86 MARINE AND FISHERIES 



5 GEORGE v., A. 1915 



capture bears the date August 14, 1912. The earliest dates of its occurrence are 

 June 22, 1912, and June 28, 1907. 



It is most often seen hovering over patches of Sweet Gale (Myrica gale) , which 

 are common in the dryer parts of the open marshes of this region, especially near 

 the edge of the woods. 



According to my observations this species does not often stray far from its 

 breeding-grounds, as the allied species of Sympetrum frequently do. 



Strangely enough we have not found the nymph of this common species. It 

 has, however, been bred and described by Needham ('Ola). 



Leucorrhinia frigida Hagen. 



One of the most abundant and generally distributed of the marsh dragon- 

 flies of this district. Though found in all the open marshes and bays it is most 

 abundant in the sphagnum bogs on the edges of small lakes and ponds. Its 

 numbers appear to vary to some extent inversely as those of the larger dragonflies 

 with which it is commonly associated, e.g., Libellula exusta julia and Gomphus 

 spicatus. Thus it is extremely abundant in the pond on "Split Rock Island" 

 (PI. VIII, Fig. 33) where these species are absent or very rare. 



The nymphs may be dredged in large numbers from the aquatic vegetation 

 and submerged trash along the edge of this pond and are common along the mar- 

 gins of all such lakes and ponds. 



Teneral imagos were already common when the Station was opened in 1907 

 (June 16) but full-grown nymphs were still easily obtained and adults continued 

 to emerge for at least a week. In 1912 the first tenerals were observed on June 1 

 and by the 17th were very common, though a specimen emerged in the laboratory 

 as late as June 24. On August 6 this species was still fairly numerous but all the 

 individuals were old and pruinose. None were noted after this date. 



Needham's ('05) description of the nymph of L. frigida, belongs to another 

 species, probably L. hudsonica (vide infra). In a letter to the writer, he stated that 

 the species had not been reared but that tenerals of L. frigida had been found 

 at the spot where the exuvise were gathered. The nymph of frigida, unlike Need- 

 ham's species, possesses large dorsal hooks, such as are present in all the species 

 of Leucorrhinia that have been reared. 

 Nymph:— (PI. IV, Figs. 20-22). 



Very similar to that of L. intada, but somewhat smaller and the legs slightly 

 slenderer. Head similar to that of intada except in the somewhat more prominent 

 eyes. Labium of similar size and form, the lateral lobes somewhat more deeply 

 concave within, the teeth on the distal margin obsolescent, crenate, each with a 

 single spinule, lateral setse 9 or 10; mental setae 10-13, the fourth or fifth from the 

 outside longest, the inner four smaller than the others. 



Abdomen broadest at seg. 6; scarcely narrowing on 7; slightly on 8; more 

 abruptly on 9; lateral spines on 8 one-half to three-fifths fts long as the segment; 

 subparallel, those on 9 reaching about to the tips of the inferior appendages, their 

 inner margins straight and parallel. Superior appendages somewhat less elongate 



