1900] COMMON ASH-BARK BEETLE. 11 



an inch in the ten days after first observation of the beetles. Opera- 

 tions were begun by a single beetle drilling a circular bore just large 

 enough to allow of its passage, where it was shortly joined by its com- 

 panion — the pair presumably working together at the excavations, as 

 the tunnel being always free of incumbrance, and occupied by both 

 Hylesmi, the rubbish could hardly otherwise have been passed from 

 the hole. 



At about half an inch at most from the outside entrance the tunnel 

 forked (and pairing appeared to take place), the two new tunnels being 

 carried on slowly to right and left, and almost at right angles with 

 the first entrance-passage, till in about five weeks they were at their 

 full length ; the bur rowings were inside the bark, so as to impinge 

 chiefly on the bark itself, but also to leave a narrow line beneath 

 the gallery on the outer white wood — this showing when a strip was 

 removed to gain a sight of the progress of working. From the 

 great amount of infestation, there was full opportunity of taking 

 observations. 



By July 4th most of the beetles were dead in their burrows, and a 

 few of the channels of the larvas begun, but not as yet in more than 

 one of each pair of galleries ; and about three weeks later these larval 

 tunnels might be found completed — usually placed side by side, and at 

 right angles, so far as circumstances allowed, of both of the side 

 galleries which had been pierced by the parent beetles. This very 

 regular position of the larval burrows (as figured at p. 9, magnified) is 

 characteristic, and is in itself to some degree a preventive measure to 

 excessive increase, for the larval galleries start so closely side by side 

 under common circumstances as only to leave space for the grubs in 

 the earliest stages of their existence, consequently, with increase of 

 growth more room is needed. The strongest grubs get ahead of their 

 neighbours, and, taking possession of the accommodatiou, leave the 

 weaker ones to perish, their tunnels thinning away into nothing 

 between the steadily increasing borings on either hand, as shown in 

 the figure (magnified) at p. 9. 



When the larvas of H. fraxini start side by side from the egg, I 

 found that thirteen might be counted to the half-inch ; whilst of those 

 which survived to the journey's end only seven found the requisite 

 space. Occasionally a whole line of eggs, or larvae, in their very first 

 stage failed to progress further in their development, the shiny specks 

 being noticeable, each in its own packing, along the side of the gallery ; 

 but without the external gummy skin which forms the usual protection 

 of the egg-chamber projecting slightly like minute studs along each 

 side of the tunnels formed by the parent beetles. The egg appeared 

 never to be deposited by the side of the short entrance passage, and 

 rarely just above the fork ; the space afibrded being usually occupied by 



