. Bulletin of the British Museum (Natural History) Entom Supp. THYRIDIDAE OF AFRICA AND ITS ISLANDS n in different species. Two anal veins are invariably present and the main variation found in the hind wings is in the relative positions of Sc + R1 and Rs. In a few species these veins join for a short part of their length, usually about half way along, but they are alway separate at the base and wing margin. In the majority of species these two veins start separately, and while they may approach closely, do not join together. The frenulum hook (retinaculum) under the fore wing is conspicuous i
. Bulletin of the British Museum (Natural History) Entom Supp. THYRIDIDAE OF AFRICA AND ITS ISLANDS n in different species. Two anal veins are invariably present and the main variation found in the hind wings is in the relative positions of Sc + R1 and Rs. In a few species these veins join for a short part of their length, usually about half way along, but they are alway separate at the base and wing margin. In the majority of species these two veins start separately, and while they may approach closely, do not join together. The frenulum hook (retinaculum) under the fore wing is conspicuous in the males as a sclerotized hook and is very prominent in some species. The hook is absent from the females. The males have a single frenulum bristle and the females usually three bristles. In only one genus (Sinecalca) is the frenulum absent in both sexes. Abdomen. The abdominal segments present fewer external characters than in some families of Lepidoptera. In some species the pattern is of use for specific determinations and in a few species the sternite of the last abdominal segment of the male is slightly modified (Text-figs 9-14), but these modifications are always slight and never approach those found in some other families, e. g. Drepanidae (Watson, 1965, Wilkinson, 1967). All species are without tympanal organs in the abdomen. Genitalia. The genitalia of both sexes show little intra-specific variation and are used to supplement the characters in the external morphology in determining the. 10 11 12 13. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original British Museum (Natural History). London : BM(NH)
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