4 BULLETIN 598, U. S. DEPARTMENT OF AGRICULTURE. 



larva is at rest covers the head. The spreading side tufts give the larva a 

 depressed appearance. 



First instar (PI. II, fig. 1). — Width of head, 0.46 to 0.50 mm; total length, 

 1.5 mm. ; when full fed, 3 mm. The head is shining black and is much wider 

 than the thorax of a newly hatched larva. The body is cylindrical, pale green- 

 ish white, and marked with black setiferous tubercles. Dorsally the tubercles 

 appear as follows : On the first thoracic segment, a large dorsal plate and two 

 very small tubercles on either side; second thoracic segment, one large com- 

 pound tubercle on either side near the cephalic margin and a very small me- 

 dian tubercle near the caudal margin; third thoracic segment, 2 conspicuous 

 tubercles on either side; first to eighth abdominal segments, 3 conspicuous 

 tubercles on either side arranged In a triangle, two of them being near the 

 cephalic and one near the caudal margin ; ninth abdominal segment. 1 large 

 compound tubercle on each side ; tenth abdominal segment. 1 large plate cover- 

 ing most of the dorsal aspect of the segment. On all the thoracic segments and 

 on third to ninth abdominal segments there are 3 small tubercles on each 

 side; on abdominal segments 1 and 2 there are 4 on each side; and on ab- 

 dominal segment 10 there is 1 one each side. All the lateral tubercles and 

 lateral-dorsal tubercles bear 1 white seta. Black setse are all dorsal, 4 arising 

 from each thoracic segment, 1 from each of the 4 median abdominal tubercles, 

 and 6 from the anal plate. 



Second instar. — Width of head, 0.65 mm.; total length, 5 to 6 mm. when full 

 fed. This instar differs chiefly from the preceding in the abundance of long 

 whitish hairs which arise in considerable numbers from all the tubercles. The 

 tubercles are larger and contrast strikingly with the color of the body. 



Third instar. — Width of head from 1.12 to 1.16 mm. ; total length, 10 'mm. 

 when full fed. More hairy than the preceding instar. 



Fourth instar (PI. II, fig. 2).— Width of head, 1.7 mm.; total length, 13 to 

 14 mm. The dorsal tubercles are nearly obscured by the hair arising from 

 them. 



Fifth in s tar.— Width of head, from l.SS to 2.19 mm., average 2.1 mm.; total 

 length. IS to 19 mm. Tufts at sides of each body segment becoming conspicu- 

 ous, and the black pencils may appear in this instar. 



Sixth instar.— Width of head, from 2.91 to 3.09 mm., average 3.0 mm. ; 

 total length when full fed. 22 to 25 mm. The side tufts have become so con- 

 spicuous that they give the larva an almost flattened appearance. The black 

 dorsal tufts are not yet touching and do not yet form a conspicuous crest. 



Seventh instar (PI. II. fig. 3). — Width of head, from 3.43 to 3.52 mm., average 

 3.46 mm. ; total length. 27 to 32 mm. Practically the same as the preceding. 



Eighth instar.— Width of head, from 4.10 to 4.30 mm., average 4.2 mm.; 

 total length, 32 to 40 mm. This larva is very much like the preceding if it 

 has yet to pass through another instar, or if this instar is the last it is like 

 the mature larva previously described. 



Ninth instar (PI. I).— Width of head, from 4.7 to 4.9 mm., average 4.S mm.; 

 total length, 35 to 42 mm. This instar differs conspicuously from the imma- 

 ture forms because of the striking black crest. 



COCOON. 



(PL III, fig. 3.) 



The cocoon is usually ellipsoidal, sometimes slightly flattened on one side, 

 -.depending on the material which surrounds it. In length it averages 23 mm. 

 -and in width 15 mm. The larva mixes most of its gray hairs into the silk, 

 making the cocoon very hairy. In color it is dirty gray. 



