362 Transactions of the Canadian Institute [vol. ix 



Feeding habits as in the preceding order. 



Order Diptera. 



Fam. Cecidomyidae. 

 Fam. Trypetidae. 



Concerning the feeding habits of this order, Packard^^ states that 

 the Cecidomyia larvae must absorb their nourishment through the skin 

 or suck it in at the mouth. He bases his conclusion on the facts that the 

 larvae are devoid of jaws and that excrement is not found in the mature 

 galls. 



Walsh** from the same data has come to the conclusion that the 

 larvae abrade the interior of the galls with the chitinous structure, the 

 so-called breast bone, on the ventral surfaces of their bodies. The 

 irritation produces a flow of liquid from the cells and upon this the larvae 

 feed. He further states that the mouth of the larva of Eurosta solidaginis 

 Fitch possesses a horny, black termination that probably serves the 

 same purpose of abrasion as the breast bone of the Cecidomyidae. 



Both of these observers have concluded that the nourishment is 

 obtained by the larvae without the destruction of the cell walls, and 

 that these do not form a part of the food of the larvae. My observations 

 confirm this view. In several species such as Lasioptera corni Felt and 

 Cecidomyia ocellaris O.S. (Figs. 33, 40), the walls of the cells, through 

 which the larvae were obtaining food, were apparently uninjured. In 

 other forms as Cecidomyia triticoides Walsh (Fig. 37), and Cecidomyia 

 pellex OS., the cells of the nutritive zone had collapsed as the contents 

 were withdrawn. 



Order Hymenoptera. 

 Fam. Tenthredinidae. 



By the time the larvae in this family are full fed, nothing remains of 

 the galls but a thin rind on the outside of each. Both the cell walls and 

 contents are swallowed indiscriminately. 



Fam. Cynipidae. 



In this family the larvae are invariably surrounded by a layer of 

 thin-walled cells which usually present a radial elongation especially in 

 the innermost rows (Fig. 58). The cells of this nutritive zone contain 

 sugar, starch, oil emulsion and albumen. The amount of starch varies 

 directly and the sugar inversely with the distance of the cells from the 

 larvae. 



With regard to the manner in which this zone is used as food by the 

 larva at least two views are current. The following statement of Kerner" 

 may be presented as an adequate expression of one of these theories: 

 "The larva when hatched finds the inner wall of the chamber which has 

 been fitted for its temporary abode always provided with the necessary 



