The Life Cycle of Perlesta placida (Plecoptera: Perlidae) in an Intermittent Stream in Northern Texas1

Abstract

Perlesta placida (Hagen) emerged when x daily stream temperatures approached 20°C. Adults came to lights May-July, with maximum attraction at 0.5-1.0 h after sunset. Mean head capsule width decreased seasonally from 1.4 to 1.3 mm in males and 1.8 to 1.6 mm in females. Laboratory life span was ca. 8 days. Fecundity ranged 130-453 eggs/♀ with x = 276±96 eggs. Eggs were smooth, brown, measured 0.44×0.28 mm and underwent a differential 5-6 mo or one yr and 5-6 mo diapause. Diapause was broken when x daily stream temperatures decreased to ca. 18 °C in Oct.-Nov. Eyespots appeared in Sept., ca. 4 wks before hatching. First instars were unpigmented, had 4 cereal and 9 antennal segments and their x interocular distance was 0.16 mm. The life cycle was a fast type with greatest growth beginning in Mar., after emergence ofHydroperla crosbyi (Needham and Claassen). Female larvae were consistently larger than males. Size frequency distribution indicated ca. 12-16 instars. The 1st few instars fed primarily on detritus, whereas older carnivorous larvae preferred Chironomidae larvae; other food items included Simuliidae, Choroterpes mexicanus Allen and Hydropsyche simulans Ross.