Successful suppression of Aedes aegypti (Diptera: Culicidae) with the sterile insect technique also results in larger female mosquitoes

Sterile insect technique (SIT) is an effective method for controlling pests and has been increasing in popularity to control Aedes mosquitoes. SIT involves inundating an area with sterilized male mosquitoes to reduce egg hatch by reducing the number of fertile matings and ultimately the number of wild adults. Enacting mortality early in the larval life of Aedes mosquitoes can result in counter-productive effects due to reduced competition among developing larvae. SIT projects targeting mosquitoes have historically assessed effectiveness by monitoring egg or adult numbers, leaving out crucial information on what occurs at the larval stage. Our experiments involved collecting and hatching eggs from ovitraps in an SIT-treatment zone and 2 nearby non-SIT zones. We reared the resulting larvae in density and resource conditions similar to those in the field and compared numbers of emerging adults and sizes of emerging adult females from SIT and non-SIT zones. We hypothesize that the effectiveness of SIT in reducing adult populations is modified by density dependent mortality and density dependent growth among larvae. Our results indicate that SIT effectively suppressed the production of adult Aedes aegypti (L) in the SIT zone compared to non-SIT zones. Additionally, female Ae. aegypti, collected as eggs and reared in laboratory-simulated field conditions were significantly larger from the SIT zone than those from the non-SIT zones. Larger SIT-zone females are consistent with reduced intraspecific competition among larvae. Suppression of adult production in the SIT zone resulted in reduced predicted vectorial capacity, despite the increase in female size.