EVIDENCE OF AN EMBRYONIC DIAPAUSE IN A TROPICAL PHANEROPTERINAE (INSECTA ENSIFERA TETTIGONIOIDEA)

Eggs of Stictophaula armata Ingrisch 1994 from Chiang Mai, Thailand (1 8 degrees 47'N, 98 degrees 55'E), were incubated at 25 degrees C in th e laboratory. Under constantly humid conditions, favourable for develo pment, about half of the eggs hatched within 60 days after oviposition (peak 20-36 days), the other half hatched between 120 and 350 days af ter oviposition, mostly between 180-260 days. In the late hatching egg s, embryonic development ceased temporarily at mesentrepses. Eggs laid by females that themselves had hatched from early or from late hatchi ng eggs gave similar results. When newly laid eggs were incubated at 6 0% RH, no hatching occurred, but if the eggs were first incubated fora period varying between 2 and 12 months at 60% RH and then allowed to absorb water, hatching occurred with a unimodal distribution between 2 3 and 72 days after moistening of the eggs (peak 24-40 days). Hatching success was not reduced by a desiccation period of up to 6 months. Th e results are interpreted as the occurrence of an egg diapause that is eliminated by the incidence of drought.