Feeding Ability of Micronecta grisea Nymphal Instars and Adults on Third Instar Aedes aegypti Larvae

Abstract

Pygmy waterboatmen, Micronecta grisea, were collected and used to establish laboratory cultures in order to study the predation rates and feeding behavior of nymphal instars (N) and adults upon third instar larvae (L3) of Aedes aegypti to assess their potential for biological control. The body length, head capsule size and head length of 330 nymphs and 71 adults of M. grisea, collected from Nonthaburi Province, Thailand, were measured using a stereo microscope. In contrast to head capsule size and head length, which yielded overlapping size distributions, five discrete nymphal instars (N1 – N5) plus adults could be classified by body length; the 1st (N1; 0.54 – 0.65 mm), 2nd (N2; 0.69 – 0.84 mm), 3rd (N3; 0.9 – 1.11 mm), 4th (N4; 1.29 – 1.56 mm) and 5th (N5; 1.74 – 1.98 mm) nymphal instars plus adults (2.07 – 2.43 mm). Using body length to define developmental stadia, nymphs were classified as three discrete size categories, small (N1 & N2), medium (N3 & N4) and large (N5), and together with adults these four clases were examined for predation rates and prey handling times when fed L3 Ae. aegypti at different predator to prey ratios. Prey searching and handling times decreased with increasing M. grisea size (developmental stadia), and were consistent with a Type II functional predator-prey response.