MEGALOPYGIDAE. By Walter Hopp. 
1071 
16. Family: Megalopygidae. 
Like many other lepidopteral families, the Megalopygidae are distinguished by a great number of charact¬ 
eristics. We cannot conclude any affinities from single ones of these characteristics, as the species of to-day 
do not show, which of these characters are due to acquired convergency. In morphological respect, the Megalo¬ 
pygidae are nearest to the African Phaudinae which Handlirsch regards as a tribe of the Zygaeninae, these 
as a subfamily of the Zygaenidae, and the latter like the Megalopygidae as a family of the superfamily of Zy- 
gaenina. However, a closer relationship of the Megalopygidae to the Zygaenidae is not proved. Cf. Jordan in 
Nov. Zook 34 (1928) p. 135 on the morphological differences between the Megalopygidae and Phaudinae. 
The only fact is that the American Megalopygidae of our days represent, in a sexual-morphological re¬ 
spect, almost uninterrupted stages of development, among which also the palaearctic, Mediterranean-African 
genus Somahrachys can be so cogently ranged that it may be said to be a constituent disjoined from the American 
Megalopygidae. The other parts of the world are without any Megalopygidae at all, and thus they can be justly 
denoted as an old typical element of the neotropical fauna, having sent only very few branches, of highly deve¬ 
loped species to the nearctic region. 
Ancient authors as well as collectors of the present days have frequently confounded the family with 
Lymantriidae, Lasiocampidae, Zygaenidae, Cossidae, Limacodidae. For this reason it is absolutely necessary to 
describe them rather minutely. 
The neuration is characterized in the forewing by the presence of the analis, in the hindwing by three 
— instead of two — separate inner-margiual veins, and in both wings by the presence of a cellular media divid¬ 
ing the cell as far as the base or almost to it in two longitudinal parts. The cell is relatively extensive in both 
wings; therefore the veins arising from it appear to be shorter than for instance in the Lasiocampidae, so that 
they are easily distinguished already by this characteristic. The media is never forked within the cell of the 
forewing in the American species; and there are no accessory cells. The axillaris of the forewing is very shortly 
forked at the base and frequently, though not invariably, despatches one or several secondary branches to the 
inner margin. The palpi are very small, they may even be mere knobs or absent. The tibial end-spurs are 
likewise small, individually from all stages of atrophy and coalescence to entire absence; no middle spurs of 
the tibiae, no second pair of tibial end-spurs or tarsal end-spurs. The fact that the atrophies of the palpi 
and spurs are due to correlation becomes evident in the Aidinae, where they are somewhat more distinctly 
developed. The proboscis is also very rudimentary or absent, and there is no tympanal organ. However there 
is between the eye and the antenna, laterally sunk into a hollow, Jordan’s chaetosema, a circular organ of 
sense with radially placed bristles. The antennae are differently developed in the $ and $• The male antennae 
are pinnate, though only basally in the Aidinae, flattened and plain in the Zyzypyge\ the length of the stem 
and the width of the pinnae vary much individually in some species. The female antennae are more narrowly 
pinnate or even plain, sometimes they also vary individually. The frenulum is normally developed, capable 
of function in the except in Megalopyge which genus lacks the retinaculum. The thorax of the Megalopygidae 
exhibits a remarkable characteristic of the family: the deep longitudinal median fold in the anterior part of 
the mesonotum. The abdominal segments are densely haired and clothed with parallel short bristles of a some¬ 
times bright (orange) colour. The $ exhibits a bundle of externally smooth anal wool which is once or twice 
sharply curled inside, from which the family derives its name; this silky wool is the felt covering the eggs which 
are mostly flatly deposited in paired rows. 
Most of the species are very hairy and have rather broad wings with rounder inner margins; the wings 
are never indented, tailed, very much prolonged, or pointed. The largest species has an expanse of 90 mm, 
the smallest of 10 mm. Megalopygidae have almost only been captured at night on artificial lights, many species 
