460 FAMILY SCOLYTIDAE 



with a small, usually yellow head, and black or brown strong mandibles. 

 The larva is easily distinguished from the bostrychid larva owing to its 

 being legless. 



The pupa is white or yellowish-white in colour, soft, blunt elliptical, 



circular, or elongate in the wood-boring forms. The head 



Pupa. is hidden beneath the projecting prothorax, and the legs 



and wing-cases pressed close to the chest. When the 



pupa has gradually assumed the form of the future beetle, the latter re- 

 mains for a varying period in the pupal chamber in a resting stage. At this 

 period the insect will be usually light yellow or brown in colour, and is still 

 immature for identification purposes. On various occasions Scolytidae sent 

 from different parts of the world have been taken from the pupal chamber in 

 this resting stage, with the result that their determination has been im- 

 possible. The colour gradually changes from the light tints to darker browns 

 or blacks, whilst at the same time the outer parts solidify, and the insect is 

 then read)' to leave the pupal chamber. In many cases it quits the tree 

 by tunnelling straight through the layers of wood and bark between the 

 pupal chamber and the outer air. 



This family is peculiarly a forest-living one, the greater bulk of the 

 species probably ovipositing in forest trees or woody 

 plants, either in the bark or bast, or in the sapwood or 

 heart-wood. The mature beetles appear on the wing 



for short periods only, the greater bulk of a generation issuing from the 

 trees at the same time, and very often at night. This is one reason why 

 these insects are so rarely met with in the forest in the daytime, and 

 consequently why they have been so sparingly caught by collectors, and have 

 not found their way into collections. And yet, as will be shown, if a forest 

 officer or collector knows where to look for the insects, he will find them in 

 numbers should the search be instituted at one of the periods during the 

 year at which the insects appear on the wing. It is a common rule for 

 these insects to pass through more than one generation or life cycle in the 

 year, even in temperate climates. In India most of the species known pass 

 through at least two generations in the year, and the number may be four, 

 or even five in favourable seasons. Now, although the bulk of the individuals 

 o( any one generation issue at the same time, there are always some back- 

 ward members of any one brood. These may have been kept back by a cold 

 snap in a depression in which a few trees may be situated, or something may 

 have caused an interruption during the egg-laying by the parent beetle. 

 Oviposition in most cases would seem to be finished in a period of a week, 

 and consequently, under ordinary circumstances, the last-laid eggs appear to 

 mature into beetles almost as soon as those first laid, the difference being 

 probably not more than forty-eight hours. Should, however, anything 

 have occurred to interrupt the beetles whilst ovipositing, such as an outflow 

 of resin by the tree, the last-laid eggs will mature at a considerablv later 



