t h a t S. notatus w a s c o n s i d e r a b l y m o r e a b u n d a n t o n a n a r e a - w i d e basis t h a n C. hirsuticallus (Anderson et al. 1974, Anderson, O l k o w s k i , H o y & L a n e , u n p u b l . d a t a ) . T h i s is b e c a u s e C. hirsuticallus a p p a r e n t l y b r e d a t 1 site w i t h i n a l i m i t e d h a b i t a t t y p e (i.e., t e m p o r a r y p o n d ) , w h e r e a s S. notatus b r e d a t n u m e r o u s sites a l o n g t h e R u s s i a n R i v e r , a far m o r e e x t e n s i v e h a b i t a t .

Vol. 12, no. 6

Lane:

1976

Wall, W. & H. Jamnback. 1957. Sampling methods used in estimating larval populations of salt marsh tabanids. J. Econ. Ent. 50: 389-91. Webb, J. L. & R. W. Wells. 1924. Horse-flies: biologies and relation to western agriculture. Bull. U.S. Dept. Agr. 1218. 36 p.

J. M e d . Ent.

691

Immature Tabanidae, density and diversity

Wilson, B. H. 1969. Tabanid larval habitats and popula­ tion densities in an alluvial area in southern Louisiana. Ann. Ent. Soc. Amer. 62: 1203-04. Wirth, W. W. & A. Stone. 1968. Aquatic Diptera, p. 372-482. In: Usinger, R. L., ed., Aquatic insects of California. Univ. Calif. Press, Berkeley & Los Angeles.

Vol. 12, no. 6: 691-694

20 February 1976

A FIELD COMPARISON OF TWO STRAINS OF STERILIZED SCREWWORM FLIES 1

1

B y £ . H . A h r e n s , H . G. H o f m a n n , J . L . G o o d e n o u g h

2

and H. D. Peterson

3

4

5

l

a

4

5

Downloaded from http://jme.oxfordjournals.org/ by guest on June 8, 2016

Abstract: Trapping studies were conducted in a Central 1963). T h e H i d a l g o C o u n t y a r e a represented Texas river valley and in South Texas rangeland during the t y p i c a l r a n g e l a n d of S o u t h T e x a s . summer of 1973 to compare dispersal and survival of a new strain ("TEX-MEX") of screwworm fly, Cochliomyia hominivorax MATERIALS A N D METHODS (Coquerel), with the standard production strain ("APHIS") used in the Southwestern Screwworm Eradication Program. T w o T E X - M E X a n d A P H I S s t r a i n fly r e l e a s e s Based on total recoveries and distances flown within the test area, the new strain outperformed the standard production strain. were m a d e on the Nueces River, while 4 were m a d e i n t h e H i d a l g o C o u n t y a r e a . T h e flies w e r e A c o n t i n u i n g o b j e c t i v e of t h e M e t h o d s D e v e l o p ­ r e l e a s e d i n u n i t s of 100,000 n e w l y e m e r g e d a d u l t s m e n t S e c t i o n a t t h e s c r e w w o r m r e a r i n g facility, p e r s t r a i n w i t h a p p r o x i m a t e l y e q u a l n u m b e r s of M i s s i o n , T e x a s is to i m p r o v e t h e q u a l i t y of t h e males a n d females. Releases w e r e m a d e every s c r e w w o r m Cochliomyia hominivorax ( C o q u e r e l ) r e ­ o t h e r w e e k . A l l flies w e r e p l a n t - r e a r e d a t M i s s i o n leased in the Southwestern S c r e w w o r m E r a d i c a t i o n u n d e r standardized rearing conditions ( G r a h a m & Program. D u d l e y 1959), a n d h a d b e e n exposed to 6700 ± 2 0 % Loss of field a d a p t a t i o n m a y o c c u r u n d e r l a b o ­ rads of g a m m a r a d i a t i o n as 5 . 5 - d a y - o l d p u p a e . ratory propagation, a n d deterioration m a y continue T h e m a j o r i t y of t h e A P H I S s t r a i n of flies w a s d e r i v e d in succeeding laboratory generations. Field per­ f r o m l a r v a e c o l l e c t e d f r o m 5 0 a n i m a l s f r o m a single f o r m a n c e c h a r a c t e r i s t i c s s u c h as r a t e of d i s p e r s a l l o c a t i o n i n W e b b C o u n t y , T e x a s i n t h e s p r i n g of f r o m r e l e a s e sites a n d d u r a t i o n of s u r v i v a l i n n a t u r e 1972. T h e T E X - M E X s t r a i n of flies w a s d e r i v e d are qualities t h a t c a n b e m e a s u r e d b y release a n d f r o m 18 c o l l e c t i o n s a t d i f f e r e n t sites i n 13 S o u t h r e c a p t u r e techniques. T r a p p i n g studies were there­ T e x a s counties a n d from 6 collections in 3 n o r t h e r n fore c o n d u c t e d i n t h e N u e c e s R i v e r V a l l e y n e a r M e x i c o states (Crystal & R a m i r e z 1975). U v a l d e , Texas a n d in Hidalgo County, Texas A l l r e l e a s e d flies w e r e m a r k e d w i t h P y l a m ® O i l f l a t i a n d i n t h e s u m m e r of 1973 t o c o m p a r e a n e w B l u e , P y l a m O i l R e d , o r D a y G l o ® fluorescent d y e s . s t r a i n of s c r e w w o r m fly ( d e s i g n a t e d " T E X - M E X " ) O n t h e 1st r e l e a s e i n t h e N u e c e s R i v e r s t u d y , 3 g developed b y t h e Agricultural R e s e a r c h Service of P y l a m O i l B l u e o r R e d d y e w a s d i s t r i b u t e d a m o n g laboratory at Mission, Texas (Crystal & R a m i r e z a p p r o x i m a t e l y 10,000 p u p a e . T h e flies b e c a m e 1975) w i t h t h e s t a n d a r d p r o d u c t i o n s t r a i n (desig­ m a r k e d on the exposed intersegmental m e m b r a n e s nated " A P H I S " ) in the A n i m a l Plant H e a l t h as t h e y e m e r g e d a n d c r a w l e d o v e r t h e d y e d p u p a e . Inspection Service E r a d i c a t i o n P r o g r a m . T h e 2 T o d e t e c t m a r k e d flies, e a c h t r a p p e d i n s e c t w a s a r e a s w e r e s e l e c t e d t o test t h e n e w s t r a i n i n 2 p l a c e d i n a n i n d i v i d u a l glass v i a l c o n t a i n i n g 1 m l different s i t u a t i o n s . of a c e t o n e . A 0 . 3 1 7 - c m s t r i p of c h r o m a t o g r a p h y T h e U v a l d e a r e a u s u a l l y h a s little r a i n f a l l i n t h e p a p e r w a s p l a c e d i n t h e 1-ml v i a l a n d left u n t i l t h e s u m m e r , r e s t r i c t i n g t h e f a v o r a b l e e n v i r o n m e n t for acetone had evaporated. I f a fly w a s m a r k e d , a screwworms to the river course (Hightower & Alley t h i n c o l o r l i n e a p p e a r e d o n t h e u p p e r m a r g i n of t h e USDA, APHIS VS, Box 969, Mission, Texas 78572, U.S.A. filter p a p e r s t r i p . USDA, ARS, Box 986, Mission, Texas 78572, U.S.A. 'USDA, ARS, Box E. C , College Station, Texas 77840, Pylam Products Co., New York, N. Y. U.S.A. Day-Glo Color Corp., Cleveland, Ohio.