16 Annals Entomological Society of America [Vol. XV, 



The paraprocts are generally well developed, chitinized and 

 fused with the bases of the cerci, although in the nymphs of 

 some forms and also the adults of others they may be more 

 distinctly separated. Frequently they bear copulatory append- 

 ages in the form of hooks, as in Isoperla sp. (PI. II, Fig. 18), or 

 of long processes which fit together into a spout-like organ 

 (Dictyopterygella, teste Klapalek, '12). Crampton's figure of 

 Acro7ieuria brevipennis shows a pair of small hooks on the 

 paraprocts in addition to the larger ones borne by the supra- 

 anal plate. 



Owing to lack of material I have been unable to study 

 satisfactorily the penis of the Plecoptera. When present it is 

 usually single, but according to Crampton, the bipartite form 

 occurs in some forms, such as NemouracompletaWalk. (1. c, 

 PI. II, Fig. 16). In this figure processes resembling parameres 

 are represented. In some cases it is membranous and eversible, 

 in others it is partly chitinized, and it may be provided with a 

 .virga, as in Perlesta flavida (Crampton, 1. c, PI. II, Fig. 14). In 

 Perla tristis Hag. it is a large, stout structure of simple rounded 

 form, with a rather large terminal aperture, (PI. II, Figs. 19, 20). 

 The distal part of the ejaculatory duct has longitudinally 

 folded walls and is darker than the rest of the organ. There are 

 no parameres nor other chitinous parts. 



Embiidina. 



The only species, males of which I have studied, is the 

 widely distributed Oligotoma saundersii Westw., but the 

 numerous figures in Enderlein's monograph of the order (Ender- 

 lein, '12) afford a basis for a more general survey of the genitalia 

 of this group. 



The most primitive form is undoubtedly the large South 

 American ClotJioda nohilis Gerst., which is remarkable for the 

 symmetry of the terminal abdominal structures, and for the 

 lack of the various copulatory processes, so strikingly developed 

 in all the other genera. In most of the Embiids there is a 

 shortening of the ninth abdominal tergum and an enlargement 

 of the tenth, somewhat suggestive of the Dermaptera. In 

 Clothoda the tenth tergum is short, symmetrical and entire, 

 while in all the other genera it is more or less enlarged and 

 deeply divided into two asymmetrical parts (hemitergites), 

 which are sometimes completely separated. In the great 



