GALL APHIDS OF THE ELM. 225 



brownish tint. In general appearance, they resemble the young from 

 the stem-mother. The beak is very long, thickened at the end, which 

 always projects beyond the tip of the abdomen, and terminates in a fickle- 

 like point. Experiments made by attaching and confining these young 

 to the trunk of the tree show that they do not flourish thereon, but nat- 

 urally crawl out to the more tender, terminal leaves, which they imme- 

 diately begin to curl. They may be found scattered over an infested 

 tree, with their beaks for the most part inserted in the tender leaf-stem 

 or in the midrib on the under side, the leaf in such case already begin- 

 ning to show the effect of the poisonous puncture. They are, however, 

 able to sustain themselves on the tender bark of twigs alone, and may 

 be found nearly fully-grown, there exposed to view and enveloped in the 

 white cottony matter, which brushes off at the slightest touch. When 

 full-grown, they commence reproducing, and their progeny, under favor- 

 able circumstances, becomes exceedingly abundant. The growing points 

 of the tree are affected with larger or smaller colonies, crowding and 

 covering both the surfaces of the leaves, the petioles, and the stem. I 

 have known young Elm trees to be so thoroughly covered with these 

 lice, in the earlier part of June, that not a single leaf was unaffected, and 

 upon giving the tree the sligh'test jar there would be a perfect sliower 

 of the liquid globules excreted by the lice. At this season of the year, 

 when the lice are thus numerous, they may be found during the heat 

 of the day actively crawling over all portions of the tree — a veritable 

 migration, necessitated by the want of sufficient succulent leaves, but 

 evidently premature and destined to be the death of the individuals par- 

 ticipating in it, excessive multiplication here, as in all other cases, obliging 

 the destruction of the excess. While the individuals thus wandering are 

 mostly the younger ones, the migrating instinct seems sometimes to 

 possess individuals of all ages, especially where the tree is badly aft'ected ; 

 and that they perish is proved by the mass of dead lice which in such a 

 case may be found around the base of a tree. So far as I have been able 

 to learn by confining specimens of the fiftli generation, which is very 

 similar to the fourth, but with shorter pronuiscis. the fifth reproduces 

 like the fourth without acquiring wings. The individuals of the sixth 

 generation, on the contrary, all acquire wings, the pupa being active, with 

 but a small amount of flocculence, confined to the posterior part of the 

 body. The winged lice of this sixth generation abound during the 

 latter part of June and the early part of July. They resemble those 

 of the third generation, except that they are perhaps on the avr;rage 

 somewhat smaller and paler, and less prolific. They instinctively con- 

 gregate on the bark, and consign to the crevices, and sheltered parts 

 thereof, their young, which, as in the fourth generation, are enveloped 

 in a sort of pellicle. These young also resemble the young of the fourth 

 generation in general form, but have very short and stout beaks. Instead 

 of being active, they are quite sluggish, congregating in clusters in the 

 sheltered portions of the bark, and being essentially bark-feeders. The 

 color soon inclines strongly to sahr.on or orange, and, after two or three 

 days of sluggish existence, they shed their skin, and become more ac- 



