ANTENNiE OF LEPIDOI'TERA. 5 



the scape, Fig. 26. Next it is the pedicel, which is smaller than the 

 scape, but larger than the segments immediately distad of it, except 

 among some of the Hesperiina and Papilionina. The scape and 

 pedicel together are often called the base, while all the remaining 

 segments make up the clavola. Among the moths the latter is often 

 pectinate, or feather-like, Fig. 8. There is much confusion in the 

 nomenclature of this form, ])ut in the following pages the general 

 form will be tei'med pectinate ; the })art made up of the bodies of 

 the segments, the shaft; and the projections, pectinations; Fig. 8, 

 sh. and pe. Among the skij)[)ers and l)utterflies the clavola is divided 

 into a proxinud, thread-like portion, the funicle, or stalk ; and a 

 distal, fusiform, or clavate part, the club. Figs. 4 and 5. 



The scape is inserted into a little cup-like depression of the head, 

 and is itself more or less rounded in at the i)roximal end. Very often 

 a constriction causes this end to take the shape of a spherical knob, 

 which, with the corresponding cavity in which it fits, makes a very 

 serviceable ball and socket joint. This permits great freedom of 

 motion in many planes, and to a considerable extent provides for a 

 rotary motion. The scape and pedicel also are joined in such a 

 manner as to allow considerable movement. The other joints, how- 

 ever, are comparatively stiff and afford little or no motion. 



HISTOLOGY. 



The scape is abundantly sup])lied with strong, striated muscles, 

 while in the other segments of all forms I have examined in sections, 

 I have been unable to demonstrate the presence of muscular tissue. 

 Fig. 20 represents a longisection of a segment with the two joints at 

 the ends and shows the shape of the contiguous parts. The chitinous 

 parts are held together by a tough, compact membrane, and it is due 

 to the elasticity of the latter that, when the clavola is flexed by ex- 

 ternal force, it is able of itself to resume its natural shape. A .sec- 

 tion of this membrane is well shown in fig. 18, me. Figs. 20 and 

 22 will make clear the internal anatomy of the clavola. Just entad 

 of the chitinous coat is a layer of varying thickness composed of 

 dermal and nerve-cells with numerous interlacing nerve-fibres. Along 

 the ventral part of the shaft runs ji large tracheal trunk supplying 

 the branches to the segments. Just dorsad of this trachea lie a pair 

 of large nerves wbieh come from the frontal ganglion and send out 

 branclies to the various organs of sen.se locateil in the antenna. The 



TKANS. AM. ENT. SOC. XXIII. JANUARY. 189(J 



