Environmental regulation of autogeny in Culex tarsalis (Diptera: Culicidae) from Manitoba, Canada.

Temperatures less than 21 degrees C suppressed the expression of autogeny in genetically autogenous females of Culex tarsalis Coquillett from Manitoba, even under a long day photoperiod of 16:8 (L:D). Under short day lengths (8:16), the percentage of autogenous females was suppressed at temperatures from 16 to 28 degrees C; but at 32 degrees C, maximum autogenous expression occurred. When genetically similar populations were maintained at 24 degrees C and exposed to photoperiods from 14:10 to 10:14 (L:D), autogeny was suppressed from a mean of 26% progressively to 1%. When all stages were maintained at 21 degrees C, pupae were photosensitive (i.e., the percentage of autogenous females was not affected by photoperiods at which larvae were maintained). The percentage of autogenous females in field populations followed the seasonal changes in temperature and photoperiod, demonstrating environmental regulation of facultative autogeny. Autogeny appeared to be genetically stable in Cx. tarsalis. Single families from a long standing laboratory colony (greater than 60 generations) had the same range (0-80%) in percentage of autogenous females per family as did recent field-collected families from the same geographical location.