178 THE CANADIAN ENTOMOLOGIST 



That such a large, conspicuous insect as Cordulegaster could 

 have escaped my observation all these years, if it has been here 

 continuously, seems at first sight improbable, and yet in this case 

 I am inclined to believe, from the numbers of nymphs present in 

 the creek, that the species is a regular resident. The adults of 

 Cordulegaster are short-lived and their season of flight is probably 

 over soon after the usual time of my arrival at Lake Simcoe in 

 late June or early July, and my visits to their haunts, which have 

 not been frequent, have probably all been too late. 



In conclusion we may summarize the following points, which 

 are suggested by the foregoing observations. — 



1. Certain species of dragonflies are much more abundant 

 in certain localities during warm seasons than during cold seasons. 



2. This abundance is probably not due to the emergence of 

 large numbers of individuals from their breeding-places, but to 

 the greater activity of flight in warm weather, whereby the insects 

 are dispersed to "localities not visited in cooler seasons. 



3. The Odonate fauna of a restricted locality contains a 

 large percentage of transient resident species and stragglers from 

 other localities, such species varying greatly from year to year. 



THE NORTH AMERICAN SPECIES OF HABROCYTUS 

 (CHALCID-FLIES). 



BY A. A. GIRAULT, GLENNDALE, MD. 



Generic Characters of Hahrocytus. 



The scutellum bears a more or less distinct cross-carina (or 

 indicated as such) before apex (except in medicaginis and horrowi). 

 The spiracular sulcus is present, foveate (exceptions noted). The 

 clypeus is finely striate. The genus differs from Pteromalus 

 mainly in mandibular structure but the abdomen is less flat, longer 

 (conical) and the neck of the propodeum not usually conspicuous, 

 but short and variable between the species. The propodeal 

 spiracles are long and elliptical (smaller in canadensis). The types 

 of all the species have been seen. The following table is based 

 on the females: 



May, 1917 



