512 JounNu, oF THEAunRrclu Moseuno CoNrnol Assocrlrror.r VoL.3,No.3 SEASONAL SIZE VARIABILITY IN CULICOIDES VARIIPENNIS (DIPTERA: CERATOPOGONIDAE)IN SOUTHERN CALIFORNIA BRADLEYA. MULLENS Departmentof Entornolngy,Uniuersityof California,Riuersi.de, CA92521 Adult body size is an important consideration in assessingvector potential in blood-feeding Diptera. Nasci (1986), for example, demonstrated a significant positive relationship be- E tween body size and parity in Aedes uexans (Meigen) and Cul.exsalinarius Coquillett, and the trend was evident also for Ae. antlnnticus ' (Dyar and Knab) and Psorophora columbiae (Dyar and Knab). Within the Ceratopogonidae, adult female body size has been positively cortrend (Octoberl982-September Fig. 1. Seasonal related with fecundity in field-collected Culicoidesfurens (Poey) (Linley et al. 1970), C. 1983)in averagewing lengthsof femaleCulicoides pondin mell.eus(Coquillett) (Linley and Hinds 1976) uariipenniscollectedneara dairy wastewater (air) are mean and C. insignis Lutz (Kramer et al. 1985). Gen- RiversideCounty,CA. Temperatures precedingeach for a 10dayperiodimmediately erally, the size of adult Culicoidesis inversely values collection. related to habitat temperatures (Linley et al. 1970,Linley and Hinds 1976,Akey et al. 1978, suction traps. The study area was near a large Mullens and Rutz 1983,Kramer et al. 1985). in Chino Basin near Laboratory studies have shown that larger dairy wastewaterlagoon the are provided in Mullens adult females of C. uariipennrs (Coquillett) are Riverside,CA; details (1985).Femaleswere sorted from each collecmore fecund and survive better than smaller a single wing of each was measured individuals(Akey et al. 1978).Wirth and Jones tion, and arculus to the tip using a dissectbasal the from (1957) noted that C. uariipennisfrom cool rewith an ocular micromgions of the U.S. were larger than those from ing microscopeequipped in which wings of 25 fecollections Only eter. warm regions and also observedthat specimens here, with the reported are measured were males from the same area were larger during cooler (12 females)and De27 of October exception periods of the year. I am aware of only 2 field 2 (17 females). studies that examined seasonalsize variability cember trend in wing length was very The seasonal in detail in C. uariipennis. Zimmermanr and (Fig. 1). The Iargest females (wing distinctive Linhares2both indicated that larger females of were collectedon February 9, mm) 2.02 Iength this specieswere found in cooler periods of the (wing length 1.48 mm) were the smallest while adult flight seasonin southwesternVirginia and 7. Pooling all collections, on September collected northern California, respectively. Linhares adyearly C. uariipennis wing length was average uariipen' C. that larger demonstrated ditionally mm. The seasonaltrend in adult size (as nls were more fecund.The purposeof the pres- 1.73 by wing length) clearly was inversely indicated ent study was to document seasonalchangesin air temperature. Figure 1 indicates to related adult size of C. uariipennis in southern Califorair temperatures for the 10 day period average nia. immediately preceding each collection' as reAdults of C. uariipennis were collected at 1-3 corded at the University of California at Riverweek intervals throughout the year (October side. Temperatures of the larval habitat (mud) 1982to September1983)using small COz-baited do not necessarilycorrespondexactly to air temperatures. Adult C. uariipennis size (y) was inl Zimmerman, R. H. 1981.Seasonalabundanceand fluenced (P < 0.001) bv air temperatures(x.)' host preferenceof Culicoidesin Virginia: with empha- however, as described by the regression equafor this sis oi the ecology of Culicoi.desuariipennis (Diptera: tion, y = 2.24 - 0.026 x (r2 : 88.7Vo\, Ceratopogonidae).pl.n. dissertation, Virginia Poly- data set. This pronouncednegative regression technic Institute and State University, Blacksburg' of adult size on temperature is similar to rela188pp. of C. furens 'Linhare", A. X. 1984. The biology of Culicoides tionships observed in field studies (Linlev and Hinds (Linley C. melletts 1970), et al. uariipennis(Coquillett) (Diptera: Ceratopogonidae)in insignis (Kramer et al. 1985).The C. and 1976) of University dissertation, Ph.D. Califoinia. nortirern actual sizesof the field-collected C. variipennis BerkeleY.153 California, PP. SEPTEMBER1987 OppnltroNer, eNo Scrputrrlc NorEs 513 Kramer, W. L., E. C. Greinerand E. P. J. Gibbs.1985. Seasonal variations in population size, fecundity, and parity mtes of Culiroides insignis(Diptera: Ceratopogonidae)in Florida, USA. J. Med. Entomol. 22:163-169. Linley, J. R., H. T. Evans and F. D. S. Evans.1970.A quantitative study of autogenyin a naturally occuring population of Culicoidesfurens (Poey) (Diptera: Ceratopogonidae).J. Anim. Ecol. 39:169-183. Linley, J. R. and M. J. Hinds. 1976.Seasonalchanges in size, female fecundity and male potency in CuIicoidesmelleus (Diptera: Ceratopogonidae).J. Med. Entomol. 13:151-156. Mullens, B. A. 1985. Age-related adult activity and sugar feeding by Culicoides uariipennis (Diptera: Ceratopogonidae)in southern California, USA. J. Med. Entomol. 22:32-37. Mullens, B. A. and D, A. Rutz. 1983.Development of immature Culicoi.desuariipennis (Diptera: Ceratopogonidae) at constant laboratory temperatures. Ann. Entomol. Soc.Am. 76:747-751. REFERENCES CITED Nasci, R. S. 1986. Relationship between adult mosAkey,D. H., H. W. Potterand R. H. Jones.19?8. quito (Diptera: Culicidae) body size and parity in Effectsof rearingtemperature andlarvaldensityon fi eld populations. Environ. Entomol. 15:874-876. longevity,size, and fecundityin the biting gnat Wirth, W. W. and R. H. Jones. 195?. The North Culicoidesuariipennis.Ann. Entomol. Soc. Am. American subspecies of Culicoides uariipennis. 7l:4Il-418. USDA Tech. Bull. 1170.35 pp. in this study, relative to approximate mean temperatures,are fairly similar to those observedby Mullens and Rutz (1983) for laboratory-reared individuals of this species in New York. For example, female C. uariipennis reared at 20'C had an averagewing length of 1.79mm (Mullens and Rutz 1983),while field-collectedC.uariipennis from mid-June and late October (ca. 20"C air temperature) in the present study had average wing lengths of 1.71 and 1.69 mm, respectively. As discussedby Linley and Hinds (1976), larger adult size during cooler months likely reflects a prolonged period of larval development. This may serve to defer adult emergence during cool periods and improve the survival and reproductive capabilities of those adults that do emergeat this time.