SOS 
General Topics. By Dr. A. Seitz. 
by a light yellow collar strikingly copying the image of the light yellow tips of the Polyporus-mushroom, 
whilst in especially arid countries, where this mushroom is rare or absent, the collar of Ccssus cossus is bark- 
grey instead of yellow. 
The more conspicuously coloured Gossidae are also rarely met with in the open air, and the small 
number of imagines found for instance of Zeuzera indica even in plantations where they 7 are destructive to 
vegetation can only be explained by the vigorous decimation of individuals during the larval stage. This is 
also verified by the very great number of relatively small eggs emitted for instance by a pubescent Zeuzera 
indica $ from its voluminous, long and stout abdomen. 
Although the Gossidae are absolutely nocturnal — many swarm even at a very late hour —, y 7 et the 
small species are easily roused and then fly 7 very swiftly also in the sunshine. All the species like to come 
to the light, also the gigantic Xyleutes (Du.omitus ) which have an expanse of up to 20 cm and whose females 
also often fly 7 to the light. The Holcocerus living in the steppes keep hiding during the day, and it is ad¬ 
visable to catch them on the lantern at night, when the imagines climb up the grass of the steppe and can 
then be more easily found. But there seem to be species the females of which do not like to come forth; 
it is at least a strange fact that not a single female specimen was to be discovered among myriads of certain 
South-American Gossidae (Hypopta ambigua Him.) covering the ground and sometimes flooding the gardens 
and streets of Argentine towns like swarms of locusts. 
The long duration of the larval stage is a peculiarity common to the Indo-Australian Gossidae as well 
as to those of other faunae, but also to nearly all the wood-boring larvae from other families. Even in the 
Tropics, where all the stages of insect life are of a much shorter duration than in the cooler climates, the 
larvae, at least those of the large Xyleutes, presumably have a feeding period of several years. If this presump¬ 
tion should prove correct, this would mean a considerably longer feeding time and a slower growth than 
that of the northern Cossus, for the Indian region — at least most of its countries — is without- the winter- 
pause interrupting the growth of the European larvae in winter. The long duration of the feeding period 
could then be explained by the easier and simpler assimilation of the food consisting of succulent herbs or 
of leaves abounding in chlorophyll, in opposition to the hard and dry wood-particles. The slowness of this 
process is proved by the relatively small excrement-balls discharged even by the gigantic larvae of Xyleutes. 
Moreover, the feeding in the wood is executed much more slowly owing to the greater resistance of the sub¬ 
stance against the bite of the larval maxillae than for instance the feeding of the larva of a Gelerio euphorbiae, 
which is able to cut out 4 to 6 bits a second from the tender petioles of Euphorbia. Thus there are two 
causes opposing an accelerated assimilation in the Cossid larvae. The real nourishment, in fact, is only the 
sap of the wood. 
Considering the systematic position of the Gossidae , all the authors agree that, as we have stated at 
other places, they would be most correctly ranged under the Microlepidoptera. The relations of the genus 
Cossus to the Tortricidae (e. g. Garpocapsa ) have been dealt with at large in Vol. II. In H atips ox's pedigree 
(Cat. Phal. 1, p. 16) they descend directly from the Zygaenidae, and in his list of families (Novit. Zool. 25) 
they are placed between the Lasiocampidae and (together with the Ratardidae and Arbelidae derived from 
them) Psychidae; M. Hering ranges them between the Aegeriidae and Tortricidae-, the latter arrangement 
presumably corresponds best to the general classification of to-day. 
The morphological and biological conditions have been largely treated upon already in Vol. II and 
XVI. Zoogeographically, we may say that the Indo-Australian fauna is without, or almost without, the 
genera containing habitually small species, such as Holcocerus, Stygia, Dyspessa, while the genera containing 
very large species, such as Xyleutes, develop a great abundance in forms especially in the southern part of 
the region. Next to this genus the Zeuzera are the best represented. While one, Z. pyrina (being absent in 
this region), is distributed over three continents — steadily gaining ground in North America —, we find in 
India and Australia more than a dozen species partly very similar to the European species, and we may 
expect a few more from New Guinea. Like the Indian Zeuzera of which multistrigata (figured also in Vol. II) 
in a certain measure continues the European form into the Indian region, there are vicariants from the 
genus Phragmataecia living in reeds in the Indian region, closely approximating the palaearctic castaneae, 
part of which exhibit the very same exterior of the European form — as for instance sumatrensis —, the 
other part being so very near to the Asiatic minor that they can be hardly separated specifically. — Thus 
nearly all the districts of the Indo-Australian fauna agree with each other as well as with the European 
fauna in the peculiar fact that beside few large grey species there lives one white, dotted species and one 
adapted to the pale colouring of reeds; only Australia and perhaps New' Guinea have more large forms. 
