CHAP. X - Hymenoptera

Summary

Order 21. Hymenoptera. Sawflies, Ants, Bees, Wasps

Two pairs of membranous wings, venation reduced or absent; hind wings smaller than fore wings; mouth parts biting or sucking; ovipositor always present, modified for stinging, piercing or sawing; metamorphosis complete.

Three members of this order are of some importance as agricultural pests and are dealt with briefly. These three insects belong to the sub-order Symphyta (super-family Tenthredinoidea), the sawflies, and are distinguished from the remainder of the Hymenoptera by the absence of the constriction between thorax and abdomen and by the adaptation of the ovipositor for boring or sawing.

Family Tenthredinidae

Aihalia colibri F. (spinarumF.). The Turnip Sawfly

DESCRIPTION. Adult. General body colour bright orange; antennae 9-jointed, black above, yellowish beneath except at the base and apex, the joints decreasing in length but increasing in diameter towards the apex. Head and eyes black, mouth white with a whitish pubescence, three ocelli triangularly placed. Thorax with three orange marks, scutellum yellow. Abdomen in female broad, flattened with partly concealed ovipositor, sheath black at apex and hairy; in male somewhat cylindrical. Legs stout and short; tibiae hairy; tarsi whitish; apex of tibiae and joints of tarsi black. The male has the two basal joints of the antennae pale yellow, in the female the antennae are often brownish underneath. (Fig. 37.) Length 6-8 mm.

Egg. Very small, oval, whitish and semi-transparent.

Larva. On hatching, the larva is white with two black dots on the head, later the body becomes darker and the head black. When full grown the head is narrower than the second segment, shining black with a few short hairs. Each of the body segments is divided into several folds, smooth and shining without any hairs. The upper part of the spiracles is black, on each side is a longitudinal slate-coloured spot, then a row of black mostly double, oblong spots. Legs, slate-coloured, abdominal legs eight pairs, black splashed with grey, almost hidden by the overhanging folds of the body. (Cameron(2).)

Pupa. Greyish white in an oval cocoon formed of grains of earth.

LIFE HISTORY. The adults appear in May and the female deposits her eggs singly along the leaf margin on the under side, embedded in the epidermis. From two to three hundred may be laid by one female, arranged along the leaf edge at irregular intervals.