448 HABITATIONS OF INSECTS. 



ways however retaining its cylindrical form. The little 

 masses are so attached to each other in this cylinder, as 

 to leave numerous vacuities between them, which give it 

 the appearance of filagree- work. You will readily divine 

 that the excavated hole is intended for the reception of 

 an egg, but for what purpose the external tunnel is meant 

 is not so apparent. One use, and perhaps the most im- 

 portant, would seem to be to prevent the incursions of 

 the artful Ichneumons, Chrysidce, &c. which are ever on 

 the watch to insinuate their parasitic young into the nests 

 of other insects : it may render their access to the nest 

 more difficult ; they may dread to enter into so long and 

 dark a defile. I have seen, however, more than once a 

 Chrysis come out of these tunnels. That its use is only 

 temporary, is plain from the circumstance that the insect 

 employs the whole fabric, when its egg is laid and store 

 of food procured, in filling up the remaining vacuity of 

 the hole ; taking down the pellets, which are very con- 

 veniently at hand, and placing them in it until the en- 

 trance is filled a . — Latreille informs us, that a nearly 

 similar tunnel, but composed of grains of earth, is built 

 at the entrance of its cell by a bee of his family of 

 pioneer s h . 



Under this head, too, may be most conveniently ar- 

 ranged the very singular habitations of the larvae of the 

 Lhmaean genus Cynips, the gall-fly, though they can 

 with no propriety be said to be constructed by the mo- 

 ther, who, provided with an instrument as potent as an 

 enchanter's wand, has but to pierce the site of the foun- 

 dation, and commodious apartments, as if by magic, 

 a Reaum. vi. 251-7. t. xxvi. /. 1. b Latr. Fourmis, 419, 



