INTRODUCTION. XXVU 



visible oxtenially, but sometimes of very complex structure, cou- 

 •sliluliug the genital armature. 



The last dorsal segment is called the pygidium, and the penul- 

 timate the jyrojjygidium, when they are exposed beyond the elytra. 

 In the males of some genera, as in NitidulidsB, a small accessory 

 piece appears beyond the pygidium ; while in a large number of 

 Kliynch'ophora the pygidium is nearly equally divided in that 

 sex, so that the males have one more dorsal segment than the 

 females. 



The ventral segments may be either entirely free so that the 

 abdomen is flexible, or tliey may be more or less closely united, 

 so that the last alone is movable. The sutures separating them 

 are usually distinct when the segments are connate, sometimes, 

 however, visible only at the side; their line may be straight or 

 arcuate. 



The surface of the ventral segments presents no character of 

 systematic importance; often, however, sexual peculiarities are 

 observed, such as tufts of hair, spines, or tubercles, wliich may 

 be placed on any segment, but more commoidy on the terminal. 

 The latter is often emarginatc in the male, and in some Tele- 

 phorides assumes a degree of complication almost impossible to 

 describe. 



OTHER STRUCTURES. 



Besides the parts of the body above described, there are certain 

 structures occasionally seen, which, from being used for the dis- 

 crimination of genera, need our attention. 



Antennal Grooves. — These are grooves situated on the under 

 side of the head or prothorax.. When on the under side of the 

 head, they usually pass close to the eyes and converge on the 

 gula. "When on the under side of the prothorax they may be in 

 any ])osition from the line of the prosternal sutures to the thoracic 

 margin. Rarely the groove or fossa appears to divide the lateral 

 margin of the thorax in front as in some Dermestida?,, and in a 

 U\vf instances the opening of the fossa is visible from above as in 

 Murmidius, Bothriophorus, and Usechus. 



(irooves for the lodgment of the tarsi when retracted an; also 

 observed in some families (Eucneminse, Anobiinie); these may be 

 in tljc sternal i)ieces or on the ventral segments. 



