188 PLUM. 



that a quantity of beetles which I secured in a tube buried 

 themselves so rapidly in the cork, that between the 10th of 

 September and the morning of the 12th they had already 

 bored five tunnels into it, and it contained at least seven 

 female beetles. 



A great peculiarity of this attack has been considered to be 

 the extreme rarity of males compared to the number of females, 

 and amongst from about fifty to sixty of these Shot-borers 

 which I took out of their borings in Plum stems in September, 

 I found only one male. Subsequent search, however, made 

 me think that in winter the difference in proportion of 

 numbers would be found to be not nearly so great, for amongst 

 some specimens I examined early in December I found a 

 larger proportion of males, and about a month later, amongst 

 specimens I took (on or about January 10th) from a piece of 

 Plum stem two inches and a quarter across, about seventeen 

 males to six females. 



The borings at this winter time of year only contained a 

 sprinkling of beetles, instead of, as in September, being so 

 crowded up that there was scarcely room to insert another 

 beetle into the row that filled each boring. 



The method of attack is stated, by the well-known German 

 observer Schmidberger, to be for the beetles to choose a spot, 

 usually on the main stem of the tree, making no distinction 

 as to the tree being sickly or healthy, young or old, so long as 

 it is thick enough for the purpose, — at least half an inch in 

 diameter. (The attacked stems sent me from Toddington were 

 from a little under to a little over three-quarters of an inch 

 across. — E. A.O.) The female then proceeds to bore passages, 

 and in a small chamber at the opening of each of these she is 

 stated to lay her snow-white, longish eggs. The first-hatched 

 larvae are recorded by Schmidberger as being noticeable about 

 the end of May, and these are considered by him to arrange 

 themselves (in the same manner as the beetles we noticed, as 

 above described), one after the other in the tunnels so as to 

 fill them, and to feed there on a whitish substance with which 

 the passage is incrusted, and there the maggots, according to 

 the observations quoted, turned to chrysalids and thence to 

 beetles.* 



The nature of this incrustation, now known to be fungoid, 

 is of great interest, and has been the subject of much dis- 

 cussion from the time of Canon Schmidberger, who described 

 this substance (of which the nature was not then known) 



* Bostrichus dlspar, Schmidberger (Apate dispar, Fab.) ; Xyloterus dispar, 

 Erichson. See ' Naturgeschichte der Schadlichen Insecten,' von Vincent 

 Kollar, pp. 261-273 ; and English translation, ' Kollar's Treatise on Insects,' 

 pp. 254-2(32. 



