16 EUTELIN^. 



another. But there are certain indications by vvliich the sex may 

 be accurately determined in abiiost every ease without difficulty. 

 Thus throughout the Adoebxini it will be found that the female 

 has the abdomen more or less convex beneath and the pygidium 

 very short and little exposed (fig. 4,d), while in the male the 

 abdomen is arched or hollowed a little from the base to the 

 extremity, and the pygidium is comparatively long, protuberant, 

 and exposed (fig. 4, c). 



In the Anomalini the shape of the last ventral segment pro- 

 vides a constant distinction. In the female it is triangular or 

 semicircular, that is, its widest part is in the middle (fig. 4, a). 

 In the male tliis is never the case, the segment being short, its 

 hinder edge more or less excised and the excision filled in with 

 a smooth shining membrane (fig. 4, b). The male may also be 

 recognised by the dilatation in some degree, sometimes very great, 

 of the inner claw of the front foot. 



In the PA.RASTASIIISI, although Sexual Dimorpliism is more pre- 

 valent than in any other group of Rutelin^e and assumes a greater 

 variety of forms, there is no single and invariable distinguishing 

 feature by which the sex of a specimen can be easily recognised, 

 •but a careful examination of the abdomen will reveal in the 

 majority of cases a certain characteristic difference of form. In 

 females the hinder part is more protuberant and pointed in shape, 

 while in the males it is more or less shortened, and the last dorsal 

 segment (pygidium) is more vertical in position. Another fre- 

 quently-found difference is in the shortening and thickening 

 of the front tarsi of the males, generally accompanied by a dilata- 

 tion of the inner claw, as in the Anomalini. 



In the General Introduction to the Lamellicornia of India, 1 

 have expressed my opinion tliat the most striking examples of 

 Sexual Dimorphism are to be regarded as due to a hypertrophy 

 of parts of the anatomy of the male which have ceased to have 

 any functional importance. Although a few remarkable examples 

 of this class are found in the Eutelin^, they are quite excep- 

 tional, but there are two other classes which appear here in 

 considerable variety, although not well represented in the groups 

 previously dealt with. 



The first of these classes concerns the sensory organs, which, 

 as in insects of most orders, are subject to specially high develop- 

 ment in the male. Particularly in cases where the female is 

 wingless or inactive, the antennse of the male may assume very 

 much enlarged or elaborated forms. Amongst the Pleurostict 

 Lamellicornia wingless females are practically confined to the 

 MelolonthiNjE, and it is in that subfamily alone that the club of 

 the antennae of the male is subject to any multiplication of the 

 number of joints composing it. In all othei's that number is 

 invariably three in both sexes, and any sexual modification is con- 

 fined to an increase in their size. Even this is almost unknown 

 in the CetoniiNjE, in which the two sexes appear to be equally 

 active. The same applies to the Dykastin^ as a whole, except 



