354 Annals of the Carnegie Museum. 



to this species. Tliey come from Corumba and Para, Brazil (H. H. 

 Smith). A single small female (25 mm. in length) coming from 

 "Dutch Guiana" (O. G. Schultz) is also referred here. A still more 

 depauperate specimen (22 mm.) labeled "Santa Cruz de la Sierra, 

 Prov. del Sara, Bolivia, 1909, J. Steinbach" may also belong to this 

 species. 



In the writer's private collection are specimens of didactylus taken 

 in several of the West Indian Islands and various parts of South 

 America. 



8. Scapteriscus vicinus Scudder. 

 Scapterisciis vicinus Scudder, Mem. Peabody Acad. Sci., I (1869), p. 12, PI. i, 

 figs. 4, 23; KiRBY, Syn. Cat. Orth., II (1906), p. 2. 



Habitat. — Specimens classified as this species bear the following 

 labels: " Puerto Suarez, Bolivia, Nov., '08-Jan., '09 (J. Steinbach)," 

 five females; "Sta. Cruz de la Sierra, Prov. del Sara, Bolivia," one 

 female, also taken by J. Steinbach. The writer also possesses a 

 single female specimen, which he took at Las Pal mas, Chaco, Argentina, 

 in 1897. 



Synopsis of the South American Genera of Tridactylid/E. 

 A. Body smooth, punctate. Head directed anteriorly, narrowing towards the 

 front; ocelH arranged in a transverse line. Middle tibiae fusiform. In- 

 ferior anal appendages styliform. Wings nearly normal. 

 b. Size usually more than 5.5 mm. long. Pronotum furnished with a delicate 

 transverse, but well-defined sulcus near the middle of the anterior half. 

 Front tibiae of males sometimes deeply fissate; hind tibiae with three or 

 four pairs of long natatory lamellae, preceded by slight serrations, and 

 armed at the tip on either side with two very unequal calcaria, the longest 

 scarcely longer than the metatarsus, the only member of the tarsus present. 



Tridaclylus. 

 bb. Size usually less than 5.5 mm. in length. Pronotum without a well-defined 

 transverse sulcus. Front tibiae of male never fissate. Hind tibiae with 

 a single pair of natatory subapical lamellae or none; the margins of the 

 hind tibiae usually, but not always, smooth, armed at the tip on either side 

 with two very unequal calcaria, the longest about half as long as the tibiae, 



the tarsus wholly wanting, or at least practically invisible Ellipes. 



A A. Body velvety. Head vertical. Ocelli arranged in an arcuate line. Middle 

 tibiae slender. Infeiior anal appendages compressed. Wings with the 

 anterior field horny, smallest, the posterior field largest Rhipipteryx. 



Genus Tridactylus Olivier. 



Tridaclylus Olivier, Enc. Meth., Ins., IV (1789), p. 26; Latreille, Hist. Nat. 

 Crust., Ins., Ill (1802), p. 276; Saussure, Rev. Suisse Zool., IV (1897), pp. 

 407-419 and authors in general to date. 



