On Aquatic Carnivorous Coleoptera or DytiscidcB. 677 



I. 70.— Genus TIIERMONECTES. 



Coxal lines distinct in their hinder portion ; supra-articular border broad ; elytra 

 not punctate (except for a sexual sculpture in certain females). Middle femora 

 with elongate setpe. 



The species'^ may be arranged in three artificial groups : 



1. Elytra (at any rate on the basal portion) yellow with numerous black specks, 



after the manner of Rhantus. Nos. 1058 to 1064. 



2. Elytra black, with definite yellow markings forming conspicuous spots or 



fasciae, but no minute speckles. Nos. 1065 to 1070. 



3. Elytra black, with irregular marginal yellow marks which are of a longitudinal 



character and more or less divided by black lines and specks. No. 1071. 



Group 1. 



1058. Acilius nigrofasciatus, Aube, M.C. — Robustus, nitidus, lasvigatus, elytris 

 punctis seriatis sat conspicuis, subtus rufo-testaceus, supra testaceus, vertice 

 thoraceque transversim nigro-signatis, elytris nigro-irroratis, pone medium fascia 

 lata transversa, Integra, perconspicua nigra. Long. IH, lat. 7 m.m. 



Mas, lajvigatus, nitidus. 



Fem., elytris ad basin prothoraceque utrinque punctis elongatis, rudis impressis. 



In the male the three larger palettes on the underside of the front feet, are of 

 about one size. 



This species is extremely closely allied to the following, but is perhaps 

 really distinct, it is rather larger and comparatively broader in front, and has the 

 black fascia on the wing-cases excessively broad and conspicuous, and with no trace 

 of any interruption ; these are all the points I can find to distinguish the 

 male, but the female is very easily distinguished by its more conspicuous sexual 

 sculpture ; the elytra bear on their basal half coarse and deep short impressions or 

 elongate punctures, they extend all across the base of the wing-case from the 

 scutellum to the shoulder, and are also quite conspicuous on each side of the 

 thorax. 



I have seen but few specimens of this species ; the thoracic black marking is no 

 doubt variable, generally it consists of two transverse black lines, more or less 

 united at their outward termination, and separated from one another by about the 



* The descriptions mentioned in the following list also refer to this genus. Acilius cinctatus, Aube 

 (No. 1172 huj. op.), near No. 1070 ; Mexico.— Acilius laporti, Aube (No. 1174) near No. 1059 ; Brazil. 

 — Acilius laticinctus, Lee. (No. 117.5) near No. 1071 ; California. — AcUius maciilatus, Aube (No. 1176) 

 near No. 1059; Mexico. — Thei-monectes intermedius, Crotch. (No. 1508)? No. 1071 var. ; California. 



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