﻿I860.] • 127 



tion assume the pupal state at the end of the larval burrows, become 

 perfect and emerge during August ; but what becomes of these beetles 

 I do not know. I find no trace either of their ovipositing during the 

 autumn, or of their hyberuating ; for, though S. destructor begins its 

 burrows earlier than the other Scolyti, it is several weeks later than 

 the Hylesini and other bark beetles that pass the winter in the perfect 

 state. The greater number of the larvae when full fed burrow about 

 half-an-inch into the wood, where they form a little longitudinal 

 chamber, the entrance of which is tightly filled with frass, and in this 

 they pass the winter in the larval state, completing their transformations 

 in this cavity in the spring, and emerging abont the end of May. In 

 trees with tolerably thick bark, they sometimes form their hybernacula 

 in the latter. 



The object, though not the cause, of this difference in instinct 

 between the beetles emerging in autumn, and those remaining as larvae 

 until spring, is obvious. 



The bark, especially when riddled by Scolytus, soon becomes loose 

 from the action of the weather during the winter, and, when it falls 

 off, birds and numerous enemies quickly remove all exposed larvae ; but 

 those buried in the wood are quite safe, the little circles of frass mark- 

 ing their openings, when the wood has lost the slight staining it receives 

 from the decomposing bark, being hardly visible, though the little 

 patches of white wood frass in the removed bark, are very conspicuous. 



I do not remember having seen a felled elm trunk that $. destructor 

 had not attacked, frequently whilst still trying to throw out shoots ; 

 yet I have never seen a trace of it in healthy growing trees ; these are 

 supposed to resent and repel the attacks of the Hylesinidce by pouring 

 out sap into their burrows ; and, in the case of S. pruni, I have obser- 

 ved burrows less than an inch long, some of which, containing a few 

 eggs already laid, had been abandoned uncompleted by the beetles, 

 apparently on account of the presence of a fluid which must have been 

 sap, as no rain had fallen to account for it : these burrows had been 

 formed in bark that was still nearly healthy, though near some dying 

 bark which had doubtless attracted the beetles. 



3. Scolytus multisteiatus, Marsh. This also lives in elm, 

 being usually found in the same logs as S. destructor, though also 

 occurring in smaller ones down to four inches in diameter. It is much 

 more scarce than S. destructor, one of its burrows being found for fifty 

 of the latter insect. The burrows, similarly to those of S. destructor, 

 start from the bottom of a crevice in the bark ; they take a longer 



