Effect of cage size on Aedes albopictus wing length, survival and egg production

Aedes albopictus is currently the most widespread invasive mosquito species in the world. It has paramount medical importance since females are efficient vectors of important viruses affecting humans. The development of alternative control strategies to complement control measures has become an imperative and involves the Sterile Insect Technique (SIT). Research to improve the productivity of mass-rearing, as well as the quality of mass-reared males is of essential importance for the success of SIT.

This study compared the influence of three differently sized cages for Ae. albopictus mass-rearing on wing length, adult survival and egg production during 20 generations of colonization. Plexiglas cages of 40x40x40 cm (C1), 100 × 20 × 100 cm (C2) and 100 × 65 × 100 cm (C3) were loaded with equal adult density, and sex ratio of 1:1. An open source image processing and analysis programme (ImageJ) was used for the wing measurement and egg counting.

In all tested cages, we identified two periods separated by the generation showing the minimum value of each considered parameter (wing length, adult survival and egg production). The wing length and adult survival passed through the phases of initial decrease to about intermediate colonization time, and increased afterwards. Fecundity was steady during the first period and increased in the second one. Cage C1 demonstrated not only the best values for all parameters but also the smallest decrease in the initial phase. Recovering of the caged mosquitoes in the second half of the study was higher in cages C1 and C2, than in C3.

C1 provided the least negative selection pressure on wing length, adult survival and egg production for reared Ae. albopictus. Anyhow, since maximising mosquito density by exploiting the minimum space is a priority in mosquito mass-rearing, C2 might be a better choice for better fitting the space of mass-rearing rooms.