114 



The arrangement of the branches of the burrow is somewhat irregular, 

 usually consisting of a few long straight galleries that are, roughly speaking, 

 parallel to each other. Sometimes a branch leaves another near its extremity 

 and returns nearly parallel to it, but they never anastomose. Sometimes they 

 consist of short curved portions continuously dividing dichotomously, making, 

 though not all in the same plane, a curiously regular pattern, something like 

 a branch of mistletoe. The much smaller burrows of Tomicus dryographus, 

 the only species we have in this country at all allied in habit to Platypus, divide 

 trichotomously with much more regularity than those of Platypus. 



The principal function of the parent beetle after ovipoSition appears 

 to be the ejecting of frass from the open mouth of the gallery, which they alone 

 appear to do. I have seen a small quantity brought every few minutes, at a 

 season when the larva? were busily feeding. It seems to be done by the male or 

 female beetle indifferently. 



I have strong reason to believe that either of these directs the move- 

 ments of the larvae in the burrows, not only from the burrows containing eggs 

 and young larvae being kept undisturbed, but also from larvae falling out of 

 burrows from which the parent beetle had been removed, a circumstance that 

 does not otherwise occur. 



The pupation cavities or burrows are excavated on either side, or I 

 should rather say on the floor and roof of a straight branch of the burrow, tole- 

 rably close together, so that the two sides of a burrow often contain several 

 dozen within a few inches. They are always at right angles to the gallery 

 from which they start, and also parallel to the fibres of the wood, of the same 

 width as the ordinary galleries, and just the length of one beetle. The larvae, 

 after excavating them, must come out and enter backwards, as the head of the 

 pupa is towards the burrow, and the larvae is unable to turn round in it. It is 

 shut off from the gallery by a slender partition of frass, which looks as if it had 

 got there by being pushed out of the way by passers by, and it is difficult to see 

 how it could be placed there in any other way, though as it in reality completes 

 the cocoon of the larva within it is hard to believe that its presence is thus as it 

 were accidental. 



I had usually found the pupation cavities placed vertically, i.e., one set 

 above the burrow, whose inhabitants must be head downwards, the other set 

 below the burrow, whose inhabitants must have the head upwards, it occurred 

 t ) me, in connection with certain theories as to the sexes of bees, to investigate 

 whether the different position had any influence on the sex of their inhabitants, 

 and I provided myself with a fine log occupied by Platypus for the purpose. I 

 found, somewhat to my disappointment, all the pupation cavities horizontal* 

 that being the direction of the fibres of the wood in the log. The beetles were, 

 I need hardly say, placed indifferently as regards the sexes. I tried to investi- 

 gate the matter in a suitable stump, but was not successful in finding many 

 beetles ready to emerge ; the few I found, however, did not favour any theory 



