LEPIDOPTERA OF NEW YORK AND NEIGHBORING STATES 



19 



Antenna shaft 



Pedicel Vertex 

 ' Scape 



STRUCTURE 

 Imago 



The head (fig. 3) bears a pair of antennae, normally long and con- 

 spicuous, a large, minutely facetted compound eye on each side, in 

 many cases with a minute simple eye, or ocellus, just above it ; and the 

 mouth parts, which include the labrum, a pair of mandibles, a pair of 

 maxillae, and the labium. 



The antenna is composed of a large number of segments, most often 

 from twenty to fifty. The 

 basal segment, the scape (fig. 

 3), is much larger than the 

 others; the second, or pedicel, 

 contains a peculiar sense or- 

 gan; and the remaining seg- \ X^BRRSHT^N ">oi P 

 ments comprise the flagellum. 

 Frequently the distal seg- 

 ments of the flagellum are 

 thicker and shorter, forming 

 a club (figs. 5 to 7). In this 

 case the slender part of the 

 antenna is the shaft. The 

 club is usually without scales 

 on the under side, even when 

 the shaft is fully scaled, and 

 varies in form and structure. 

 In the primitive forms the club is fusiform (fig. 4) gradually thickening 

 and as gradually tapering to a point. It may be bent in the middle, 

 or hooked, as in the skippers (fig. 5), and the hook may vary in stout- 

 ness and length, and in the number of segments involved. The higher 

 butterflies, which have no hook, often show, by the asymmetry of the 

 terminal segments, how the hook has become vestigial. In some forms 

 the club is not sharply set off from the shaft (as in Feniseca), and 

 in a few Satyrids its past existence is indicated only by an abrupt 

 change in the color of the flagellum. Antennae which are not clubbed 

 usually taper to a point; those which have lost a club usually end 

 bluntly. 



The normal antenna is partly clothed with scales, which typically 

 form two rings about each segment or two bands on the dorsal side 

 (fig. 8), but always leave more or less extensive sensory areas covered 

 with minute hairs, which by contrast appear naked. In many lower 

 forms these bare areas are inconspicuous, but as a rule the under half, 

 more or less, of each segment is naked. Lepidoptera with clubbed 



FlQ. 3. SIDE VIEW OF HEAD (THOLEBIA 

 REVERSAUB ) 



