FAMILY SCOLYTIDAi: ' 553 



The first beetles of the year are found towards the end of April boring 

 nito the trunks of blue pine {Finns excclsa) or spruce 

 Life History. {Picca movinda) of all ages, from the pole stage upwards. 



When it has reached the bast the insect gnaws out an 

 irregular-shaped pairing-chamber, often as much as h in. by J- in. in size 

 (see pi. liii; pi. liv, p.^ When this is ready coupling takes place, 

 several female beetles entering by the same .tunnel and being fertilized 

 by the male. b>om two to four egg-galleries (the number is usually 

 three) are excavated, grooving both bark and sapwood, radiating from 

 the pamng-chamber (pi. liii ; pi. Hv, e), and more or less in the long 

 axis of the tree. These galleries, which contain generally only one air- 

 hole (pi. liv, ^0, i.e. a hole bored horizontally through the bark to the 

 outside to admit air into the egg-gallery, are from two and a half to three 

 inches m length, and are bored by the female beetles. On the right 

 and left, but apparently chiefly on the right, she eats out little recesses, 

 laying in each an egg, from twenty to thirtv being generally deposited 

 in each gallery. The galleries are blocked up with wood-dust. As only 

 one egg-gallery is bored by each female, it would appear that the beetle 

 pairs with two to four females. 



The first larvae make their appearance before the egg-laying is over, 

 and at once commence to eat out winding galleries in the bast,"^ which have 

 a general direction at right angles to the direction of the mother-gallery. 

 The greater number of the larvae appear to develop from the eggs laid on 

 the right hand of the gallery (see pi. liii ; pi. liv, /), as the mother bores 

 away from the pairing-chamber, so that the larval tunnels shall keep 

 clear of the neighbouring egg-gallery. As the larvae increase in size so does 

 the diameter of the tunnels they are boring; they go deeper into the bark, 

 and the whole plan of the mother and larval galleries remains indelibly 

 impressed on the bark long after the beetles have matured and left the 

 tree. The larval borings only slightly groove the sapwood, consequently this 

 latter only bears the impression of the p^airing-chamber and the egg-galleries 

 with the notches cut by the beetles for the reception of their eggs (see pi. xl). 

 In the case of an old attack, therefore, if one wishes to find out whether the 

 eggs hatched out and the larvae became full-grown, it is necessary to inspect 

 the bark on the inside in addition to the sapwood. 



The mother galleries are often as much as three inches in length, and 

 those of the larvae, which are usually very winding, one and a half to two 

 and a half inches. The larvae pupate at the end oftheir galleries in the bast 

 during the first days in June. Towards the middle of the month the new 

 beetles, now mature, leave the tree through round holes bored horizontally 

 through the bark from the pupating-chamber, and immediatelv attack fresh 

 trees and lay their eggs in them. The larvae from these eggs soon make 

 their appearance, and the resulting beetles issue about the beginning of 

 August. A third generation of beetles appears in the first half of October, 

 and from eggs laid by these the larvae of a fourth during October- 



