258 PREDACIOUS AND PARASITIC 



insecure. In some instances, it would seem, one point of attach- 

 ment does not suffice, and the egg-carrying shaft is supported upon 

 two oblique buttresses of the same material. Sometimes, perhaps, 

 the surface of the leaf is unsuitable at the point which the fly has 

 selected, and then two or four buttresses yoked together afford the 

 necessary base for the attachment of the stem, and occasionally 

 such a foundation bears two or more stems, with their attached 

 eggs. 



Dr. Fitch, in his report on Noxious and Beneficial Insects^ thus 

 describes the process of oviposition : — " Nature has furnished 

 these insects with a fluid analogous to that which spiders are pro- 

 vided with for spinning their webs, which possesses the remarkable 

 property of hardening immediately on being exposed to the air. 

 When ready to drop an egg, the female touches the surface of the 

 leaf with the end of her body, and then elevating the latter, draws 

 out a slender, thread-like cobweb, half an inch long or less, and 

 places a little oval egg at its summit. Thus, a small round 

 spot resembling mildew is formed upon the surface of the leaf, 

 from the middle of which arises a very slender, glossy, white thread, 

 which is sometimes split at its base, thus giving it a more secure 

 attachment than it would have if single." 



The interesting and beautiful nature of this arrangement, 

 which produces the effect when seen under a low magnifying 

 power of a bunch of seed pearls, each mounted upon a thread, 

 has led to the expenditure of much ingenuity in the endeavour to 

 account for so peculiar a mode of oviposition. It is the generally 

 accepted view that it has arisen from the necessity of protecting 

 the eggs against the voracity of their own kind; but I am inclined 

 to think, from my own observation, that various other insects are 

 equally likely to be the agents of destruction, especially as the 

 larva of Chrysopa perla is sufficiently strong to attack and devour 

 Aphides larger than itself three or four hours after its emergence 

 from the egg, and therefore could have little need to become an 

 egg-eater, unless in the scarcity or absence of its usual food. 



I have observed in several instances the larvae of Coccinella 

 bipunctata eat the eggs of its own kind, and the small Myifia larva 

 is known to destroy the eggs of many insects. Dr. Fitch has 

 shown in his Report on Noxious and Beneficial Insects, already 



