1072 
MEGALOPYGIDAE. By Walter Hopp. 
apparently favouring a certain flying time. Zikan, however, observed also the of Megalopyge hyalina towards 
noon, visiting the that were kept in the breeding-box. Of many species the 9 is still unknown. 
The biology has been described of but few species, chiefly that of the North-American species. We 
have already spoken of the way the eggs are deposited. Beside three pairs of normal thoracic legs and the 
anal legs, the larvae exhibit six — instead of usually four — pairs of claspers on the abdomen ; but the first and 
last pairs of these legs (lacking the larvae of other families) on the 2nd and 7th abdominal segments are more 
feebly developed, the coronae of hooks are rudimentary here or absent. The mostly dense hair of the abdominal 
segments is grouped around a subdorsal and a dorsal pair of bristly tubercles on each segment, sometimes parted, 
from bristly to curled. Some species of Megalopyge are provided with a long hair-tuft on the neck, sometimes 
also in the centre of the dorsum. Glandular lobes the function of which is unknown hang down behind the 
spiracles of the abdominal segments. The head can be drawn into the wrinkled first thoracic segment and 
becomes quite invisible, if a huge long-haired, apically parted thoracic crest is present. The larvae of Aidos, 
however, are almost bare, the short bristles are sunk into flat hollows. Certain places on the body of some 
species exhibit, among the usual hair, shorter, thicker, hollow poisonous hairs which terminate basally into a 
poison-bag or a system of glandular tubes containing poison. The chemical nature of this poison, a colourless 
liquid, has not yet been sufficiently explored. It has a destructive effect upon the human skin, producing pain 
and a swelling of the lymphatic glands. Jones crushed a larva of Megalopyge in the hard palm of his hand; the 
effect was that his arm was paralyzed for weeks. Already when slightly touching the larva of a Pada.Ua orsi- 
lochvs with one's finger, the whole arm may be swollen for several days with fever and pain (Pohl). The latter 
larvae are colloquially known in Brazil as “bizos de fuero” (fire-animals) or as “bizos de rato” (rat-animals), 
while the Indians in Paraguay call them “Iso Yagua” (jaguar-worm); the comparison with the jaguar indicates 
at the same time the colouring, dangerousness and swiftness, for they are able to run fast, and in doing so the 
high-standing hair-tufts may have a steering effect. Some explorers are reminded of poodles by the agility 
and the rough skin of the Megalopyge-larvae-, in Mexico they are called “perrito pachon” (small hound). 
The food of the larvae is multifarious as in other low Heterocera; they were found on Cupuliferae 
(oak), Rutaceae (Citrus), Resoceae, Ulmaceae, Myrtiflorae, Papilionaceae trees, Gramineae (Panicum), and others. 
Many species, however, are not polyphagous, but rather oligophagous, because they are sometimes excellently 
adapted to the life on their food-plant. A. Schultze observed that the excrement-clods of the Megalopyge 
larvae are hollow. The pupation takes place in leathery, tenacious, dense, though not quite hard cocoons covered 
with an exterior rough and an interior smooth and dense film. In addition there is sometimes yet a third very 
loose, spongy, bulky web which strikingly copies the bark of a tree, under the cover of which the cocoons, either 
singly or by twos or threes, are flatly appressed below crotches of the trees {Megalopyge lanata). Many larvae 
remain unpupated in the cocoons for months even as long as a year and a half, dying off on being disturbed, as 
the larvae are generally very delicate and therefore difficult to breed. Empty cocoons are seen hanging on the 
trees for years after and, bleached by the sun and rain, they assume an entirely changed exterior (Zikan). The 
cocoons are provided with a roundish lid which is only superficially spun on; the way this lid is produced is 
not yet known. When the pupae, in which all the appendages of the imagines are stored in half-free cases, 
emerge, they take off part of the lid and press themselves half out of the cocoon. The species living on low plants 
embed their cocoons in the earth. The cocoons of Aidos amanda, which are spun to the underside of leaves of 
different trees, look like the webs of ichneumon-flies, especially since also their hiding places are copied. 
Most of the American species live in the hot lowlands of the tropical forests and savannas. The southern¬ 
most boundary of their range is about the line from Buenos Ayres to Mendoza in Argentina. In the north one 
species penetrates to the Atlantic States, nine to the hot Southern United States: Texas, Arizona, California. 
Six of these ten species, however, have been ascertained also in Mexico, the other four being closely allied to 
Mexican species. Megalopygidae have also been captured more than once at great altitudes in the Andes, but 
almost invariably they were such specimens that were carried from the plains up to these heights by warm 
currents of air in the evening; in the larval stage very few species occur in the cold country, in the “tierrafria" 
of the Andes. Numerous species have a very extensive range: from Mexico to South Brazil. More locally con¬ 
fined are the species of the Andes, of the savannas and pampas, representing in some respect the generalized 
species for the most part. Chile is without any Megalopygidae. 
The Megalopygidae can be divided into three divisions owing to the different course of the sub¬ 
costal vein on the male hindwing: 
I. The subcostal vein anastomoses with the whole anterior cell-vein: Trosiinae. 
II. The subcostal vein anastomoses with the basal part of the anterior cell-vein: MegaJopyginae. 
