6 INTRODUCTION. 



Zygaenids, &c. Thus the neuration of the extinct ancestor of the 

 Lepidoptera consisted of at least fifteen simple longitudinal veins to 

 each wing, and probably more, as in many groups vein 1 b of the 

 hind wing is forked at the base. 



The fore and hind wings of the majority of families of moths 

 are united by a " frenulum " arising from the base of the costa of 

 the hind wing and fitting into a " retinaculum " on the fore wing, 



Fig 6. 



1- d ; 2. $. A. Fore wing; B. Hind wing. 

 /. Frenulum. s.n. Subcostal nervure. 



r. Retinaculum. m.n. Median nervure. 



c.n. Costal nervure. i.n. Internal nervure. 



which consists of a fold from the underside of the costa, a hook 

 or tuft of hair arising from the lower side of the costal nervure, or 

 a tuft of hair arising from the upper side of the median nervmv 

 or rarely from the wing-membrane below it. The form of tin' 

 freuulum is of great use in determining sex, as in the males of all 

 the forms that possess it it consists of hairs firmly .soldered 

 together so as to form a single bristle, whilst in nearly all females 

 it consists of three or more bristles which are shorter than that of 

 the male ; in one female Cossid 1 have found as many as nine. Also 

 in the large majority of moths the retinaculum descends from the 

 costal nervure in the male, whilst in the female it ascends from the 

 median nervure. 



The abdomen consists of eight or nine segments, the number 

 varying in closely allied genera, so that the genital and anal open- 

 ings lie usually behind the eighth but somel lines behind the ninth 

 segment. The genital armour in the female is very simple, con- 

 sisting of two valve-like pieces, whilst in the male it is much more 

 complicated, forming long curved hooks for clasping the abdomen 

 of the female ; these are said to be of great use for specific and 

 but little for generic distinction, but the day is far distant when 

 they will have been sufficiently studied to be made use of. 



The tendency in Lepidoptera, as in other groups, is for forms 

 from the N.W. Himalayas to be large and pale, from the E. Hima- 

 layas and Burma to be large and dark, from the arid parts of 

 Continental India to be small and pale, from the moist forests of 

 S. India and Ceylon small and dark. Such geographical forms 



