THE CANADIAN ENTOMOLOGIST. 367 



THE IMMATURE STAGES OF THE TENTHREDINOIDEA. 



BY ALEX. D. MACGILLIVRAY, 



LTniversity of Illinois, Urbana, Illinois. 



An interest in the study of the adults of the Tenthredinoidea 

 has emphasized the necessity for some knowledge of their imma- 

 ture stages. This opportunity came the past summer through the 

 offer of the Maine Agricultural Experiment Station to spend some 

 time there collecting, breeding, and studying the larvae of this 

 group. 



It is essential in all phylogenetic studies that the most 

 generalized forms should, be identified and the lines of specializa- 

 tion from these forms determined. This identification has been 

 made for the adults and it was hoped that a study of their larvai 

 would throw some light on the validity of this classification. 



The eggs are laid by the female wathin the tissue of the host 

 plant. Where the larvae are borers, the eggs are laid in holes made 

 in the stems of shrubs or in the hard wood of the limbs or trunks of 

 trees, wuth a thread-like ovipositor. Where the larvae are leaf 

 feeders, the eggs are placed in slits made by the female from the 

 under surface, with an ovipositor consisting of two plate-like 

 structures. The number of eggs placed in a single leaf varies greatly 

 among the different species. In some only a single egg is inserted 

 in a leaf; in others a large number, varying from three or four to 

 thirty or forty. The recently laid eggs are difficult to locate, but 

 they become swollen with age and then their location is easily 

 determined. 



The method of placing her eggs adopted by the female de- 

 termines, to a certain extent, the feeding habits of the larvae, as to 

 whether they are solitary or gregarious feeders. Many species are 

 solitary feeders throughout their entire life, a single larva on a leaf, 

 part of a bush, or entire bush; the others are gregarious 

 through the placing of many eggs in a single leaf or on closely ad- 

 jacent leaves. Where many eggs are laid in a single leaf, the 

 larvae developed from these eggs may be gregarious throughout 

 their entire larval life or only for a time, when they are half grown 

 they gradually disperse over <l\\ parts of the bush and are solitary 

 in their habits for the remainder of their life. 



November, 1913 



