16 



found in the bark and wood, are followers, allies, dependents, or 

 natural enemies of one or more of the bark and wood miners. 



DESCRIPTION OF THE DESTROYER. 1 



This insect belongs to the order Coleoptera, the true beetles, which 

 are most distinguished in a general way by their hard wing covers. 

 It belongs to the family of beetles known as Seolytidre and to the genus 

 Dendroctonus. Up to the present time it has, together with several 

 other distinct but closely allied forms, been recognized by entomolo- 

 gists under the specific name rufipenntSj a name that was applied by 

 the English entomologist, William Kirby. to a species described by 

 him in 1835 from specimens collected on a journey from Xew York 

 State to the shores of Hudson Bay. It has been determined, however, 

 b} T comparison with the original specimens now in the British Museum 

 collections, 2 that the spruce-destroying beetle is quite distinct, and I 

 have applied to it the name Dendroctonus piceaperda, meaning spruce 

 destroyer. 



The adult (PI. II, figs. 1, 2) varies in length from three-sixteenths 

 to five-sixteenths inch (4.7 to 6 mm.), and in width from one-sixteenth 

 to nearly two-sixteenths inch (1.9 to 2.6 mm.). It also varies in color 

 from light yellowish in the } 7 ounger specimens to dark reddish-brown 

 and, in some mature individuals, nearly black. It will be more readily 

 recognized by the general observer from its common occurrence in the 

 bark of dying and recently dead spruce trees; also by the character 

 of its work, described and illustrated further on. 



The egg is a small pearly white object, scarcely to be distinguished, 

 if at all, from those of other bark beetles of the same size. 



The larva is, upon hatching from the egg, a minute, white, legless 

 grub (PI. II, fig. 1), which feeds on the inner bark and increases in 

 size until it has attained a diameter equal to that of the adult and a 

 length somewhat greater. It may be distinguished from any other 

 similar larva as yet found in the Eastern spruce by a dark yellowish- 

 brown space on the upper surface of each of the last two abdominal 

 segments (PI. II, fig. la). 



The pupa (PI. II, fig. 3) is nearly white, of the same size and some- 

 what the same form as the adult, but without free legs and wings, and 

 is found in oblong cavities in the bark of the trees where the broods 

 develop. 



1 Detailed technical descriptions will appear in a special paper to be published 

 later. 



- Specimens of the Dendroctonus collected from spruce in Maine, together with 

 specimens of another species from Hudson Bay and Lake Superior regions, were 

 sent to the British Museum and were compared, by Mr. Charles O. Waterhouse, 

 with Kirby "s types. He found that the one from Lake Superior agreed with the 

 labeled specimen, the one from Hudson Bay agreed with another, and the speci- 

 mens from Maine were different from any in the type series, 



