RHTN'CHOPHORA. 



285 



truncate or emarginnte at apex, but not (or very rarely, ami then not 

 strongly) bilobed ; the lobes at the sides of the thorax are distinct and 

 often partially cover the eyes, which are round ; the posterior coxae are 

 very broadly distant ; the scutellum is small ; the elytra have the 

 shoulders, well marked and are usually bluntly produced at apex; the 

 femora are simple ; the prosternum is broad before the anterior coxae 

 and is emarginate at apex ; the surface of the body is usually furnished 

 with a hydrofuge tegument, or in simpler language a covering which 

 repels water ; three genera have been regarded as British Hydronomus, 

 Ba<ions and Lyprus ; the latter of these has for some time been united 

 with Bagous, and Bedel appears to be right in also regarding Hydro- 

 nomus as a portion of Bayous, as the differences scarcely appear to be 

 generic. 



BAG-OUS, Schonherr (Hydronomus, Schouherr). 



About fifty species have been described as belonging to this genu*, 

 but as no less than' thirty-two have been found in Europe, and it is 

 known that representatives occur throughout Northern Asia and North 

 America, it is probable that the number will be very largely increased ; 

 species have also been described from Algeria, South Africa, Cuba, <fec.; 

 they are so extremely sluggish and retiring in their habits, which are 

 altogether subaquatic, that they are very seldom met with, so that 

 although no less than fourteen or fifteen species have been recorded as 

 British, they are, with few exceptions, scarcely represented in any 

 collections, and in list after list of localities the genus is returned as 

 almost entirely blank ; they are, however, gregarious, and in the 

 localities in which they occur, several of the species have been taken 

 by collectors who have found out their habits, in large numbers ; the 

 chief characters of the genus have been mentioned above ; in form and 

 general appearance the species greatly resemble one another, and they 

 ure in many cases difficult to determine except by comparison with 

 authentic specimens. 



The larva of B. (Hudrnnomus) alismatis has been observed by Kaltenbach ; it is 

 found feeding on the leaves of Alisma plantago and undergoes its transformations in 

 the part of the plant where the base of the leaf like a sheath enfolds the stem of the 

 plant ; the perfect insect appears at the beginning of the summer. 



The British species may be roughly distinguished as follows, but the 

 characters, in several cases, are not very satisfactory. 



I. Prosternum flat before the anterior coxae; antennae 

 with the first joint of the funiculns longer than 

 the second (Hydronomus, Schonh.) 



II. Prosternum with an excavation before the an- 

 terior coxae, which is margined on each side ; 

 antenna? with the first joint of the fnniculus about 



equal to the second (Ragous, i. sp.). 

 i. Club of antennas with the first joint glabrous 

 and as long as all the following joints united; 



B. ALISMATIS, Marsh. 



