INTRODUCTION. 61 



The stemmatic, or simple eyes, in the form of pel- 

 lucid spots, are usually two in number, and placed 

 on the crown of the head. They are probably of- 

 ten awanting, and, when present, are so indistinct, 

 from being covered by the hairs and scales that clothe 

 the surface, that their existence in any case among 

 the diurnal Lepidoptera has been sometimes denied. 



The antennae are of moderate length, and consist 

 of a great number of joints, which usually increase in 

 thickness towards the extremity, where they form a 

 club or knob: (PI. I. fig. 12, b). They are greatly 

 more uniform in appearance and structure than in the 

 coleopterous or most other tribes, or in the nocturnal 

 species of the same order, which often have them beau- 

 tifully branched, and plumose. The shape of the ter- 

 minal knob, however, varies considerably, and as its 

 different forms afford useful characters for distin- 

 guishing genera, they will be afterwards particularly 

 indicated. 



The thorax that portion of the body interme- 

 diate between the head and abdomen is composed 

 of three segments, so closely united as apparently to 

 form a single piece. Its most ordinary form ap- 

 proaches to cubical, any apparent deviation from that 

 shape being chiefly caused by the greater length and 

 density of the hairs and scales with which it is co- 

 vered. Before the insertion of the upper wings, 

 two corneous scales may be observed, covered with 

 tufts of hairs, so as to make them resemble an epau- 

 let : these have received the name of patagia, or 



