68 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I25 



Posterior sucker. — Disc-shaped structure at the posterior end of the larva, con- 

 taining numerous rows of hooks that are arranged radially as well as concentri- 

 cally along its periphery ; serves to fix the larva on the substratum. The number 

 of radial rows of hooks serves as a good diagnostic character. 



Pseudopod. — A single conical, truncate, soft, footlike appendage on the ventral 

 surface of the thorax which has on its apex numerous rows of hooks ; also called 

 the "thoracic prolog" or "anterior sucker." The pseudopod is used by the larva 

 for its peculiar type of motion. 



X-shaped sclerite. — Sclerotized area forming an X on dorsum of eighth ab- 

 dominal segment, the anterior arms of which extend toward either side of the 

 anus (or anal gills) and the posterior arms of which pass along all or part of the 

 margin of the posterior sucker. 



KEYS TO THE SIMULIIDAE OF GUATEMALAs 

 GENERA, BASED ON EXTERNAL CHARACTERS OF THE MALES 



1. Pedisulcus present on second segment of hind leg Simulium Latreille, 1802 



Pedisulcus absent 2 



2. Cu2 arcuate, discal cell present ; basitarsus of hind leg spindle-shaped, shorter 



than tibia; the calcipala present but rather short. . .Cnephia Enderlein, 1921 

 Cu2 straight, discal cell absent ; basitarsus of hind leg parallel-sided, approxi- 

 mately equal to length of tibia ; the calcipala very well developed, long, and 

 almost as broad as basitarsus itself Gigantodax Enderlein, 1925 



GENERA, BASED ON MALE GENITALIA (ALTERNATE KEY) 



1. Clasper cone-shaped, with more than one terminal spine 2 



Clasper cylindrical, quadrangular, or in other form ; if conical, then with only 



one terminal spine Simulium Latreille, 1802 



2. Clasper with two stout terminal spines both emerging approximately at apex ; 



body of adminiculum broader than long Cnephia Enderlein, 1921 



Clasper with two stout terminal spines, one emerging at apex, the other defi- 

 nitely subapical ; body of adminiculum longer than broad. 



Gigantodax Enderlein, 1925 



SPECIES OF THE GENUS CNEPHIA, BASED ON EXTERNAL 

 CHARACTERS OF THE MALES 



I. Mesonotum clothed with long, narrow, yellow, scalelike hairs as well as with 

 short bristlelike black hairs ; basal three-fourths to all of Sc pilose 2 



6 Subsequent to the preparation of this monograph, Vargas and Diaz (1953a) 

 placed the subgenus Dyarella Vargas, Martinez, and Diaz, 1946, as used through- 

 out the taxonomic section of this monograph, in synonymy with Hemicnetha 

 Enderlein, 1934, and the subgenus Lanca Vargas, Martinez, and Diaz, 1946, in 

 synonymy with Psilopelmia Enderlein, 1933. In the same paper they synony- 

 mized Simulium {Dyarella) mathcsoni Vargas, 1945, with Simulium {Hemic- 

 netha) paynei Vargas, 1942. Vargas and Diaz (1953b) also gave a new name, 

 Simulium {Notolcpria) gonsalezi, to what has here been called Simulium 

 {Notolepria) exiguum Roubaud, considering the material from Guatemala and 

 Mexico to be distinct from the type material of exiguum which came from 

 Venezuela. 



