FAMILY SCOLYTIDAE 547 



commence to hatch out. The larva eats out a narrow tunnel in a 

 direction at right angles from the egg-gallery, and this larval gallery 

 appears to be invariably straight. This may be due to the hard straight 

 fibres of the oak wood ; but, whatever the cause, this habit of the grub 

 distinguishes it at once from other known Indian scolytid bark-boring 

 grubs, whose tunnels invariably serpentine ; also, owing to the fact that the 

 egg-galleries are at right angles to the long axis of the tree, i.e. go round the 

 tree, the larval galleries go straight up and down the tree. The plan thus 

 made is so different from any of the at present known Indian Scolytidae 

 as to render the presence of this insect in the trees easily recognizable. 



The larval galleries increase in diameter with the growth of the grub, 

 but do not groove the sapwood as deeply as the egg-galleries. 



The larva when full-grown eats out a depression in the sapwood at the 

 end of its gallery and pupates. On maturing from the pupal stage the 

 beetle eats its way through the bark which covers it, making a small 

 circular exit-tunnel in it, and escapes to seek out a good tree in which to 

 oviposit and carry on the attack. The presence of these numerous exit- 

 holes on the outside of the bark serves as an indication that the beetles bred 

 in it have left the tree. 



The pupating-chamber is one-fifth by one-seventh of an inch in si^e ; 

 the egg-gallery from one and a half to two inches in length, and the larval 

 galleries from one and a quarter to two and a quarter inches ; the number of 

 eggs laid is usually about twenty. 



This insect is a polygamous one, and the male pairs with three or four 

 females. In the case of the latter typically the egg-galleries of two of 

 the females are taken in one direction and those of the other two in an 

 opposite one, alternate beetles boring in opposite directions after pairing. 

 A plan similar to that shown in pi. lii is thus obtained. Practically, 

 however, it will be found that the direction of these egg-galleries varies, 

 and they may curve considerably; at times even it will be found that 

 three take off on one side and one only on the other; or again one or 

 two may be extremely long and a third very short, the fourth being absent. 

 These variations are doubtless due to differences in the physical capa- 

 bilities of the beetles themselves and to variableness in the hardness of 

 the wood, such as knots, etc. After pairing with the females the male dies 

 in the pairing-chamber. 



This beetle is an active little insect, leaving the trees in daylight, which is 

 unusual with Scolytidae, and walking and flying actively about in the sunlight. 



From observations made towards the end of May it is evident that 

 a generation of the beetle was then just maturing and issuing from the trees. 

 This generation of the beetles is probably the first generation of the 

 year, and it is certainly followed by a second, since larvae from eggs laid 

 by it were taken from the trees in June. It is probable that there is 

 at least a third generation of beetles during the year, from eggs laid by 

 the second generation, which probably issues in August. This point, how- 



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