AQUATIC INSECTS IN THE ADIRONDACKS 525 



The nymph, Uke that of the preceding and that of the following 

 species (the only differences that I have observed between these I have 

 already stated in a footnote to the nymph table) has nine lateral setae, 

 and 12 mentals, of which the fifth (counting from the side) is longest; 

 the dorsal hooks on segments 4-8 are low, less considerable in length 

 than the segments which bear them, but sharp ; the lateral spines of the 

 eighth and ninth segments are less developed, and fohow in their external 

 contour the incurvate lines of the posteriorly narrowing abdomen ; the 

 lateral appendages are half as long as the inferiors, which are distinctly 

 longer then the superior. 



Sympetrum obtrusum Hagen 



Figure 30 



1867 Diplax obtrusa Hagen, Stett. ent. zeit. 28 : 95 



1893 Diplax obtrusa Calvert, Am. ent. soc. Trans. 20:264 (description and 

 figure) 



1899 Diplax obtrusa Kellioott, Odou. Ohio, p. 109 (description and figure) 



1900 Diplax obtrusa Williamson, Dragon flies Ind. p. 323 (description) 



For this and the two foregoing species I have hardly thought it worth 

 while to state the distribution in detail, it is so general throughout the 

 state, whenever any collecting has been done. 



Sympetrum albifrons Charpentier 



Figure 30 



1841 Libellula albifrons Charpentier, Lib. Europ. p. 81, pi. 11, fig. 3 

 1861 Diplax albifrons Hagen, Synopsis Neur. N. Am. p. 177 

 1900 Sympetrum albifrons Williamson, Dragon flies Ind. p. 323 (descrip- 

 tion) 



Not yet found in the state ; n5rmph unknown. 



Sympetrum corruptum Hagen 



1861 Mesothemis corrupta Hagen, Synopsis Neur. N. Am. p. 171 



1893 Diplax corrupta Calvert, Am. ent. soc. Trans. 20:264 (description) 



1897 Diplax corrupta Calvert, N. Y. ent. soc. Jour. 5:95 (listed from 



Staten Island) 

 1897 Diplax corrupta Van Duzee, N. Y. ent. soc. Jour. 5:91 (listed from' 



Lake Erie) 



1899 Diplax corrupta Kellicott, Odon. Ohio, p. Ill (description) 



1900 Diplax corrupta Williamson, Dragon flies Ind. p. 324 (description) 



This species is much more common westward; its nymph is unknown. 



