Observation of parous rate, shedding of scales in the single white stripe on the scutum in Aedes albopictus females at a thicket in Kobe City

Abstract

Determination of the parity in mosquito involves dissecting the females under a stereomicroscope to look for parous ovaries. While dissecting Aedes albopictus females for the determination of their parity, I observed an individual wherein the scales of the single white stripe on the scutum appeared peeled off. As parous mosquitoes are more active for a longer period of the time than nulliparous mosquitoes, this increased activity in parous females could likely induce the shedding of the scales of the single white stripe. The association between parity and the shedding of the single white stripe on the scutum was examined. Ae. albopictus individuals were collected one at a time using an insect net and carefully transferred to a small plastic container. I then calculated the ratio between the length of the single white stripe and the scutum length based on the photomicrograph of the scutum. Individuals with a ratio of 0.5 or more were considered normal-type and individuals with a ratio below 0.4 as peeling-type. There was a significant difference (p<0.05) in the number of peeling-type individuals between nulliparous and parous, but the shedding of scales of the single white stripe on the scutum can’t be used as an indicator of parity in females.