78 ENTOMOLOGICAL SOCIETY 



Hubbard, at Detroit, Mich., the only other injurious insect 

 associated with it being Agrilus torpidus. The present year 

 X. politus infests, in large numbers, large trees of Negundo 

 aceroides and Fraxinus sambucifolia growing along the Potomac 

 near Washington, and which had been partially decorticated 

 or dislocated by the great freshet of June 2, 1889. Many of 

 the trees show already unmistakable signs of decay. Last 

 August I found at Bladensburg; Md., a moderate-sized soft 

 maple tree which had been thrown down by the wind, and in 

 which the beetles were at work. I made a cross section 

 through one of the burrows, and it can be seen therefrom that 

 there is a slightly undulating main gallery leading horizontally 

 into the wood for a distance of about 70 mm. A longitudinal 

 section through this gallery shows that at about its middle, 

 and both above and below, it is intersected by a number (5 in 

 the specimen exhibited, but the number no doubt variable) of 

 rather closely placed perpendicular galleries (larval cradles), 

 averaging each about 15 mm. in length. They are of the 

 same width throughout as the main gallery, thus showing 

 that they have also been excavated by the parent beetle. The 

 whole work resembles that of Monarthrum mali, but in 

 Xyloterus the perpendicular galleries are a little longer. The 

 walls of all galleries are stained with black, and this serves to 

 distinguish the work of Xyloterus from that of a Ptinid beetle, 

 Ptilinus rujicornis, which was boring in the same maple tree, 

 and which excavates a simple gallery also leading deep into 

 the wood, but without any branches, and its walls never 

 stained black. 



XYLEBORUS FUSCATUS AND X. PUBESCENS. A very large 

 colony of these Scolytids was found by Mr. Ulke and myself 

 in the mountains at Pen-Mar, Pa., on August 2, infesting a 

 stump of a large butternut tree (Juglans dnerea) which had 

 been felled at least one year before.* Both species are true 

 wood-borers, and I am unable to distinguish their galleries, 

 which occurred promiscuously in the stump. Owing to the 

 want of proper instruments, and on account of the hardness of 

 the wood, only fragmentary portions of the galleries could be 

 secured. The work of the beetles consists of a long hori 

 zontal gallery leading straight, or slightly obliquely, or 

 slightly undulating, into the wood for a distance of at least 

 60 mm. Branching off at nearly right angles to the right or 

 left, and at intervals of about 1-5 mm., are several (two or 

 three, and perhaps more, on each side) lateral horizontal gal- 



* The stump was at first taken by me as that of a walnut, but I am in 

 formed by our best authority, Mr. B. E. Fernow, that it is a butternut. 



