NO. 2242. MORPHOLOGY OP THE STREPSIPTERA— PIERCE. 411 



Mesothorax. — The mesothorax throughout the order is small and 

 reduced, but not so much as the prothorax. Normally it is ring-like. 

 The mesonotum of Triozocera texana (Mengeidae) is transversely 

 faintly divided into two parts, the front probably best considered as 

 the scutum and the posterior part the scutellum. The elytra or bal- 

 ancers are club-shaped and attached near the front of the pleural 

 zone. They have a tiny hook at base, which probably assists in the 

 noise making produced when the elytra are in vibration. The pleural 

 zone immediately beneath the attachment of the elytra is broadly 

 lobately produced and has the anterior edges rough. This may serve 

 as a sort of drum. The lobe is the episternum-(-epimeron, and prob- 

 ably includes the trochantin in its posterior hook to which the coxa 

 is attached. The sternellum is quadrate and longitudinally divided ; 

 the eusternum is a transverse band laterally enlarged and partially 

 merging in the episternal lobe. It is depressed in the enlarged por- 

 tion and bears a long stigmatal opening (pi. 64, figs. 2, 5). 



There is a distinct anal lobe on the elytron of Xenos auriferi, 

 Stylops championi, and Neostylops Shannoni. It has not been noticed 

 on other species (pi. 70, fig. 6). 



Tetrozocera santchii (Mengenillidae) has a simple band-like me- 

 sonotum, but the mesosternum has three transverse areas, the pres- 

 ternum, eusternum, and sternellum. The latter is longitudinally di- 

 vided, each half being triangular with the coxae attached at the lat- 

 eral angles. The epimeron is only visible from the side (pi. 66, 

 fig. 2). 



In Muirixenos dicranotropidis (Halictophagidae) the mesonotum 

 consists of three transverse distinct areas — the praescutum, scutum 

 and scutellum, and postscutellum (pi. 76, fig. 1). These areas are 

 also distinct but diiferently formed in Pentozoe peradeniya., and 

 Dacyrtocara oncometopiae (pi. 74, fig. 1). 



In Delphacixenos onomalocerus only two transverse dorsai areas 

 are distinguishable, the front piece being praescutum. This condi- 

 tion is also found in Pyrilloxenos compactus. 



Dacyrtocara oncometopiae has the eusternum large, triangular, 

 extending between the hooks of the sternellum. The episternum is 

 large, lobed beneath the base of elytra, and posteriorly forms with 

 trochantin the hook to which the coxa is attached (pi. 74, fig. 2). 



Pyrilloxenos compactus has the most parts to its mesosternum 

 of any species examined. The eusternum is large, triangular, as in 

 the preceding, and separates the two hooks of sternellum. The 

 half ring, at the ends of which coxa is attached, consists of three 

 distinct parts, sternellum, precoxale, and trochantin. The pleural 

 suture separates episternum and epimeron to the tips of the hooks 

 formed with trochantin (pi. 77, fig. 3). 



The middle legs are like the anterior legs except that in the 

 Halictophagidae the first tarsal joint is usually mucronate. The 



