LEPIDOPTERA 



187 



bristles borne by the hind wing at the humeral angle (Fig. 329, /); this 

 is the frenulum. Its use is to insure the acting together of the two wings 

 of one side. As a rule the frenulum of the male consists of a single 

 strong spine and that of the female when present of two or more bristles. 



Jugum. — In one suborder, including only a few rare moths, there 

 exists, instead of a frenulum, a lobe borne near the base of the inner 

 margin of the fore wing (Fig. 333, p. 193) ; this is the jugum. See suborder 

 Jugatse. 



/?, *, 



/?, ^ 



Fig. 32g. — Wings of a moth: J h, frenulum-hook. 



Fig. 330. — Wings of Hemerocampa leucostigma. 



Discal cell. — Near the centre of the basal part of the fore wing there 

 is a large cell lying between veins R and Cu (Fig. 330); this is the 

 discal cell. In the more generalized Lepidoptera this cell is divided into 

 two parts by the base of vein M (Fig. 330, hind wing); in such cases the 

 cell lying immediately behind vein R is cell R, and that lying immedi- 

 ately behind vein M is cell M. 



Patagia. — At the base of each fore wing there is a scale-like ap- 

 pendage; these are the patagia or tegulae. 



In descriptions of Lepidoptera reference is often made to the palpi. 

 These form the double beak-like projection which extends forward from 

 the lower surface of the head. In most Lepidoptera only the labial 

 palpi are well developed; but in some of the more generalized forms the 

 maxillary palpi are also present. 



The presence or absence of ocelli is a character which is sometimes of 

 considerable importance. These organs are situated, one on each side, 

 above the compound eye and near its margin. But it requires some skill 

 to find them when they are present, on account of the long scales clothing 

 the head. 



The eye cap is also a character of some importance. The first seg- 

 ment of the antennas of some moths is much broadened and hollowed out 



