THE STATE ENTOMOLOGIST. 157 



might be explained in a more natural way. The term is justly applied 

 to those actions which are prompted by exterior influences or pecu- 

 liarity of organization, and which are performed unconsciously; but 

 by its too general application, most people have acquired a deep-set 

 idea that all animals act under its power, and have nothing akin to 

 our reason ; whereas there is hardly anything more certain than that 

 true reason of degree exists very generally in the animal kingdom; 

 or that what we know as pure instinct may have been developed by 

 natural law, i. <?., first acquired by experience and afterwards fixed as 

 a habit by heredity. 



The subtle influences of the late fall which seem to convey 

 through every pulse of nature, intelligence of the approaching win- 

 ter, and which cause all animals to prepare for their hyperborean 

 sleep, no doubt originally induced the young larva of the ancestral 

 type from which our Disippus and the other species of the genus 

 sprung, to prepare for itself some shelter. The gradually increasing 

 cold and the decrease of nourishment in the leaf, would act as physi- 

 cal prompters, and the pitcher-like house, which at first strikes us as 

 so remarkable, is the simplest structure that could be made with the 

 materials at command. The characteristic smoothness of its food- 

 plant — forbidding as it does the shelter under loose bark which many 

 larvre seek — would also tend to develop such a trait. That this trait 

 — this instinct — should only be developed under similar conditions to 

 those which gave birth to it, is not so remarkable ; and that it does 

 only so develop, seems certain, for I have every reason to believe 

 that while the insect is two-brooded further north, it is sometimes 

 three-brooded with us, and consequently that this peculiar instinct 

 obtains either in the second or third generation; according to circum- 

 stances. 



ITS PARASITES. 



Though not generally known to entomologists, our Disippus 

 butterfly is very subject to the attacks of parasites, at least three 

 distinct species infesting it in the preparatory states. One of these 

 is a Tachina-fLy, of which I have often noticed the eggs fastened 

 transversely on the back of the neck of the larva, but of which I 

 have not obtained the fly. In all probability it does not destroy the 

 larva till the latter is nearly full grown. The other two I will briefly 

 describe as no mention has heretofore been made of them. 



The Disippus Egg-parasite.— The eggs already described were 



_^ [Fig. 72.] very abundant last fall on a certain clump 



f * "i-fH$=3 i; ^j^ /'of willows near Kirkwood, and of about 



\, ,--." ' L-—-" \5^€j/ two hundred obtained, fully one-half of 



> ^vf /jk/C\ ^ uem were parasitised. Instead of hatch - 



^^^7W/777^ /r f/f $%> v n £ 0U ^ i n t° l ar vse, as they would have 



' j** [ih}y;' A '\ done if they had been unmolested, these 



^^^ Jk %' 1\M .^last produced little dark colored four- 



e^v w a. ^*IjP winged flies, from four to six of which 



