560 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxxvi. 



It is interesting to observe that the tegiihi {T(/) is represented in 

 both the fore and hind wings of nearly all Orthoptera by a small 

 hairy pad on the axillary membrane between the base of the costa 

 and the attachment to the notum, 



V. PLECOPTEKA. 



Species studied. — Pteronarcys ((difovnica adult (72, 75, 78, 79, 

 wings 182, 183, 184), Tamioj>teryx fasciata adult, Perla sp. nymph 

 (73, 74, 76, 77). Aeroneuria sp. nymph (81), Isogenus sp. nymph 

 (80). 



Characteristics. — 1. Microthorax not well developed, consisting 

 generally of a chitinous band or plate on each side of neck. 



2. Trochantin {Tn) of prothorax in both nymphs (73) and adults 

 (72) inserts itself between coxa and true pleurum formed of epister- 

 num (i^/w) and epimerum {Epm). Upper part of trochantin {Tn) 

 then takes on both the function and appearance of the displaced 

 pleurum. It articulates with dorsal edge of coxa by a special con- 

 dyle {Tn CxP). presents externally a pseudopleural trochantinal 

 suture (72, Tn S) and internally a pseudopleural trochantinal ridge 

 (74, Tn R). Continuing above the latter on true pleurum is the real 

 pleural ridge {PP). 



3. Trochantin of both mesothorax and metathorax fused in adults 

 (78, 79, Tn) with episternum {Eps)., apparently not taking part in 

 coxal process {CxP). A nymph of Acroncnria (81) is similar but 

 one of Isogenus (80) presents a very typical trochantin {Tii) in the 

 mesothorax. 



4. Wing bases very simple, parts of typical arrangement (182, 183). 

 A triangular plate (6') of head of costa articulates with parapterum 

 (78, 79, P). Wing venation shown by figs. 183, 184. 



5. Meso- and nietanotum divided topographically into regions (75) 

 but not by lines or sutures. V-ridge absent. 



6. Plecoptera dift'er from Orthoptera in specialized condition of 

 prothoraeic pleurum and in development of pseudonotum in both 

 meso- and metatergum. 



VI. t'OKKODENTIA. 



species studied. — Cerasfospi/ni.s venosus (82). 



Characteristics. — 1. Microthorax presents elongate plate on each 

 side of neck, connecting with triangular lobe on posterior rim of 

 head, and with an arm on edge of prothoraeic episternum. 



2. Prothorax reduced, but all plates present except a preepis- 

 ternuni. Epimerum largest plate. Trochantin does not articulate 

 below with coxa. 



3. Dorsal plates of meso- and metathorax (mesonotum and pseu- 

 donotum and metanotum and pseudonotum) all fused so that meso- 

 and nietuteriia are solidly continuous. 



