FAMILY SCOLYTIDAE 497 



the mature beetles were issuing from the tree, but there were no fresh egg- 

 galleries or eggs. On the other hand a large number of mature Phloeosinus 

 beetles had bored into the tree within the last week (between 14 and 20 June) 

 and laid their eggs in galleries grooved out in the bast. The insects were 

 also tunnelling into the green tree No. 4. 



This insect probably commences operations in the spring, laying 

 the first, batch of eggs of the year towards the beginning of May. In the 

 trees, however, I found only (i) mature beetles boring in in every instance 

 to lay the eggs of what I think was the second generation of the year, 

 (2) eggs laid by these latter, and in some cases (3) small larvae hatched 

 from these eggs which had already begun to bore away from the egg-tunnel. 

 As in the case of the Polygraphus, the male insect appears to be the first 

 to bore into the tree and commence hollowing out a chamber which grooves 

 the sapwood more or less deeply. He is soon followed by a female and 

 this latter by another till as many as four female beetles may have joined 

 the male, all five being found together, at this stage, in what is apparently 

 an enlarged pairing-chamber. From this the females, after pairing with the 

 male, eat out each a long clean irregularly curving egg-gallery, and lay large 

 eggs in depressions gnawed out at the sides, one in each. These depressions 

 are at fairly wide intervals apart, ten to twelve eggs being laid, about 

 half on each side of the gallery. These galleries are chiefly in the bast, 

 although they occasionally groove the sapwood. Fig. 22 shows a piece 

 of bark with the pairing-chamber, egg-galleries, and recess in which 

 the eggs are laid. From the eggs young larvae hatch out in a few 

 days, and then bore away from the egg-gallery more or less at right 

 angles to it. As I have taken only young larvae I do not know how 

 long these galleries are, nor where the larvae pupate, whether in the 

 bark or wood. The irregular winding galleries giving off all round form 

 a figure which is usually more or less circular in general shape, and is 

 easily distinguishable from the Polygraphus galleries, to which it has no 

 resemblance whatsoever. The egg-galleries are also much narrower and 

 smaller. The pairing-chamber averages an eighth of an inch across, whilst 

 the egg-galleries are from one and a quarter to one and a half inches in length 

 measured round the curves. The beetles mostly mature together, and issue 

 from the tree in a swarm. Such a swarm had evidently settled upon tree 

 No. 3, some from it having overflowed probably to tree No. 4. Although 

 there is not at present as much corroborative evidence available on the life 

 history of this insect as was obtained in the case of its more dangerous 

 confrere the Polygraphus, it is probable that the riilocoxiniis runs through an 

 identical number of generations; in fact, when a generation of mature beetles 

 of the former insect is found egg-laying in the trees, search will prob.ibK 

 show that there is a similar one of the latter at \\ork. The fact that they 

 prefer, however, drier bast, and the observations made in the forest, indicate 

 that the Poly^niphits is the first beetle to attack, its companion only coming 

 in when the vitality of the tree has been lowered. As a general rule, there- 



9003 i i 



