THE CANADIAN ENTOMOLOGIST. 97 



certain as to the parentage of the curious eggs. Yet the newly hatched 

 larva which he described differed from the mature larva in lacking the 

 ventral branchiae, resembling in this respect the mature form of another 

 aquatic larva of an allied genus ( ' Chanliodes), and as some leading ento- 

 mologists believed that the eggs described by Mr. Riley might belong to 

 this last genus, further evidence as to the real nature of said eggs was 

 desirable. The paper presents this evidence and confirms the previous 

 determination. The Cory dolus larva is traced through its stages of growth 

 and then compared with that of Chauliodes. Several interesting scientific 

 facts are brought out. The larva undergoes about six moults. The 

 double nature of the thoracic tracheae in Corydalus appears in the first 

 larval stage, and the branchial nature of the lateral filaments is proved by 

 the tracheae leading to their tips. The ventral branchiae first appear in the 

 second stage (after first moult) and from three main stems each with 

 bifurcate or trifurcate filaments. The branching filaments become more 

 and more numerous and complex with each moult. The tracheae also 

 lead more and more strongly to these ventral branchiae and less strongly 

 to the lateral ones, with age. The stigmata are obsolete in the first three 

 stages and in the fourth are only clearly distinguishable on the four or five 

 larger abdominal joints, being still obsolete on the terminal ones. 



The motion of the larva is invariably backwards. When newly 

 hatched it moves actively about in the water by sudden sweeps of the 

 abdomen beneath, very much as a lobster is known to do; and even when 

 full grown a somewhat similar motion is employed in swimming. In the 

 water a constant motion of the ventral branchial tufts is kept up, the main 

 stem being first moved quickly backward and upward so as to bring the 

 whole tuft close to the body, the filaments of which it is composed being 

 then closely appressed to each other. The main stem, is then brought 

 more slowly down in the opposite direction, when the filaments spread 

 and enlarge the whole to its utmost. In pure water the motion occurs 

 about once a second ; as the water becomes impure the motion becomes 

 more rapid, and the larva issues from the water as soon as possible, being 

 able to live out of water for several days even when only a few months 

 old. Well developed ova are found even in the larva when only two- 

 thirds grown. 



The paper gives detailed comparative descriptions of the Corydalus 

 and the Chauliodes larvae. This last may always be distinguished from 

 the former by having a smooth and unarmed skin ; that of Corydalus has 



