172 LETTERS TO MR. MARTIN [CHAP. XVH. 



a thread of silk, which are a good deal represented on the 

 inner surface of one of your pieces of bark. 



There are two or three grubs in fairly good condition 

 which I have gently inserted into a burrow in the little bit 

 of bark and have put carefully aside in the little box, and if 

 these develop, we shall then know what we have to deal 

 with. Perhaps you may be able to secure some beetles in 

 a month or two ; it would be of interest to make out the 

 attack with certainty. 



November 7, 1899. 



I have very carefully examined your beetle and find that 

 it is Hylesinus crenatus, sometimes known as the " Large 

 Ash-bark beetle " to distinguish it from Hylesinus fraxini, 



i, Beetle, with wings expanded, and one wing-case drawn only in 

 outline, to show lower part of wing ; 2, beetle as usually seen 

 magnified ; 3, smaller and paler variety ; also lines showing natural 

 length. 



FIG. 37. GREATER ASH-BARK BEETLE, HYLESINUS CRENATUS, FAB. 



the "Ash-bark" or the "Small Ash-bark beetle." The 

 life history of each kind is stated to be the same, and I 

 think, if I remember rightly, that some time ago, perhaps 

 a year or so, in the course of our occasional correspondence, 

 we have gone into the history of the fraxini, but if not I 

 should have pleasure in either looking up the account in 

 my Manual and sending the pages to you or condensing the 

 points. 



There appears to me to be this difference in method of 

 larval proceedings : that whereas in the case of fraxini the 

 parent galleries are formed somewhat in the shape of a T, 



