Feb. '08] JOURNAL OF ECONOMIC ENTOMOLOGY 19 



underside of milk-weed leaves. The boundaries of the deformity are 

 evidently limited by the stout reticulating veins characteristic of this 

 plant. The circular ocellate gall on hard maple, known as Cecidomyia 

 ocellaris, is presumably produced in the same way, and its form is 

 governed by ordinary mechanical laws, as there are few rigid veins 

 to modify its margin. The form of irregular subcortical galls on 

 various shrubs and certain herbaceous plants appears to be determined 

 very largely by the degree of infestation, and this is presumably 

 limited by the egg-laying habits of the female. There are, in addition 

 to the gall-making species, a number of forms which may breed in 

 decaying 'wood, in other rotting vegetable matter, or subsist upon 

 fungus or even prey upon other species such as Aphids and Acarids. 



The duration of the life cycle varies greatly between the different 

 groups, and in some eases, apparently among members of the same 

 group. It is presumable that most of the Lasiopterines and the some- 

 what nearly related Rhabdophagas and their allies produce but one 

 generation annually. The same is probably true of most of the 

 Asphondylines and presumably of numerous representatives among 

 the higher groups, including such well known species as the pear 

 midge, Contarinia pyrivora, and the introduced European Contarinia 

 rumicis, which breeds in the seeds of Riimex crispus. On the other 

 hand, certain species like the Hessian fly, Mayetiola destructor 

 Say and the violet gall midge, known as Contarinia violicola, com- 

 plete the life cycle within a relatively few weeks, and the number of 

 generations is governed almost entirely by climatic conditions and 

 the presence of a supply of suitable food. A large number of our 

 species winter within their galls in the larval stage. This is true of all 

 Lasiopterines known to us which occur in subcortical galls, in stem 

 galls and in at least certain of the blister galls. It is also the case 

 with certain Hormomyias producing leaf galls on hickory. Others 

 forsake the gall and winter in subterranean cells, possibly under vege- 

 table debris and frequently in well-developed cells. 



There are some exceedingly interesting correlations existing between 

 these forms and their food habits. Among the Lasiopterines, for 

 example, the genus Clinorliyncha, represented' in this country by at 

 least one introduced European species (C millefolii Wachtl.) appears 

 to breed entirely among the florets of certain compositae such as yar- 

 row, tansy and the common daisy. Another genus, provisionally 

 referred to Baldratia Kieff., breeds in very large measure in the 

 peculiar, apparently fungous affected blister galls so abundant on 

 solidago and aster, though at least one form has been reared from 

 an apparently unaffected leaf of Erigeron. Larvse belonging to 

 Lasioptera occur largely in subcortical galls on the stems or branches 



