526 BRITSIH LEPIDOPTERA. 



The natural history of the Malacosomas is exceedingly interesting. 

 The eggs are laid closely upon each other round and round a twig in a 

 very close spiral, with the micropylar ends free, i.e., those opposite the 

 apparent point of attachment to the twig (vide, antea, p. 435), the 

 whole embedded in a thick liquid gum. The batch of eggs thus forms 

 a sort of necklet, which can readily be slipped off the twig when it 

 contracts on drying. Concerning the source of this gum (in M. 

 neustria), Keaumur writes (Mem., ii., p. 97) : " J'en ai ouvert pour 

 voir si je trouverois dans leur corps le reservoir de cette gomme brune 

 qu'elles employent en si grande quantite ; je n'ai pu la meconnoitre, 

 je l'ai trouvee dans cette vessie double, ou plutot ces deux vessies que 

 nous avons dit avoir communication avec l'anus. Ces reservoirs sont 

 bien plus grands dans notre papillon, que dans d'autres papillons qui 

 le surpassent considerablement en grandeur. Avant qu'il ait commence 

 a faire ses ceufs, ces reservoirs sont remplis d'une matiere trop epaisse 

 pour que le nom de liqueur lui convienne, elle a la consistance d'une 

 bouillie — et sa couleur est tres-brune ; en un mot, il est visible que 

 ces vessies sont remplies de la gomme fondue dont le nid doit etre 

 construit, de celle dans laquelle les oeufs doivent etre enchasses. 

 L'usage de ces vessies bienconnu, nous apprendque les vessies sembla- 

 blement placees qu' on trouve a tant d'autres papillons, fournissent la 

 liqueur qui humecte leurs oeufs lorsqu'ils sont pres de sortir, et qui 

 les attache contre les corps sur lesquels ils sont deposes. Mais la 

 quantite de la liqueur contenue dans ces reservoirs ne doit pas 

 etre sensible, lorsqu'il n'en faut fournir que pour humecter legere- 

 ment les oeufs." The larvae live gregariously and form large silken 

 nests on the branches of various plants, a habit that has given rise to 

 the popular American name of • " tent " caterpillars for these larvas, 

 although the North American species, disstria, erosa, and thoracica are 

 said to be tentless. Dyar divides (Can. Ent., xxv., p. 37) the larvse of 

 the North American species of this genus into two groups : (1) The 

 species whose larvae do not spin a nest — M. disstria, M. erosa, M. 

 thoracica. (2) Those that do spin a nest — including all the remaining 

 species. The larvas of the first group rest in companies on the trunk 

 without covering, those of the second, with the possible exceptions of 

 M. constricta and M. incurva, are all nest-spinning, their webs being 

 formed in the forks of the smaller branches or twigs. The " Eastern 

 region," from the eastern slope of the Kockies to the Atlantic, has two 

 species, one belonging to each group, viz., disstria and americana. The 

 " Pacific north-west," from the Cascade Mountains to the Pacific, has 

 also two, one to each group, viz., erosa and jiluvialis, but the latter, 

 which takes the place of americana, is not its representative, as erosa 

 is of disstria. The " Central arid region " has but one species, unless 

 incurva, described from Arizona, be found throughout the range of 

 fragilis. M. fragilis is the only species not a tree-feeder, and this 

 habit has evidently been induced by the absence of deciduous trees in 

 its habitat. California has five endemic species, unless it be that 

 thoracica is the same as erosa of Oregon. Kivers' description of the 

 former recalls the latter most vividly, but he makes no mention of the 

 broad subdorsal blue band so distinct in the larva of erosa. Grote says 

 (Ent. Rec, vi., p. 112) that, as species are now understood, it is 

 clearly an impossibility, to consider some of the American Malaco- 

 somas distinct species, since the names can only be applied with 



