The Journal of Heredity 67:71-78. 1976.

Palp-antenna, a Homeotic Mutant in Aedes aegypti J. L. PETERSEN, J. R. LARSEN, AND G. B. CRAIG, JR.

T PRESENT, three homeotic mutants have been reported in mosquitoes. In Aedes albopictus, a L. mutant, proboscipedia, has been described in which the labella of the proboscis is modified into tarsi3'23. In Aedes aegypti, a similar mutant, also called proboscipedia, has been reported by J. R. Roberts, Jr. of Georgia Southern College, Statesboro, Georgia 30458 (personal communication). Also inAedes aegypti, the mutant intersex has certain homeotic manifestations causing duplication of male genitalia13. The term homeosis was coined by William Bateson2 to describe mutations in which one member of a homologous series shows characteristics typical of another structure in that series. The present investigation is a study of the genetics and morphology of a fourth homeotic mutant in mosquitoes, palp-antenna, found in Aedes aegypti. Mosquitoes homozygous for the palp-antenna gene (ppa) have a variable number of antenna-like segments extending from the apex of the maxillary palps. The characteristic sexual dimorphism of both the palps and the antennae is evident in the mutant. Since penetrance is complete, fitness is high, and the mutant is easily detected, palpantenna is a useful genetic marker.

International Reference Centre for Aedes at Notre Dame. Mosquitoes were maintained by procedures outlined by Craig and VandeHey12. Mosquitoes were reared in an insectary where the temperature was maintained at 27° ± I°C and the relative humidity was 80 ± 10 percent. Photoperiod was 18 hours light and 6 hours dark. Larvae were fed a suspension of liver powder (Nutritional Biochemicals Corp.). Adults were provided with apple slices. Females were blood-fed on narcotized white mice. The scanning electron micrographs were taken at the University of Illinois at Urbana-Champaign employing a Kent-Cambridge Stereoscan Electron Microscope. Two methods of specimen dehydration were used. Recently-emerged adults were etherized and then preserved by the acetone vapor treatment described by Truman25. This method prevents shrivelling that occurs during air drying. Alternatively, adult mosquitoes were dehydrated in an alcohol series and then the alcohol was gradually replaced by Freon in an alcohol-Freon series. Material in 100 percent Freon was then dried by the critical point method ". Dehydrated mosquitoes were then mounted on stubs and coated with carbon followed by gold-paladium in a ratio of two to one. The mode of inheritance and linkage relationships of the palp-antenna gene were determined by both F2 Materials and Methods data and backcrosses. In Aedes aegypti, sex is The mutant, palp-antenna, was discovered in 1971 by determined by a single gene (m) or by a small block of one of us (GBC) among the progeny of a laboratory chromosome that functions as a gene l5. Females are the colony of Aedes aegypti that originated in Kenya. The homogametic sex (mlm) and males are heterogametic mosquitoes were originally collected from a domestic (Mlm). Therefore sex can be used as a genetic marker. water jar in the village of Shauri Moyo, Rabai Dis- In addition to sex, the following genetic markers were trict, near Mombasa, Kenya by W. Hausermann of the used: linkage group I markers—rust-eye (/•«)", redMosquito Biology Unit of the International Centre of eye (re)lb, and white-eye (u')4i5; linkage group II markers Insect Physiology and Ecology. —Silver-mesonotum (Si)l3 and spot-abdomen (5-)l2; 12 All the strains and marker stocks mentioned in this linkage group III marker—black-tarsi (bit) . study are maintained at the World Health Organization

A

Results The authors are, respectively, doctoral candidate at the University of Notre Dame; professor of entomology and head of the Department of Entomology, University of Illinois, Urbana, Illinois 61801; and professor of biology and director of the Vector Biology Laboratory, University of Notre Dame, Notre Dame, Indiana 46556. Joint contribution from the Vector Biology Laboratory, University of Notre Dame, and the Department of Entomology, University of Illinois. This investigation was supported by NIH training grant no. A1-00400, NIH research grant no. AI-02753 and AFOSR grant no. 71-2065. The technical assistance of Mary Fisher, University of Illinois, with the SEM work is gratefully acknowledged. Please address reprint requests to Dr. Craig.

71

Morphology The maxillary palps of wild-type female Aedes aegypti are five-segmented. The first two segments are about as long as they are wide; the third segment is about three times as long as wide; and the fourth segment is the longest, being about four times as long as wide. The fifth is a tiny globular segment that fits partially into a depression at the apex of the fourth segment; it is often obscured by scales projecting beyond the distal end of segment four and is not easily observed. Female

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The Journal of Heredity

FIGURE 2—Scanning electron micrograph of the head and palps of mosquitoes. A—wild-type female; B—wild-type male;

C—palp-antenna female; D—palp-antenna is approximately 6 0 x .

male. Magnification

maxillary palps extend approximately one-fifth the length of proboscis (Figures 1 and 2). The maxillary palps of wild-type maAe Aedes aegypti are also five-segmented. Segments one and two are very short; the third segment is longer than all the others combined; the fourth and fifth segments are similar in length. Male maxillary palps curve slightly outward away from the distal end of the proboscis. When straightened, the total length of the male palps is slightly greater than that of the proboscis (Figures 1 and 2). The fine structure of the maxillary palps includes the same morphological features in both sexes, although numbers and distribution may differ. Structures found on the palps of mosquitoes are: scales, microtrichia, sensilla chaetica, and sensilla basiconica (thin-walled pegs)18'20. In palp-antenna mutants the female palps lack the fifth globular segment and have a variable number of antennalike segments extending from the distal end of the fourth segment. The number of antenna-like segments varies from one to six or more. The net effect of the mutation is that the female palps are extended to as much as onethird the length of the proboscis (Figure 2). Male palpantenna mutants lack both the third and fourth palpal

segments. These are replaced by a variable number of antenna-like segments, usually three or four. The net effect on the male is to shorten the palps, since the total length of the antenna-like segments is shorter than the combined length of third and fourth segments (Figure 2). The antenna in both sexes consists of a ring-like basal segment, the scape, a spherical second segment, the pedicel, and a long flagellum of 13 segments9. The scape and the pedicel are not apparent on the mutant palps. Only flagellar segments have been observed extending from the palps. The flagellar segments of wild-type female antennae are composed of a narrow, basal, sclerotized ring followed by a clear membranous section and then by a sclerotized cylindrical section that forms the largest portion of the segment10-24 (Figure 1). A whorl of six large sensilla chaetica arises from the base of each of the flagellar segments except the first19. The sensilla chaetica have fluted shafts with sturdy sockets that are provided with what Mclver 19 had called "lateral cuticular keels." Numerous small sensilla trichoidea are distributed over the surface of the cylindrical portion of the segment10

Petersen et al.: Palp-antenna Mutant

FIGURE 3—Micrograph of details of mutant and wild-type males. A —detail of mutant palp showing sensilla chaetica (940x); B—wild-type male antenna showing whorls of sensilla chaetica

73

(300 X); C—mutant palps showing scales on antenna-like segments (210x).

(Figure 1). The flagellar segments of the male antennae wild-type antennal flagellar segments to the degree seen are spindle-shaped. Numerous large sensilla chaetica are in the female mutant. In the mutant male these segments arranged in two crescent-shaped whorls projecting from are longer than in the wild type and the sensilla chaetica the sides of each segment19 (Figure 3). The sexual are not arranged in regular crescent-shape whorls. In dimorphism of the antennae is evident in the mutant addition, scales may be present on all mutant segments, (Figures 1 and 3). whereas scales are limited to the first flagellar segment of Palp-antenna mutants show the fine structure of the the wild type (Figure 3). antennae described above. * Mutant females usually In both the male and female mutant the sensilla possess distinct antenna-like flagellar segments (Figure I). chaetica tend to remain recumbent along the shaft of the These flagellar segments show whorls of fluted sensilla flagellar segments. Wild-type adults have the same appearchaetica firmly set in keeled sockets. Sensilla trichoidea ance at the time of emergence from the pupa, but within are present on the cylindrical portion of the segment. 24-48 hours post-emergence the sensilla chaetica are The mutant flagellar segments differ from the wild-type fully extended from the shaft10. antenna flagellar segments in several characteristics. Mutant antenna-like segments may be distorted and Scales may be present on more than just the first present a lumpy, distorted appearance (Figure 1). Howflagellar segment of the mutant. Scales are found only ever, even on these teratoid segments fluted sensilla on the first flagellar segment of wild-type antennae. The chaetica with characteristic keeled sockets, basiconic number of sensilla chaetica in the basal whorl may pegs and trichoid sensilla can be readily distinguished. differ from six. Sensilla chaetica may even be distributed among the sensilla trichoidea on the cylindrical portion of the segment. Basiconic pegs, limited to the fourth Mode of inheritance palpal segment of the wild type, may be present on the When palp-antenna individuals are outcrossed to wildmutant flagellar segments (Figure 1). type individuals, the F, progeny are all wild type. Palp-antenna males show characteristic clumps of long When these F, are backcrossed to palp-antenna indisensilla chaetica. However, the segments extending from viduals the backcross progeny show 1: 1 segregation of the distal end of palpal segment three do not resemble mutant to wild type. Of 1924 backcross progeny scored,

The Journal of Heredity

74

978 were wild type and 946 were palp-antenna. On the hypothesis of 1: 1 segregation, the x 2 statistic = 0.532, which is not significant (0.5 > P > 0.1). When the F, were crossed among themselves and the F2 were scored, the ratio of wild type to mutant was not significantly different from 3 : 1 . Among 1735 F2 progeny scored, 1332 were wild type and 403 were mutant. On the hypothesis of 3: 1 segregation, the x 2 statistic = 2.91, which is not significant (0.1 >P > 0.05). Based on the above evidence it is concluded that the palp-antenna phenotype is inherited as a single recessive gene with complete penetrance. The name of the gene locus is here designated palp-antenna and is assigned the symbol ppa. Inheritance of this mutant is associated with sex. When palp-antenna females were crossed with wild-type males, the F, were all wild type. The distribution of the backcross progeny when F, males were backcrossed to homozygous females is given in Table 1. The ratio of mutant to wild type does not differ significantly from 1 : l;x 2 = 0.848(0.1 > P > 0.05). However, the sex ratio does differ significantly from 1: 1 in favor of the males; x 2 = 28.14 (f 0.97). Thus, Silver and palp-antenna assort independently. Table II summarizes the evidence for sex linkage ppa m + M only based on F2 progeny. In the cross x +m ppa in ppa M , . palp-antenna males, , can be detected as a recomppa in binant class. The other recombinant classes cannot be distinguished from non-crossover classes. However, these palp-antenna males make up half the possible recombinant males. Therefore, this number can be doubled to obtain an estimate of the crossover frequency6: (2 x ppa males) Frequency of crossover = x 100. total males

Distribution of progeny Palp-antenna

x

The following-phenotypes were scored in the F2 progeny: Expected Observed

Table I. Palp-antenna: mode of inheritance*

Wild type

+ in Si

The same reasoning holds true for the cross

* P: palp-antenna 9 x wild type 6 F,: all wild type Backcross: palp-antenna 9 x F, 6

ppa m

ppa M

+m

+ in

Table II. Recombination between palp-antenna and sex, based on F, progeny from reciprocal crosses F 2 progeny Genotype of P class

99

Genotype of F,0.05

28.36

75

Petersen et al.: Palp-antenna Mutant where palp-antenna females are the only apparent recombinant class. The crossover frequencies based on F, data were 25.94 and 28.36, respectively. Linkage relationships based on backcrosses In order to determine the map location, the mutant was outcrossed to other sex-linked markers, the progeny were sib-mated and multiple marker stocks involving palp-antenna were constructed. The mutants rust-eye (ru), red-eye (re) and white-eye (w) were most suitable for this purpose. The following homozygous marker ppa re , ppa w stocks were constructed: ppa ru and ppa ru

ppa re

ppa w

In order to determine the linkage relationships of these genes the homozygous stocks were outcrossed to a standard laboratory wild-type stock. The Rockefeller Institute strain (abbreviated ROCK) was used for this purpose. Heterozygous males were backcrossed to the homozygous recessive female. Since males are heterogametic (Mini) and females are homogametic (mini), the sex locus could be used as a genetic marker for linkage studies. In effect, these were all trihybrid crosses. The results are summarized in Tables III and IV. The best estimate of the crossover frequency between any two loci is the pooled total of the appropriate recombinant classes divided by the corresponding total number of progeny. By this procedure the best estimate of the distance between ppa and m is 27.86 crossover units. The 95 percent confidence limits for this estimate, assuming a binomial distribution of crossover frequencies, are L, = 25 and L2 = 30.5 for n = 1000. This is a conservative estimate since the actual sample size is 6487. These limits were obtained from a table in Pearson and Hartley22 providing binomial confidence limits. The crossover frequencies of all the backcrosses can be conveniently summarized by a linkage map (Figure 4).

palps varies from one to six or more. In some cases there is only an amorphous mass of tissue at the tips of the palps provided with several sensilla chaetica. Under the pressure of selection and two generations of brothersister matings, a strain was established with fairly uniform expressivity. These individuals all showed 3-4 antennalike segments. The enhanced expressivity in the selected strain facilitated scoring in crosses. Biological parameters Several biological characteristics were examined in order to determine the fitness of the mutant phenotype. The fitness of the palp-antenna phenotype was compared to that of the ROCK strain. Percent hatch was determined for both palp-antenna and ROCK strains. Eggs of individual females were collected from single pair cages and held for 4 days at

Table IV.

Crosst

Ninety-five percent confidence limits for crossover probability estimates by region* Crossover region

P

u

L2

1.32 26.60 27.92 16.11 4.18 20.29 18.75 3.85 22.60 28.74 12.83 41.57 26.76 15.15 41.91

0.8 24.0 25.4 14.0 3.2 18.0 16.6 2.8 20.0 26.2 11.0 38.3 24.1 13.1 38.8

2.0 29.7 31.0 18.9 5.8 23.2 21.5 5.0 25.4 32.0 15.1 44.8 29.8 18.0 45.1

Expressivity

A A A B B B C C C D D D E E E

The phenotypic expression of palp-antenna is variable. The number of antenna-like segments extending from the

* Read from a table in Pearson and Hartley 22 using n = 1000 t Crosses as given in Table III

Table III.

Score of

Cross 9

6

ppa-w

Summary of backcross data progeny %CO region 2

%CO 1 &2

1.32

26.60

27.92

2055

16.11

4.18

20.29

5

1323

18.75

3.85

22.60

179

37

1684

28.74

12.83

41.57

185

50

1551

26.76

15.15

41.91

% CO region 1

SCO ,

SCO 2

DCO

2350

37

859

6

3252

1644

325

80

6

ppa re M + + m

1029

243

46

+ M + ppa m w

1021

447

ppa M w + m +

951

365

ppa ru m ppa ru m

„ ++ M

B

ppa re m ppa re m

„ + + M

C

ppa re m ppa re m

D

ppa m w ppa m w

E

ppa m w ppa m w

ppa ru m ppa re m

v

m-w

NCO

A

v

ppa-ru ni-tn ppa-m ppa-re re-tn ppa-m ppa re re-m ppa-m ppa-m m-w ppa-w ppa-m

The Journal of Heredity

76 ppa

ru

w

re

••

13-18 16-19 26-29

38-45 FIGURE 4—Estimated map of linkage group I in Aedes aegypti. Numbers indicate approximate linkage distances.

27°C and 80 percent relative humidity. The eggs were counted before hatching in deoxygenated water. The results were 92.45 ± 1.39 percent hatch for palp-antenna and 90.62 ± 1.55 percent for the ROCK strain. No significant larval or pupal mortality was associated with the palp-antenna phenotype. The host preference of palp-antenna mosquitoes was determined by means of a wide-tunnel type olfactometer. Two mice were presented on one side and a hand was inserted into the apparatus on the other. The mosquitoes responding to either side enter a plexiglass cylinder, but are prevented from landing on the host by a wire screen. Thus, attraction, not feeding preference, is measured. Both palp-antenna and ROCK strains were tested. One hundred females were tested at a time, and the results are presented in Table V. There was no significant difference between the responses of palp-antenna and the ROCK strain. Both strains were anthropophilic, i.e., man-preferring. Discussion The segments of wild-type female antennae and palps have large numbers of sensory hairs in the following categories: sensilla chaetica, small sensilla trichoidea distributed over the surface of the segment, and sensilla basiconica. These sensillae have been shown24 to be innervated by anywhere from 3 to 5 nerve fibers. Their general morphology (presence of a socket etc.) indicate that they are chemosensory type receptors. As has been noted, these receptors are located on both the mutant and wild types. It is not known at this time whether or not these sensory receptors in the mutant forms continue to be innervated by the same number of nerve fibers, or if they would be capable of the same kind of sensory input as in the wild type. In the mutant forms there is a definite altering of the distribution of the sensilla chaetica, trichoidea, and basiconica on the palps and antennae. However, the basic external morphology

of the individual sensory receptors is not altered significantly from those found on the wild type. The total number of sensilla differ from the wild type with fewer numbers on the mutant. There should be an extensive study with the transmission electron microscope to determine if there is any change in the innervation of the individual sensory receptors, i.e., sensilla trichoidea, chaetica, and basiconica. These types of sensory receptors have been shown21 to be capable to responding to sugars and salts by recording excitation of the nerve fibers located within the receptor. While the mutational changes as described are quite apparent, it is not known whether there are significant changes in the number of nerve fibers or whether they have lost their ability to respond as chemoreceptors. Since palp-antenna is sex-linked, significant deviations from 1: 1 in the sex ratio affect the recovery of the palp-antenna mutant. It is not unusual for the sex ratio of Aedes aegypti to be in the range of 40-45 percent female. When sample size is large, i.e., greater than 400, and the observed sex ratio is 45 percent, the probability is less than 0.05 that the observed deviations from 1:1 are due to sampling error alone. As sample size increases beyond 400 the deviations become more significant if the sex ratio remains 45 percent female. Thus, when sample size is large, sex ratio distortions

Table V. Host preference of palp-antenna compared with ROCK based on response in an olfactometer. The figures refer to the number responding out of 100 5 5 tested Palp-antenna

ROCK (wild type) 2 mice

hand

total

2 mice

hand

total

1 5

70 76

71 81

0 16

71 75

71 91

Petersen et al.: Palp-antenna Mutant

77

account for most of the deviation of observed recovery tion) was able to demonstrate interference across the of the mutant from the expected value. centromere of linkage group I in Aedes aegypti. A multiple-marker stock including palp-antenna and The map distance between palp-antenna and sex was estimated to be between 20-23 crossover units based on white-eye has been synthesized to take advantage of the data from the ppa-re stock. The ppa-w and ppa-ru fact that these loci mark the distal ends of linkage stocks each gave estimates in the range 26-29 crossover group I. Other markers included in the stock are Silverunits. Such heterogeneity in crossover frequency in- mesonotum and spot-abdomen in linkage group II and volving the re locus has been discussed by Bhalla and black-tarsi in linkage group III. This combination of Craig7 and McClelland15. Bhalla and Craig7 report markers is especially useful for determining linkage group values ranging from 1.0 to 7.8 for the region re-m. relationships of unmapped mutants. McClelland l5 reported values ranging from 4.8 ± 0.9 to 16.0 ± 2.1 for the same region. The age of the heterozySummary gous parent in the backcrosses may account for some of this heterogeneity, but it does not explain the differences Palp-antenna is a homeotic mutant of Aedes aegypti observed between the various marker stocks. It is that modifies the apex of the maxillary palps of both possible that there are inversions present in the re sexes into a variable number of antenna-like segments. stocks, but this has never been demonstrated cytologi- The fine structure of the antenna, including sexual cally even after an extensive survey of some laboratory dimorphism, is apparent in the mutant palps. Palpstrains including RED 1 . antenna is a sex-linked recessive. A linkage distance The ppa locus is farther from the sex locus than any of 27.9 ± 0.45 crossover units from sex is estimated from other sex-linked gene. Mapping the palp-antenna locus F2 and backcross data. Penetrance is complete; exhas lengthened the known chromosome 1 linkage pressivity is variable. The fitness of the mutant compares map. The other genes on the ppa side of sex are the favorably with that of the wild type. The mapping of the eye-color mutants, red-eye and rust-eye. The most ppa locus lengthens the known chromosome 1 linkage distal gene on the other arm of chromosome 1 is white- map of Aedes aegypti. eye. White-eye is epistatic to both red-eye and rust-eye. When a mosquito is homozygous for w neither the red Literature Cited nor the rust phenotype can be expressed. This fact severely limited the simultaneous use of markers at the 1. ASMAN, M. Cytogenetic and developmental effects of extreme ends of chromosome 1. The existance of the gamma radiation on Aedes aegypti (L.). Ph.D. Thesis, Univ. palp-antenna locus eliminates this problem. The palp- Notre Dame. 112 pp 1966. 2. BATESON, W. Materials for Study of Variation. University antenna white-eye stock can be used when it is necessary Press, Cambridge. 1894. to follow both arms of chromosome 1. 3. BAT-MIRIAM, M. and G.B. CRAIG, Jr. Mutants in Aedes The sex locus is known to be closely linked to the albopicttts (Diptera: Culicidae). Mosq. News 26:13-22. 1966. centromere of chromosome 1 in Aedes aegypti15. There4. BHALLA, S.C. White-eye, a new sex-linked mutant of fore, palp-antenna is on one arm of the chromosome Aedes aegypti. Mosq. News 28:380-385. 1968. while white-eye is on the other. This arrangement of 5. and G.B. CRAIG, JR. White-eye, a new sexthe markers makes the palp-antenna white-eye stock linked mutant inAedesaegypti. (Abstr.)Bull. Entomol. Soc.Am. ideally suited for determining chromosome behavior 11:171. 1965. 6. and . Bronze, a female-sterile mutant of and frequency of crossing over in both arms simultaneously. The palp-antenna white-eye stock was used Aedes aegypti. J. Med. Entomol. 4:467-476. 1967. and . Linkage analysis of chromosome I of by Ved Brat and Rai26 to determine which arm of 7. aegypti. Can.J. Genet. Cytol. 12:425-435. 1970. chromosome I was involved in a radiation-induced re- Aedes 8. CAMPBELL, R.C. Statistics for Biologists. 2nd ed. ciprocal translocation. In addition, the effect of the Cambridge University Press, Cambridge. 1974. translocation on the frequency of crossing over in linkage 9. CHRISTOPHERS, S.R. Aedes aegypti (L.)The Yellow Fever group I could be measured. Translocation heterozygotes Mosquito. Its Life History, Bionomics and Structure. Camshowed almost a 50 percent increase in crossover fre- bridge University Press, Cambridge. 1960. quency between ppa and M. The recombination fre10. CLEMENTS, A.N. The Physiology of Mosquitoes. The quency betweenppa and A/ was 34.55 percent in the trans- Macmillan Co., New York. 1963. 11. COHEN, A.L., D.P. MARLOW, and G.E. GARNER. location heterozygotes compared to 23.71 percent in the standard, nontranslocated control. Crossing over was A rapid critical point method using fluorocarbons ("Freons") suppressed in the interstitial segment of the translocated as intermediate and transitional fluids. J. Microscopie 7: 1968. arm, marked by the loci M and w. The observed cross- 331-342. 12. CRAIG, G.B., JR. and R.C. VANDEHEY. Genetic over frequency was 6.00 percent compared to 14.49 variability in Aedes aegypti (Diptera: Culicidae). I. Mutations percent in the standard control. affecting color pattern. Ann. Entomol. Soc.Am. 55:47-58. 1962. 13. and W.A. HICKEY. Genetics of Aedes aegypti. In The palp-antenna white-eye stock has also been used to determine if a crossover in one arm of chromosome 1 Genetics of Insect Vectors of Disease. Chapter 3. J. Wright has any effect on the probability of a crossover in the and R. Pal, Eds. Elsevier Publishing Co., Amsterdam. 1967. 14. DUNN, M.A. and G.B. CRAIG, JR. Small-antenna, a sexother arm. If a crossover in one arm increases the linked mutant of Aedes aegypti. J. Hered. 59:131-140. 1968. probability of a crossover in the other arm, this is called 15. MCCLELLAND, G.A.H. Sex-linkage at two loci affecting coincidence; a decrease is called interference. By com- eye pigment in the mosquito/I edes aegypti (Diptera:Culicidae). paring the observed number of double crossovers with Can. J. Genet. Cytol. 8:192-198. 1966. the expected number, Ved Brat (personal communica16. MCDONALD, P.T. and K.S. RAI. Correlation of linkage

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The Journal of Heredity

groups with chromosomes in the mosquito, Aedes aegypti. Genetics 66:475-485. 1970. 17. MCIVER, S.B. Comparative study of antennal sense organs of female culicine mosquitoes. Can. Entomol. 102: 1258-1267. 1970. 18. . Comparative studies on the sense organs on the antennae and maxillary palps of selected male culicine mosquitoes. Can. J. Zool. 49(2):235-239. 1971. 19. . Fine structure of the sensilla chaetica on the antennae of Aedes aegypti (Diptera: Culicidae). Ann. Entomol. Soc.Am. 65:1390-1397. 1972. 20. and C. CHARLTON. Studies on the sense organs on the palps of selected culicine mosquitoes. Can. J. Zool. 48:293-295. 1970. 21. OWEN, W.B. The contact chemoreceptor organs of the

mosquito and their function in feeding behavior. J. Insect Physiol. 9:73-87. 1963. 22. PEARSON, E.S. and H.D. HARTLEY. Biometrika Tables

for Statisticians. Vol. I. Cambridge Univ. Press. 1958. 23. QUINN, T.C. and G.B. CRAIG, JR. Phenogenetics of the

homeotic mutant proboscipedia in Aedes albopictus. J. Hered. 62:3-12. 1971. 24. SLIFER, E.H. and S.S. SEKHON. The fine structure of

the sense organs on the antennal fiagellum of the yellow-fever mosquito Aedes aegypti (L.). J. Morph. 111:49-67. 1962. 25. TRUMAN, J.W. Acetone treatment for preservation of adult and larval mosquitoes. Ann. Entomol. Soc. Am. 61: 779-780. 1968. 26. VED BRAT, S. and K.S. RAI. An analysis of chiasma frequencies in Aedes aegypti. Nucleus 14:184-193. 1973.

Reprint Collections Sought Most geneticists maintain collections of reprints. After a lifetime of active research, a geneticist is likely to have amassed a bulky collection, most of which a younger geneticist would find outdated. Thus many such collections are eventually just thrown away. As a historian of genetics and evolution, I have found from 10 years of experience that a substantial reprint collection is essential for efficient research. Therefore I am trying to put together an excellent reprint collection for the years 1900 to the present. This collection will of course be open to all interested scholars. A major problem is locating reprint collections that are available for donation or purchase. Any help that readers can offer will be greatly appreciated. Please direct correspondence to: William B. Provine Assoc. Prof. History of Biology Department of History Cornell University Ithaca, New York 14853

Palp-antenna, a homeotic mutant in Aedes aegypti.

Palp-antenna is a homeotic mutant of Aedes aegypti that modifies the apex of the maxillary palps of both sexes into a variable number of antenna-like ...
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