THE AMERICAN ENTOMOLOGIST. 



37 



duced, and, passing between the back skin of 

 the pupa and the body of the female, reacli lier 

 hinder extremity in tlie bottom of tlic pupa 

 skin. But, in addition to this extent to be pen- 

 etrated, the male has to penetrate the whole 

 length of tlie lower orifice of the follicle, 

 say half an inch, before he can reach the head 

 of the pnparinm. The femalo lays her eggs in 

 the pupariuui or pupa shell, receding: from it 

 as she docs so, and tilling the shell half or two- 

 thirds full of eggs. The rest of the shell she 

 fills with a fawn-colored down, rubbed off her 

 own body." 



1)1 order to elucidate and forever settle these 

 two points in the natural history of our Bag- 

 worm, we have closely studied the habits of 

 this insect, and have not only examined hun- 

 dreds of specimens in tlie open air, but have 

 reared great numbers within doors from the 

 egg to the perfect state, watching their opera- 

 tions day by day. The females of several in- 

 sects which inhabit similar follicles (genera 

 QSceticits Psyche, etc.), are perfectly wingless. 

 They are, indeed, the most degraded and im- 

 perfect of moths, and afford a marked excep- 

 tion to that very general, but not universal 

 rule as laid down by Agassiz, viz: that the 

 earliest condition of an animal cannot be its 

 highest. It is well known that certain Euro- 

 pean species never quit their follicles, and that 

 the shrunken body not only lies near the ori- 

 fice and i^rotects her eggs, but that it forms the 

 first food of the young larvie, who play the car- 

 nivoreus role for the first moments of their 

 lives, by subsisting on this remnant of their 

 mother's body. It is consequently stated by 

 most Enropean authors, as a characteristic of 

 the group, that the females never quit their 

 cases. But as Harris well remarked in the 

 above extract, the insect of which we now 

 write, forms an e.Kception to this rule. 



The manner in which fertilization takes place 

 is easily explained, tliougli we arc not one 

 bit surprised that (o Dr. Harris, and to all 

 who have not given close attention to the mat- 

 ter, the modus operandi should be involved in 

 such mystery. 



The males of most insects mature before the 

 females, but if wo take a given number of our 

 Bag-worm cocoons, one-half of which arc males 

 and the other half females, and cut them open 

 at the time that the first male makes his appear- 

 ance from the lot, we shall find that many of 

 the females have already burst open the pupa 

 shell at its anterior or lower end, and have 

 worked themselves through the aforementioned 

 T-shaped opening, to the lower end of the fol- 

 licle. The pupariuui is held tenaciously to the 

 upper part of the follicle by the abundance of 



soft but tough silk with which the follicle is 

 lined, but it is extenuated to nearly double its 

 natural length by the efforts which the female 

 makes in emerging. The female never with- 

 draws herself entirely from the pupa shell, but 

 holds on to it by her terminal segments, being 

 evidently assisted by the ring of wooly hair 

 already referred to. Thus, with the pupa shell 

 extended to its utmost capacity, and the addi- 

 tional length other whole body, she is enabled 

 to reach to the lower orifice of the follicle, 

 where she patiently awaits the male, and 

 after meeting him, works herself back into (he 

 pupa shell. Here she deposits her eggs in the 

 upper part, intermingling them, and crowding 

 the lower part of the puparium with the pecu- 

 liar fawn-colored down already referred to. 

 After having thus cosily secured her eggs 

 against the winter's blasts she works herself out 

 and drops exhausted to the ground. 



The eggs are very soft opaque ob-ovate bodies 

 about 0.05 inch long, and each is surrounded 

 by more or less of the down, which cannot well 

 be detached from it, and seems to be part and 

 parcel of the external surface. The fulvous or 

 fawn-colored down is in reality extruded from 

 the abdomen, and not rubbed oft' the body as 

 stated by Harris. This fact becomes apparent 

 when we consider the nakedness of the body, 

 and may be proved by dissecting an impreg- 

 nated femalo just before the laying of the eggs, 

 or by a microscopic examination of the down 

 itself. It is in reality a very fine silk and not 

 hair. Not only arc the eggs mi.ved with it, and 

 the lower third of the puparium tightly crowded 

 with it, but there is always an abundance of it 

 mixed in with the white silk at the lower end 

 of the follicle, and evidently scattered by the 

 emaciated female in her exit. 



Follicles in which the female is waiting for 

 the male may be distinguished even without 

 cutting into them, for her body entirely fills up 

 their lower third which is otherwise contracted 

 and empty. In a state of nature the females 

 scarcely ever fail to get impregnated, but in 

 confinement a majority of them thus fail, and in 

 such an event they remain at the lower part of 

 the follicle until death. Out of 82 $ follicles 

 that were set apart by us last .September, in a 

 separate cage, so that no males could reach them, 

 every one of them died in this manner, and we 

 could not find a single attempt at virginal re- 

 production, though very closely allied species 

 have been known to produce impregnated eggs 

 without fecundation. 



The males emerge during the warm morning 

 hours. They are very active, and in confine- 



