28 



beetle was then blockadetl by a l)it of bmk in a brancli of the burrow, and for 

 each sufficient space was left for air and the discharge of frass. A week after 

 each beetle had eaten a narrower burrow just long enough to hold it, merely to 

 sustain Ufe, contrasting with the wider burrow outside, but no more eggs had 

 been laid. 



The eggs are laid along both sides of the burrows, usually at very regular 

 intervals, in little hollows dug out to receive them, leaving the gallery of full 

 size for the beetles within it. They are covered vrith a gummy material, which 

 soon gets a coating of the finer frass. These eggs being laid in rotation, form a 

 good series for observing the development of the larvas within the egg, the first 

 being often hatched and the young grub boring into the bark before the last ia 

 laid. Their longest axis is perpendicular to the surface, and the young larvae 

 are developed within the eggs with their heads toward it. The eggs 

 laid in one burrow vary from 15 to 40 or 50, or even 60 to 100. The 

 gallei-y is finished and the eggs laid in from ten to twenty days. During 

 the ejection of the frass, particles adhere by a gummy matter, and form an 

 operculum to the mouth of the burrow, leaving only a minute opening for frass, 

 which on the completion of the burrow is stopped up. Both beetles then usually 

 die in the buiTow ; the female always does so. The dead beetles may still be 

 found lying in the burrows after several years. 



During the summer the larvce are busily feeding in the bark. They are 

 straight, white, footless, fleshy grubs, with a distinct head and powerful 

 mandibles. In some of my specimens they are already (May 22) hatched. In the 

 autumn they assume the pupa state, and shortly the imago. The perfect beetles, 

 however, usually remain during the winter at the ends of the buiTows formed 

 by the larva?, and emerge in spring to continue their ravages, leaving a very 

 distinct circular aperture ; on a sculptured piece of bark all the very obvious 

 holes are apertures of exit, those of entry being very obscure. 



It often happens that the parent beetles have made theii- biu-rows so close 

 together that the supply of bark is quite inadequate to the wants of the larvas, 

 so that their very abundance is its own remedy, and most of them perish. In 

 other instances the vitality of the bark ceases before the larvse are fuU fed, the 

 tree having fallen too long when attacked, so that but a small proportion 

 usually comes to maturity. 



I have remarked the preference of this species (Hylesinus Fraxini) for 

 fallen timber, nevertheless they do occur on living trees. On almost any young 

 ash tree marks may be found shewing that a burrow had been formed and a 

 brood of Hylesinus Fraxini perfected, and that the tree is now exfoliating the 

 destroyed bark. Sometimes I think the growth and vigom- of the trees appear 

 to have been decidedly checked by them ; and though I have not met with an 

 example, I doubt not that trees are occasionally killed by this beetle. In other 

 instances trees with these marks appear to be uninjured. Where they are 

 injurious they may be extirpated by cutting down affected trees, stripping off 



