Walter Ritchie 333 



age it was a common occurrence to find the horizontal portions of the 

 larval galleries running into each other, with the result that the stems 

 were completely ringed. After the larvae had completed this portion of 

 their galleries, they would turn downwards in the stem, completing their 

 tunnels in one of the ways already described. 



As a general rule, on very badly infested stems and where these had 

 already been badly holed by larval tunnels, the younger larvae would 

 tunnel in any direction where the wood was intact and make no pro- 

 vision for the exit of the imagines, leaving these to escape through old 

 flight holes. 



In exceptional cases, on badly tunnelled stems, the adults cut their 

 own flight holes, choosing a part of the stem where the outer bark was 

 fissured or where it was thin. 



The Habits of the Larva in the Stem. 



The manner in which the larva propels itself in the stem during 

 feeding and the cutting of the gallery is very interesting, as apparently 

 it can ascend or descend with equal facility. The grubs are legless, but 

 locomotion is secured through the use of well developed dorsal and 

 ventral ambulatory ampullae, which come into play either from the 

 anterior or posterior end of the body in peristaltic succession. These 

 ampullae, together with the chitinous asperities on the dorsal surface of 

 the prothorax, braced against the sides of the gallery, constitute an 

 efficient and rapid means of locomotion. In descending the stem the 

 various movements may be reversed, but most commonly the larva 

 descends head in front. 



During the gnawing process the head and thorax are moved with a 

 side wise motion, and in this way the wood is bitten off. Some of this 

 gnawed material is passed through the alimentary canal, but by far the 

 most of the material is passed behind into the gallery, and is either 

 pushed to the outside of the stem through an egg-incision or exit hole, 

 or is pressed tightly to the sides of parts of the gallery. 



The young larvae when present in large numbers in a stem develop 

 a cannibalistic habit, and often one finds on tracing the galleries in such 

 stems, that some of them end very abruptly. If, experimentally, a few 

 larvae of different sizes be placed together in a box for a short time, say 

 for an hour, the smaller ones on being examined at the end of this period 

 will be found to have been badly bitten by the larger ones, and they 

 subsequently die. 



Ann. Biol, vn 22 



