Stonefly (Acroperla trivacuata)
Scientific name: Acroperla trivacuata
Common name: Stonefly
Acroperla trivacuata is a stone fly from the family Gripopterygidae. It is usually associated with stony streams, but can be found as nymphs in in permanent water drainage ditches either under water or out in vegetation.
Acroperla trivacuata original description as by Tillyard, 1923.
Dimensions: Male: Forewing, 8-5 mm. ; hindwing, 7 mm. ; expanse, 18 mm. Female: Forewing, 11mm.; hindwing, 9 mm.; expanse, 23 mm.
In this species the head, thorax, and abdomen are all brownish-black, the pronotum having a definite median longitudinal impressed line on it. The pattern of the wings is very distinctive. The ground-colour of the forewing is either fuscous or brownish, and is interrupted by three large irregular areas, arranged more or less transversely at wide intervals across the wing, these areas being very pale and subhyaline. There is also sometimes a pale area of irregular shape close to the base. The size and shape of each of the three subhyaline patches varies greatly in different specimens: sometimes they are more or less oval, with fairly regular outline; sometimes more like transverse fasciae, with irregular outline. Legs a bright medium brown. Cerci 3 mm., brownish. Appendages short, dark, slightly upcurved.
Female: Closely resembling the male, but larger; forewings more fuscous. (Abdomen shrivelled, so that ventral plate cannot be seen.).
Nymph (Described from McLellan 1998)
Generic diagnosis: Late instar nymphs slender and without projections on the pronota. Legs with pale bars basely and distally on femora and basally on tibiae. Abdominal tergites 1-10 with a medial, pale, posteriorly projecting triangle sometimes flanked by a pair of pale bars on tergites 1-9. Ocelli present; antennae and cerci less than half length of body. Early instar nymphs without hairs and pronota without flanges or spines.