Effect of relative humidity on emergence and on dispersal and regrouping of first instar Nezara viridula (L.) (Hemiptera: Pentatomidae).

Laboratory studies with 1st instar of southern green stink bug, Nezara viridula (L.)ldicated that relative humidity (RH) greatly affected nymph emergence and survivorship up to the 2 nd instar, reaching the maximum value (~ 90%) with RH of> 80%. At 60% RH, 60% of the nymphs energed and survived, while with 0% RH only ~ .15% of eggs hatched, and most nymphs died. Emerged nymphs from egg masses placed in plastic boxes with a gradient of humidity remained on egg shells for ca. one day. After this period, they dispersed and regrouped on top of shells 6.8+- :0.67 times, until they abandoned the shells toward the source of humidity, avoiding the water-saturated areas. Duration taken for each rearrangement (dispersal + regroup) increased with time, with a range of ~ 26 min to 44 min. The mean duration of the grouping behavior on egg shells after each rearrangement decreased from ~ 102 min (1 st) to 24 min (6th and last grouping). The rearrangement behavior of 1 st instars on top of egg shells apparently compensates for the water loss of nymphs