194 THE CANADIAN ENTOMOLOGIST. 



When egg-laying is completed the adults usually die, and their 

 remains may frequently be found long after in the tunnel. Some species, 

 however, cut a new tunnel and rear a second brood. With certain species, 

 e. g., Cliramesiis icorice, one sex, usually the male, backs into the 

 entrance-hole, and, dying in this position, helps to guard the larvie from 

 such enemies as might wish to enter the burrow. 



In those species which lay the eggs in masses along tlie sides of the 

 primary-tunnel, the larvae burrow in congress through the bark, forming 

 irregular cavities extending laterally from the primary-tunnel. 



When the eggs are laid in niches the larvae burrow separately through 

 the bark or between the bark and the wood, at right angles to the primary- 

 tunnels ; these side tunnels, larval galleries or mines thus formed increase 

 in size as the larvae grow, and are left completely filled with wood or bark 

 fragments which have passed through the body of the larvs. The latter 

 feed entirely upon bark or wood. 



If the direction first assumed by the larva; is not parallel with the 

 wood-fibres, the larval-mines are usually found to turn, tending to follow 

 the direction of the fibres. The larvae at and near the ends of the 

 primary-tunnel swing around almost immediately, while those nearer the 

 middle do so as rapidly as is possible without encroaching upon the mines 

 of their neighbours. Usually the larv?e keep carefully to their own pre- 

 serves, only crossing a neighbour's gallery when necessity compels them 

 to do so. When the larval mines are entirely in the bark their direction 

 has no definite relation to that of the wood fibres. 



After the larval development has been jussed, varying in length with 

 the species, the ends of the larval mines are enlarged and sometimes 

 driven down into the wood to form the pupal chamber. In some species 

 the pupal period lasts but a week or ten days, in others the winter is 

 passed in this condition. After transformation is completed, the young 

 adults cut their way out tinough the bark, forming die openings known 

 as " shot-holes." 



While the primary-tunnel and also the egg-niches are usually deeply 

 engraved in the wood, the larval-mines are often entirely in the bark, or 

 only cut the wood at the pupil-chambers. On Ash trunks, where the 

 bark is thick, the larval-mines of Ifylesinus aculeatus but slightly engrave 

 the wood surface, while on small branches, where the bark is thin, the 

 mines ufica cut the woorl as deeply as they do tiie bark. 



