IXTRODUCTIOX. 



in a group of Australian genera (Corynopliyllm, etc.), the females 

 of which are sluggish and rarely found, and the males have the 

 antennal club so greatly enlarged as to form their most conspicuous 

 feature. 



In the EUTBLIN.B some degree of elongation of the club is 

 almost general in the male, but the greatest development is found 

 in certain species of Anomala (A. macrophyUa, communis, and 

 allied forms). In these it is generally found that the female is 

 rare, or at least more rarely captured than the male, the reason 

 being, not necessarily that the actual numbers of the sexes are 

 very disproportionate, but more probably that the females are 

 sluggish in their habits and expose themselves less to the risk of 



a. b. 



Fig. 5. Adoretus versnfus : a, male ; b, female. 



capture than the males. The enlargement of the sensory surface 

 of the antennae of the latter probably implies a corresponding 

 delicacy of the sense of smell, and, like the enlargement of the 

 eyes, which often accompanies it, has become necessary in conse- 

 quence of the need for seeking out the females in their retreat. 

 The enlargement of the eyes is always accompanied by a reduction 

 in the size of the clypeus, and this form of sexual disparity 

 occurs in both Anomala and Adoretus, becoming most accentuated 

 in the Adoretus group. It seems to be peculiar to species of 

 nocturnal habits, and is found in some degree in nearly all the 

 A DOIIETINI, producing in many species, like the very common 

 Adoretus versutus (fig. 5), a marked dissimilarity between the two 

 sexes. Perhaps the extreme development is found in HeteropJi- 

 thalmus ocidaris, a rare insect occurring in Southern India. 



The second group of sexual characters is formed of those 

 directly concerned in the reproductive functions, most of them 

 consisting of modifications of the claws and feet of the males, 

 which apparently increase their grasping power. A feature 

 already mentioned, viz., an enlargement of the inner claw of the 

 front foot, often accompanied by more or less thickening of the 

 front tarsus and shorter and sharper teeth upon the front tibia, 

 is found in the great majority of the EUTELIN^E. In most of the 

 AXOMALINI the front inner claw is broadened into a flat plate, 

 often abruptly bent near its base, and capable of being folded 



c 



