326 



The Large Poplar Longhorn 



bark, resting mainly on her middle and hind pairs of legs, she thrusts 

 out her ovipositor, inserts it into the incision and forces an egg through 

 it. Before the ovipositor is withdrawn, a colourless gummy fluid is 

 passed into the egg-incision. During this operation much muscular effort 

 is expended, for the egg is pushed away from the egg-bite. Where the 

 bast layer is thin, e.g. on stems between five and twelve years old, the 

 egg is found firmly placed between the cambium layer and the sapwood. 

 and about 2-5 mm. from the egg-bite. On the other hand, if the stem be 



fsm 



ill i 



Fig. 22. Lower nine inches of 6-7 year old poplar stems showing egg-incisions and bur- 

 rowings of young larvae (dark patches in figure). Two eggs and the young larval 

 burrowings are here exposed by the tearing away of the bast and cambium layers. 



older and the bast layers thicker, the egg is placed between the tissues 

 of the bast. 



The spot selected by the female for egg-laying is always a smooth 

 portion of the stem. On no occasion have I found her laying eggs in 

 cracks or lenticels. I am inclined to believe that the statement in 

 continental works that eggs are laid in cracks, is due to the fact that the 

 actual egg-laying of the beetles has not been observed, the eggs having 

 only been noticed when the egg-incisions bad begun to gape, viz. in 



