View Image Gallery of Tribe Arctornithini n.

The definitive feature of this new tribe is the signum of the female genitalia, which is a large, uniformly but not densely scobinate plate (e.g. Figs 380-383).

The forewings are deeper, more triangular than in average members of the other tribes. The venation is variable, with an areole present or absent on the forewing. The discal mark when present, is a single dot, chevron or lunule. The ground colour is usually pale, and scaling can be generally sparse, or reduced in translucent patches.

In the male genitalia, the uncus is usually short, broadly based. The aedeagus is also relatively very short, and the saccus is small, shallow or absent. The valves are simple, primitively undivided, but may have a harpe arising from a saccular pocket.

The biology of the tribe is distinguished by the fact that the eggs are laid singly and the larvae are solitary (T.R.D. Bell, MS). The adult female lacks the characteristic scale tuft at the apex of the abdomen with which members of other tribes cover their egg-masses. The pupa tends to be green, exposed, suspended by its cremaster (cylindrical, with hooklets bunched at the apex) in a loose cradle of silks within which it rotates when disturbed (Bell, MS). In this, the tribe resembles the Leucomini.

The larvae are typical of the family but often have the hairs over each extremity much longer and directed forward anteriorly and backward posteriorly. Gardner (1938) distinguished the larvae of two species that would now be included in the type genus from other lymantriids by the presence of a pair of dorsal tufts or pencils on the metathorax and, on the abdomen, well separated and equally small supraspiracular and postspiracular verrucae. The subspiracular and supraventral abdominal verrucae are close, at the same level, rather than well separate, one above the other as in Nygmiini and Orgyiini. They are close also in Lymantria but more unequal and set somewhat obliquely.

The tribe has by far its greatest richness in the Oriental tropics, particularly in Sundaland. Several species have been reared from Dipterocarpaceae, and a general adaptation for feeding on this plant family might be one explanation for
the high diversity in Sundaland. The plant family has fewer lepidopteran defoliators generally than might be expected from the predominance of its foliage in some south-east Asian forests (Holloway, 1989b).

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