THE BBEEZE FLY — PARASITIC BEETLE. 529 



the back. Strangely enough, the cow does not appear to feel any 

 pain from the presence of these large parasites, nor does she suf- 

 fer in condition from them, although it would seem that they 

 must keep up a continual drain upon the system. Indeed, some 

 experienced persons have thought that, instead 'of being injuri- 

 ous, they are absolutely beneficial. 



When the grub has reached its full development, it pushes it- 

 self backward out of the gall, and falls to the ground, into which 

 it burrows. Presently the skin of the pupa becomes separated 

 from that of the larva, and the latter dies, and becomes the habit- 

 ation in which the pupa lives. The head portion of the skin is 

 so formed that it flattens when dry, and can easily be pushed off, 

 like the lid of a box, permitting the perfect fly to escape. Even 

 when the insect is still in its pupal condition this lid can be re- 

 moved, so that the pupa can be seen within its curious habitation. 

 I may mention here that insects which are thus covered while in 

 their pupal state, so as to show no traces of the creature within, 

 are said to undergo a "coarctate" metamorphosis. Nearly all the 

 diptera are. examples of the coarctate insects. 



Before we close the subject of parasites, it will be needful to 

 give a brief account of one or two parasitic insects which possess 

 points of peculiar interest in the habitations which they make, or 

 in the places wherein they find their abode. 



One of these insects is a rather pretty beetle, termed Glerus al- 

 vearius. In its perfect state it is innocent enough, but in its lar- 

 val state it is so destructive among the hives, that all bee-keepers 

 will do well to destroy every Glerus that -they can catch. It is 

 generally to be found on flowers, licking up their sweet juices by 

 means of a brush-like apparatus attached to the mouth. The 

 wing-cases of most of the species are bright red, barred or spotted 

 with purple. 



The larva is of a beautiful red, and is hatched from an egg 

 placed in the cell occupied by the bee - grub. As soon as it is 

 hatched, it proceeds to feed upon the bee-^rub, and devours it. 

 Unlike many insects with similar habits, it is not content with a 

 single grub, but proceeds from cell to cell, devouring all their in- 

 habitants. "When it has eaten to the full, it conceals itself in the 

 cell, and spins a cocoon of rather small dimensions in comparison 

 with its own size. In process of time it is developed into a per- 

 fect insect, and then breaks out of its cocoon and leaves the hive, 



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