'J'lIE CATKllPlLLArv: STRUCTURE OF THE HEAD. 9 



upon the mandibles, tlic u]>[)vv l)asc of wliidi it serves to protect. The 

 inimdihles, one on either side, arc composed each of a short, very stout, 

 tumid, horny phite, broadening- from the l)asc apically, its apical edge more 

 dense, and either straight and chisel-like or somewhat serrated, the teeth 

 usually triangular (86:32). liehind the mandibles lies the basal portion 

 ..rtlu'Hiaxillae,— a fleshy mass bearing a large but short and somewhat 

 uKunmiform joint ; this in its turn bears an inner and an outer palpus ; 

 the inner is (mlinarily nuich the less conspicuous, and consists of only one 

 or two joints, which generally resemble, but are smaller than, the penulti- 

 mate or the apical two joints of the outer palpus ; the latter usually consists 

 of three joints, the apical two at least being of a partially horny consistency, 

 each of them cylindrical, equal, and usually much smaller than the pre- 

 ceding, the last being always minute and frequently almost imperceptible. 

 These two palpi are crowded together just at the base of the mandibles. 

 Occupying nearly the whole of the remaining portion of the under surface 

 of the head between the basal portions of the opposing maxillae, is the 

 lal)ium ; its basal portion resembles that of the maxillae ; it bears apically 

 on either side, just Avithin the inner base of the maxillary palpi, a pair of 

 minute, slender, two jointed labial palpi, the basal joint of which is com- 

 ])aratively long, the apical very minute ; between these two the apex of the 

 labium is peculiarly developed, being tumid and bearing on a swollen base 

 a small, conical, Jlender, depending, horny tube, forming the spinneret, 

 through an orifice in which the fluids pass when the insect spins silk. The 

 antennae, lying just outside the base of the mandiljles, are composed of 

 four joints ; the basal joint large, fleshy, mammiform, pressed upon by the 

 base of the widely expanded jaws ; the second much smaller, usually half 

 as long as broad, and having a somewhat horny consistency ; the thnxl 

 slenderer than the second, nuich, sometimes thrice, longer than broad, cy- 

 lindrical, nearly equal, abruptly truncate and bearing at its tip a very long 

 tapering bristle, usually much longer than the rest of the antenna ; beside 

 this bristle, but not in the middle, is situated an exceedingly minute fourth 

 joint, sometimes difficult to distinguish. The ocelli (86:24,25) are situ- 

 ated just behind and a little above the base of the antennae. They gener- 

 ally iiave the appearance of smooth hemispherical warts, some larger than 

 others and occasionally somewhat protuberant, sLx in number in most ma- 

 ture cateri)illars, of which five are generally arranged in a more or less open 

 and regular curve, whose convexity is forward and whose anterior limit is 

 frequently marked by a slightly impressed line ; the sixth lies behind the 

 others though at no great distance ; the genera differ somewhat in the varied 

 relations and exact position and size of the ocelli. 



The head varies greatly in general contour, especially about the summit, 

 which is occasionally produced into long, pointed horns, or bears elongated 

 thorny tubercles or "stout prickly spines. It is also generally covered to a 



