PROCEEDINGS. 



curious that the shreds and nails used in fastening the 

 branches to the wall are also embedded in the solid growth 

 of the tubercles. Out of the mass has grown a number of 

 two-year old shoots, none of which are more than 1§ inch 

 long, and at the tips of these are to be seen the buds of the 

 present year, which have never grown beyond the size of 

 buds ; in fact, the natural growth of the tree has, in this 

 part at least, been entirely interrupted, and the whole power 

 and energy thrown into the elaboration and growth of tuber- 

 cular masses of wood. The agent which has produced this 

 disease is a species of aphid nearly allied to the American 

 blight of the Apple. At the present time the tubercles and 

 adjacent part of the stem are clothed with a fine grey powder, 

 and the former are thickly studded with minute white par- 

 ticles, which are the cast-off skins of innumerable aphids, 

 which are of a very small size, and are seen crawling about 

 the knobs. In the absence of the winged states of the insect 

 we shall abstain from giving a technical description of the 

 species, which may be named Eriosoma pyri. The small 

 wingless individuals are greyish black, with white woolly 

 matter exuding from the hind part of the body, the antennae 

 six-jointed, with a very small appendage or joint at the tip 

 of the sixth joint, and the tarsi are two-jointed and termi- 

 nated by two claws. The size of the largest of the indi- 

 viduals we have met with is shown near the * in our 

 woodcut. For the size of the insects the proboscis is re- 

 markably strong, being at least twice as thick as the legs or 

 antennae ; and it is this instrument which lias produced all 

 the disorganization which we have described. It would lead 

 us into a wide field to inquire into the effects produced on 

 different kinds of plants by the punctures of insects, effected 

 either by the proboscis, for their own food, or by the ovi- 

 positor, for the establishment of a situation for the safe 

 deposition of the eggs. The question also involves the fact 

 whether the growth of these and similar tubercles or galls 

 is produced partially or entirely by the introduction of 

 some irritating fluid discharged by the insect into the 

 wound, or simply by the effect of the wound itself. How 

 far too the state of the plant at the period of the infliction 

 of the wound may tend to the greater or less development 

 of these galls, is also to be determined ; at all events it is 

 perhaps certain that, under all circumstances, the attacks of 

 this particular kind of aphid, upon any kind of Pear-tree, 

 would result in the formation of galls of a larger or smaller 

 size, in which case we may perhaps be correct in considering 

 this aphid as a new importation, as dangerous as the Ame- 



