306 MICHIGAN SURVEY, 1908. 



rudiment on the third and regularly increasing in size backward to the 

 ninth, where somewhat surpassing the level of the tip of the 10th seg- 

 ment; they are spiuelike on segments 4-6, but somewhat laterally flat- 

 tened and distinctly decurved at the tip on segments 7-9. Lateral spines 

 on segments 7 and 8 straight and sharp, directed straight posteriorly, 

 at base very slightly angulate with the lateral margins of their seg- 

 ments, that of the 9th segment about two-thirds as long as its segment 

 and about twice as large as that of the 8th segment. The margins of 

 all the abdominal segments are hairy, especially posteriorly, and there 

 is a dense fringe across the ventral spical border of the 9th segment. 

 The superior appendage is slightly shorter than the inferiors: these are 

 triangular and sharp pointed; the laterals equal the superior in 

 length, and are stout and cylindric, and abruptly pointed. 



The larvae of the four American species of 8omatochlora now known 

 may be distinguished as follows : — 



1. Lateral setae of the labium eight: lateral spine of the 9th 

 abdominal segment more than half as long as its segment, and 

 the dorsal hook of that segment larger than its predecessors. 

 »S'. forcipata, supposition. 



Lateral setae of the labium seven : lateral spine of the 9th 

 abdominal segment less than half as long as its segment, and the 

 dorsal hook of that segment not larger, usually smaller, than some 

 of its predecessors 2. 



2. Abdomen less than one-fourth longer than wide: lateral 

 spines of the abdomen, short and broad, equilateral ti'iangles. 

 S. tenehrosa, supposition 3. 



Abdomen more than one-half longer than broad : Lateral spines 

 of the abdomen longer than more acute 



3. Dorsal hooks of the abdomen of equal size on segments 6-9. 

 Dorsal hooks largest on the 7th and 8th segments, that of the 



9th segment smaller S. linearis. 



5. Cordulia shurtleffi Scudder. This fine species is apparently com- 

 mon on Isle Eoyale, being represented by nymphs, Nos. 79 A, from Sum- 

 ner Lake (III, 5), July 29; No. 120 A. from a rock pool on beach (V, 2) 

 on August 14; and No. 126 A. from a swamp (V, II) on August 16. 



6. Celithemis eponina Hagen. Two large and four small larvae. 

 From a rock pool (Y, 2) on August 14, No. 120 A. 



7. Leucorldnia intacta Hagen. A number of larvae in bad condition, 

 apparently this species, on July 29, No. 78 A, 79 A, from the sedge zone 

 of Sumner Lake (III, 5). 



8. Enallagma sp.? A number of broken larvae: Sumner Lake (III, 

 5), July 29, Nos. 79 A and 126 A; and a rock pool on beach (V, 2) on 

 August 14, (No. 120 A) ; also from a swamp (V, 11) on August 16 

 (No. i26 A). 



Plecoptera. 



1. Arsapnia vcrnalis Newman. A number of specimens of both 

 sexes, Nos. 24, 46, and 80 (I, 1), July 6, 11, and 14. Very abundant 

 upon the cliff at the shore. 



2. Isoptrryx ci/dippa Newman. One specimen from the balsam-birch 

 forest (V, 4), on August 14 (G. 236.) 



