HEM AUKS ON TRICHIOSOMA LUCOUUM. lol 



year^ when I collected several, but even so early in the season I found 

 nearly all the last year's cocoons empty, the insect having taken its departure, 

 leaving its cast skin generally sticking in the hole through which it had made 

 its exit; and what is remarkable, is that the exuvia3 have been invariably left 

 with the head part in the interior of the cocoons, whilst the posterior part 

 has been drawn partly out of them; from this circumstance I was at first 

 inclined to think that the insects made their exit backwards, but such is not 

 the case. The cocoons which were thus uninhabited by the middle of March, 

 have a small irregular opening at one end, the position not being constant. 

 I am inclined to think these belong to the male fly, for reasons to be hereafter 

 stated. At present I will briefly describe the cocoons, which have all a uniform 

 appearance: they are three-quarters of an inch long, and a quarter of an 

 inch in diameter, rounded at each end, of a brown colour, and generally 

 attached the whole length to a slender twig. I have found them only upon 

 hawthorn, the bark of which they much resemble in colour, so that they are 

 not easily seen in a hedge; they are of a leathery texture, quite impervious 

 to water; and before the Fly escapes there is not the slightest hole in the 

 cocoons. Internally they are of a beautiful bronze-colour, and are of such a 

 texture as to withstand the weather for years. There certainly appears no 

 provision for a supply of air to the insect during its pupa state, or during 

 its change to a perfect fly. I should be glad if any of the readers of "The 

 Naturalist" would give me information on this point, or on any other connected 

 with this subject. The cocoon is the most perfect and secure piece of insect 

 architecture with which I am acquainted, if it can be said that one thing is 

 better than another in the works of nature, where all are equally perfect. 



I have sometimes found the bark eaten from the twig near the place of 

 attachment of the cocoon, as if the gTub had taken a feed just before entering 

 upon its long fast. Occasionally the insect is doomed never to emerge from 

 its secure dwelling, having been selected, before fabricating it, by some anxious 

 Ichneumon fly, as a fitting subject for a place of deposit for her eggs, whose 

 larvas, when hatched, cat up gradually the fabricator of the cocoon, and then 

 make their escape through small circular holes in the cocoon made by 

 themselves after they have changed into the imago state; it takes them a 

 considerable time to cut these holes, and they have to return to the work 

 very frequently before they are large enough to let them out. They try the 

 capacity of these holes often, not wishing to make them larger than is really 

 necessary, as the task of gnawing these cocoons with their little mandibles 

 is a difiicult one. I have one cocoon which has six of these small holes in 

 it, containing the remains of the victimized Saw-fly. Of the Saw-flies which 

 open the cocoons in the irregular ragged way, I know nothing, as they had 

 all taken their departure by the middle of March, when I first collected the 

 cocoons. I presume they are males, and that they make their escape about 

 a month earlier than the females. I have observed the escape of several 

 females, and I see they all cut a circular piece out of one end of the cocoon, 



