WORKINGS OF HVLESlNUS PRAXINI. 185 



in concert at the excavations, as the tunnel being always 

 free of incumbrance, and occupied by both Hi/lesini, the 

 rubbish could hardly otherwise have been passed from the 

 hole. At about half an inch at most from tiie entrance the 

 tunnel bifurcated (and pairing appeared to take place), the 

 two new tunnels being carried slowly on to right and left, 

 and almost at right angles with the first entrance passage, 

 till in about fire weeks they were at their full length, the 

 burrow having the appearance (as given in the figure) of a T, 



with truncate stem and elongated slightly arched arms of 

 various length, but not exceeding two inches. For the most 

 part, dining this time, one beetle was to be found in each of 

 the side galleries, but occasionally they were together, and 

 sometimes a third was present, the burrowings being entirely 

 inside the bark, so as to impinge chiefly on the bark itself, 

 but to leave a narrow white line along the floor, where the 

 removal of a narrow strip laid bare the white wood of the 

 tree. 



By the 4th of July most ot the Hylesini were dead in 

 their burrows, and a few of the channels of the larvae 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 j^laced side by side and at right 

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

 galleries pierced by the parent beetles. This arrangement 

 is a material check on the increase of the beetles, as the 

 larval galleries start so closely side by side under common 

 circumstances as only to leave space for the larvae in the 

 earliest stages of their existence ; with increase of growth 

 more room is needed. The strongest or swiftest get ahead 

 of their neighbours, and taking possession of the accom- 

 modation, leave the weaker grubs to perish ; and their tunnels 

 may be seen thinning into non-existence between the steadily 

 increasing size of tliose on either hand, so that of the larva: 

 that start evenly froui the egg frequently scarcely half the 



2c 



