AQUATIC INSECTS IN THE ADIRONDACKS 527 



Nymph. Total length 21 mm; abdomen 12 mm ; hind femur 6 mm ; 

 width of head 6 mm, of abdomen 7.5 mm. 



Easily recognizable among other libelluline nymphs (when well grown 

 at least) by the head twice as wide as long, the entire absence of dorsal 

 hooks, the smooth and depressed body, and by the superior appendage 

 being one third shorter than the inferiors and twice as long as the 

 laterals. The labium is large, and the median lobe is at its maximum 

 size; hook long and slender; laterals 10; mentals about 12, the fifth or 

 sixth (counting from the side) longest; the lateral spines of the eighth 

 and ninth segments of the abdomen are very similar in size and shape, 

 those of the ninth segment extending posteriorly almost to the level of 

 the tips of the inferior appendages. 



MESOTHEMIS 



There is a single species occurring within the state. 

 Mesothemis simplicicoUis Say 



1839 Libel 1 ul a simpliGieollis Say, Acad. nat. sci. Phil. Jour, 8:28 

 1861 Mesoth em i s siiaplicicollis Hagen, Synopsis Neur. N. Am. p, 170 

 1893 Mesothemis simplicicoUis Calvert, Am. cDt. soc. Trans. 20:265 



(description) 

 1895-97 Mesothemis simplicicoUis Calvert, N. Y. ent. soc. Jour. 3:48 



and 5 : 94 (listed from New York, Westchester co., Ithaca and To- 



wanda creek) 



1899 Mesothemis simplicicoUis, Kellicott, Odon. Ohio, p. 113 (descrip- 



tion) 



1900 Mesothemis simplicicoUis, Williamson, Dragon flies Ind. p. 325 



This is another species of wide distribution, that is much more common 

 southward and westward : a single specimen was seen at Saranac Inn. 

 I remember having seen but very few at Ithaca. I bred this species and 

 P. longipennis in Illinois in 1895. The images of this species have 

 more of the gomphine habit of squatting on the ground than any other 

 libellulines known to me. That may be the meaning of the long spines 

 on the hind femora. They do not seek the topmost twigs of reeds, as do 

 most other shore-frequenting species, but settle by preference in some 

 bare path, or aslant a board at the edge of the water. The nymphs are 

 rapid cHmbers among reed stems. In hfe their eyes are yellowish exter- 

 nally, and the teeth on the edges of the labial lobes are white. The 

 bodies of the nymphs are greenish with little pattern showing. 



Nymph. Measures 'in total length 17 mm; abdomen 9 mm; hind 

 femur 5 mm ; width of head 5 mm, of abdomen 5.5 mm. 



It is recognizable at a glance among all other libelluline nymphs known 

 to me by the thickness of the body, the bulging prominence of the eyes, 

 the relative brevity of the abdomen, and the decurved appendages at the 

 apex of the abdomen. 



