SPRUCE BUD-WORMS. 847 



29. The black-headed spruce bud-worm.* 

 Teras variana Fernald. 



This caterpillar is so commonly met with on the spruce and fir that we 

 have given it the above English name, though there are other species 

 which have green bodies and black heads. We first met with it on the 

 terminal shoots of the black spruce on Peaks Island, in Portland Har- 

 bor, June 22, 1881, and also at Brunswick and Harpswell on the day 

 following, where it was associated with the caterpillars of the Sj)ruce 

 Bud-worm {Tortrixfumiferana). Unlike that species it does not, so far 

 as we have observed, cause any decided alteration in the appearance 

 of the shoots of the tree, not being social or abundant enough to strip 

 the leaves fron^ a single shoot, as in the case of the Spruce Bud-worm, 

 or the Eeddish-yellow Spruce Bud- worm {Steganoptycha ratzebitrgiana) 

 found on the white spruce last season. 



The egg-laying habits are not yet known, as none of the moths on 

 issuing from the chrysalis mated or proceeded to deposit eggs. 



The caterpillars usually live near the ends of the shoots, feeding on 

 the new leaves, which begin to grow out early in June ; cutting off the 

 tender leaves they make a passage way between them and the shoot, 

 which they line with white silk. When disturbed they rapidly crawl 

 out of their silken retreat and let themselves down to the ground by a 

 silken thread. They are very active in their habits and in confinement 

 in tin boxes will squeeze through the narrow space between the box and 

 the cover, so that only an unusually tightly closed box will confine 

 them. Sometimes, at least in two instances, the caterpillars constructed 

 a case of the leaves which they had cut off at the end of a fresh bud. 



The caterpillars were very abundant in 1881 in spruce and firs on 

 the shores and islands of Casco Bay, from June 10 until July 20. As 

 full-grown larvfB are abundant during the early part of June, it seems 

 that it hibernates among the shoots of the tree during the winter, and 

 that as in the case of the Spruce Bud- worm {Tortrix fumiferana) it 

 hatches in August, or at least late in the summer, and becomes nearly 

 fully grown before cold weather sets in. 



The caterpillar when fully grown is of.the usual shape of a leaf-roller, 

 deep green, with a dark reddish head and cervical shield ; before the 

 last molt the head and prothoracic or cervical shield are black. 



From the 14th to the 16th of June the caterpillars change to chrys- 

 alids within the slight white cocoon they spin among the bases of the 

 leaves next to the shoot. The moths begin to issue early in August, 

 and continue to appear until the middle of the month. In one case the 

 insect pupated from July 6th to the 10th, the moth issuing on the 19th ; 

 hence the pupal period lasts about two weeks. Others which x^upated 

 July 14 to 16 appeared three weeks later. None of the insects lingered 



* Extracted from U. S. Department of Agriculture, Division of Entomology, Bulle- 

 tin No. 12, p. 17. 



