ODONATA OF THE VICINITY OF GO HOME BAY 83 



SESSIONAL PAPER No. 39b 



search was made for nymphs but without success at this spot. A number of Tetra- 

 goneuria nymphs, however, were taken from beneath stones along the shore of a 

 channel and two of these yielded female imagoes of T. spinigera, emerging on June 

 2. The other nymphs proved to be T. cynosura simulans. Thus, although the 

 nymphs of these two species may be associated with each other we are inclined to 

 the opinion that T. spinigera is most at home in somewhat marshier stations than 

 those preferred by its congener. 



A careful comparison was made between the exuvisB of these two species but 

 no differences could be detected between them except that in spinigera the lateral 

 abdominal appendages average slightly longer than those of cynosura. The differ- 

 ence, however, does not appear to be constant. Prof. Needham, who referred certain 

 nymphs to this species by supposition, employed as differential characters the length 

 and amount of divergence of the lateral spines of seg. 9. The two species discussed 

 here are quite alike in respect to these features, which vary considerably among 

 individuals of the same species. 



The adult life of this insect appears to be rather short, July 4 (1907) being the 

 latest date upon which it has been observed. 



Tetragoneuria cynosura simulans Muttkowsky. 



Syn. T. semiaquea (Burm.) Auctt. 



In 1907 this species was exceedingly abundant. Tenerals were just beginning 

 to appear on our arrival at the Station and by June 25 their numbers had about 

 reached their height. Specimens were taken until July 22. In 1912 they were 

 much less numerous and though common were not abundant. Mature nymphs 

 were collected on May 29th, the first imago emerging on June 13, and four others 

 on the following day. The latest date of emergence that we have recorded is June 

 19th and the last day on which we observed an adult is July 31. The single in- 

 dividual seen on this day was a female and was taken with a female of Hagenius 

 brevistylus which was feeding upon it. 



The nymphs of this insect are very common in sheltered bays and channels 

 where there is a certain quantity of marsh vegetation but where the water is not 

 stagnant. The small marshy coves which are very common along the rocky shores 

 everywhere in this district seem to be the favorite haunts of this species. On the 

 slender reeds which grow in such situations the exuvisB may be very numerous 

 during the season of emergence. 



I have seen half a dozen or more exuviae on a single reed. They also frequently 

 transform on boathouses. Full-grown nymphs are quite often taken from the 

 undersides of stones close to the shore. 



This species is most abundant about June 25. It flies everywhere on land, 

 but is most common about the shore in sheltered places or in sunny openings 

 in the woods. On a small, somewhat bare island just outside the outer coast 

 we found it on June 25th, 1907, almost in swarms. They were flying about in 

 the sunshine apparently quite aimlessly and seemed not to be feeding. 

 396—6^ II 



