48 INJURIOUS AND USEFUL INSECTS 



the galleries worked in the deep layers of the bark. The main 

 galleries are longitudinal, i.e. running upwards and downwards 

 in the erect tree ; they may be 8-10 centimetres long (3-4 in.), 

 but hardly ever reach 12 cm. (5 in.); sometimes they do 

 not exceed 2| cm. (i in.). From these main galleries pass 

 off radiating passages, which are narrow at the place of origin, 

 but widen gradually as they get further away from the main 

 gallery. They are often sinuous, and now and then join 

 other passages, either of the same or of another system. 

 These two kinds of galleries are the work of the beetle in 

 different stages of growth. The main galleries are wrought 

 by female beetles, and may be called " mother-galleries " ; the 

 radiating passages are mined by larvae, and may be called 

 " maggot-galleries." The history of their construction is as 

 follows : — The first beetles of the year emerge from their cells 

 in the wood of the elm towards the end of June. The females 

 soon set to work, and excavate a passage into the bark, 

 generally beginning in the bottom of a deep crack. The 

 males wander about the surface of the tree, and mate with 

 females, which are not yet completely buried in the bark. The 

 fertilised female continues her excavation along the trunk, and 

 from time to time makes a rude cell, which is merely a slight 

 enlargement of the gallery, now on this side and now on that. 

 In each cell she lays an egg, and a hundred or more have 

 been counted in one passage. The mother-gallery is finished 

 in about three weeks ; as soon as it is ready and stocked with 

 eggs, the female dies, and her dried-up body will be found in 

 some part of the mother-gallery. The larvae quickly hatch out, 

 and begin to mine. Each excavates its own maggot-gallery, 

 which though at first narrow, widens as the larva gets bigger 

 and stronger. In the widest and furthest recesses a few of 

 the full-fed larvae undergo their transformation, pupating 

 towards the end of July, and emerging as beetles during the 

 following month. The majority, however, prepare for winter- 

 ing in the tree. Each excavates a little chamber half-an-inch 

 or so deep in the wood, packs the entrance with wood-dust, 

 and there lies concealed and motionless till spring. Then 

 they pupate, and emerge as beetles in May. The advantage 

 of the deep excavation is not hard to perceive. Winter rains 

 and frosts are apt to loosen the bark of a dead or dying tree, 

 and so might expose larvae, resting in galleries excavated 



