FIELD BOOK OF INSECTS. 



who mistake the long palpi for antennas. One of the 

 main groups in the family, the Helophorini (Helopliorus 

 and Ilydroclms are the principal genera), is made up of 

 small species which usually have the pronotum narrowed 

 behind, so that it is not as wide as the two elytra. The 

 others have it narrowed in front, the base being as wide 

 as the elytral base. Of these, the Hydrophilini and 

 Hydrobiini have the tarsal joints short. The metasternum 

 of an insect may be described as its breast-bone; it 

 is just in front of the bases of the hind legs. The meta- 

 sternum of the Hydrophilini is prolonged into a distinct 

 spine and that of the Hydrobiini is not. Finally, the 

 Sphaeridiini (late authors make them a separate family) 

 have the first joint of each middle and hind tarsus elon- 

 gated. Some Sphaeridiini, living in manure, decaying 

 sea- weed, and the like, have a wide distribution. 



As might be guessed from its generic 



Sphajridium name this insect belongs to the Sphasridiini; 

 scarabsoides , 



the specific name was suggested by the 



fact that it resembles the Scarabaeidss in looks and habits. 

 It is a European insect which was introduced in the latter 

 part of the last century ~and is rapidly extending its range. 

 It lives in dung. The adult is about a .25 in. long; has a 

 very convex back; shining black above except that the 

 elytra have a reddish spot near the base and the apical 

 fourth is yellowish. 



This genus (Plate LXXIV) contains the 

 Hydrophilus . 



two largest species (as well as some smaller 



ones) of the family. They are both shiny black. H. 

 ovatus is about 1.25 in. long; the abdomen, which is 

 unmarked, is pubescent except for a narrow, smooth 

 streak down the middle of the last three segments. H. 

 triangularis is larger, even reaching 1.5 in.; the under side 

 of the abdomen is pubescent except for a broad, smooth 

 streak down the middle of all but the first segment; the 

 abdominal segments have more or less distinct, triangular, 

 yellow spots at the sides. They are at times common 

 under electric lights. 



Hydrocharis is a related genus; obtusatus is quite convex 



294 



