ECOLOGY OF ISLE ROYALE. 305 



NEUROPTEROID INSECTS FROM ISLE ROYALE, MICHIGAN. 



DE. JAMES G. NEEDHAM^ CORNELL UNIVERSITY. 



A small but interesting collection of aquatic larvae of dragonflies, 

 stoneflies and mayflies was obtained from Isle Royale, and the fine 

 stonefly, Pteronarcys dorsata Say, from the Northern Peninsula. Among 

 the dragonfly larvae were two that are hitherto undescribed, a species 

 of Sympetrum too immature for description, and the cast skins and the 

 young larva of a species of Somatochlora, described below. The list is 

 as follows: 



Odonata. 



1. Anaoo Junius Drury. A young larva from Isle Royale was col- 

 lected on August 14 (No. 120 A) in a rock pool on the beach (V, 2) ; 

 and another on July 29 at Summer Lake (III, 5). 



2. AescTvna sp.? perhaps constricta Say. Represented by both cast 

 skins and nymphs from Sumner Lake (III, 5), Nos. 170, 221, 72 A, 

 77 A, 78 A, 79 A; a rock pool on the beach (V, 2) on August 14; in the 

 stomach of a duckling loon {Gavia imher) from Slskowit Lake (V, 6) 

 August 10, No. 108 A; and from the margin of a swamp (V, 11) 

 on August 16 (No. 126 A). 



3. Aeschna sp? A second species, represented by a single young 

 larva, was taken in a rock pool (V, 2) on August 14 (No. 120 A). It 

 has lateral spines on segments 5-9 of the abdomen, that of 5 (usually 

 absent) being very small. 



4. SomOrtochlora sp? Perhaps S. foreipata Selys. (This suggestion 

 as to the species is based solely on the fact that this species is known 

 to occur commonly at Duluth, Minn.). A single young nymph in 

 alcohol, July 26, from the head of Eock Harbor, No. 162; and a cast 

 skin (No. 89) from Rock Harbor (III, 1) July 14, 1905. Being new to 

 science, a description drawn from the cast skin is here-^ath ofl'ered. 



Length 23 mm., abdomen 13 mm., hind femur 7 mm., width of head 6 

 mm., of abdomen 7 mm. 



Body stout, hairy on all margins. Antennae very hairy, and also the 

 legs, especially the tibiae externally. Head with a ruflf of stiflf rough 

 recurved hairs overspreading the abruptly narrowed hind angles. La- 

 bium stout and wide, its hinge reaching posteriorly well between the 

 bases of the fore legs. Median lobe prominently angulate in the mid- 

 dle; mental setae about thirteen each side, the outermost eight of these 

 in a close-set uniform series; some of the smaller inner ones more or 

 less out of line. Lateral setae eight ; hook small, hardly longer than the 

 setae, but much stouter; teeth crenulately recurved and densely spinu- 

 lose margined. 



The wing cases reach posteriorly to the tip of the 6th abdominal seg- 

 ment. Dorsal hooks on abdominal segments 3-9, beginning with a mere 

 40 



