On Aquatic Cat'nivorous Cuhoptera or Dytiscidce. 



705 



The species* are all South American and may be arranged in six groups as 

 follows. 



Size moderate, about 30 m.m. long ; a vague yellow 



lateral band on wing-cases; termination of meta- V- Group 1. (Nos. 1103 and 1104). 

 sternal wing far from epipleura. ) 



:l, 



Size small (about 22 m.m.); no yellow lateral band;) 

 apex of metasternal wing near to epipleura ; $ inner > 

 claw shorter and finer than outer one. ) 



Group 2. (No. 1105.) 



O 



Size small (about 23 m.m.); inner claw on hind foot of 

 males as large as the other ; apex of metasternal wing 

 near to epipleura ; with or without lateral yellow 

 band on elytra ; females with a beautiful sexual 

 sculpture. 



Group 3. (Nos. 1106 to 1109). 



Size moderate (29 m.m.) ; elytra with yellow stripe; apex ] 

 of metasternal wing near to epipleura; female V 

 without sexual sculpture. j 



Group 4. (No. 1110). 



Each sex with two claws of nearly equal length on hind foot; the 1 



smaller spur of hind tibia minutely tridentate or trituber- > Group 5. (Nos. 1111 to 1116.) 

 culate at the apex. j 



Two claws of about equal length on hind tarsus in each sex ; smaller )« e /-kt iii»7 jiiio\ 



f.,. , ,.,? 1 i" i-f i . i -i > Group 6. (Nos. 1117 and 1118). 



spur of hmd tibia largely biturcate at extremity. J 



Group 1. 



1103. Megadytes expositus, n. sp. — Ovalis, elongatus, sat convexus, nitidus, supra 

 olivaceus, vage testaceo-cinctus, subtus piceus, pectore prosternoque in mediis 

 olivaceo-metallescentibus ; pedibus quatuor anterioribus rufis, posterioribus piceis 

 trochanteribus dilutioribus ; pectore longitudinal] ter arcuate ; femoribus posteriori- 

 bus angulo externo spinoso-acuto. Long. 32, lat. I62 m.m. 



The male has the front tarsi small attaining only 2 to 2J m.m. in the transverse 

 direction ; the intermediate tarsi have long sexual hairs on the two basal joints, and 

 a slight tendency to a similar development on the third joint. The females have 

 a very fine and obsolete sexual sculpture on the wing cases, consisting of very fine 

 punctuation and some very short indistinct scratches along the middle towards the 

 base. 



•Reference should also be made to Cybister seneus, Orm. (No. 1274 luij. op.)! No. 1104 var. ; South 

 America. 



