GALL APHIDS OF THE ELM. I99 



excretion, and with the various-sized globules of gummy liquid, which 

 IS sometimes so abundant that it will fall upon the ground like a sr.ower 

 of milky fluid, whenever badly infested trees are shaken. The insects 

 comprising this second generation, or the immediate issue from the ?tem- 

 mother, thus born within the habitation which she had built up, are 

 similar to their parent but somewhat larger at the moment of birth 

 than she was, and of a paler olive-green color. They are quite active 

 within the gall, exploring its concavities, and obtaining their nourish- 

 ment through its walls. After the second molt, they attain the pupa 

 state, (Fig. 129, d), and in due time become winged. There is but one 

 generation produced within the gall — a generation, however, that be- 

 comes very numerous under favorable conditions. They all become 

 winged, and in this respect the species differs essentially irom Schlzon- 

 eura americana as we have already seen. The winged lice carry their 

 wings flat on the back while in the gall, but deflexed afterward. They 

 issue from the slit on the lower surface of the leaf, which opens for 

 their exit about the time they become fledged. They are all females, 

 and give birth, in the course of a day or so, to upward of a dozen young, 

 which, when first born, are enclosed in the usual delicate egg-like cover- 

 ing already alluded to, and which look like their immediate parent at a 

 corresponding state of existence, except that their antennae have five 

 subequal joints, and the promuscis reaches to the hind coxae (Fig. 

 129, c). 



"So far I have been able to trace the history of the species with abso- 

 lute certainty, watching it for several years, and proving, by extracting 

 the stem-mother soon after she had commenced reproducing, that the 

 second generation, i. e., her immediate progeny, all become winged, the 

 species agreeing in this respect with the gall-making species of Phyllox 

 era that affect the Hickory. There is, however, a link yet wanting m our 

 knowledge of the history of this species, between this third generation 

 and the mouthless sexual individuals, the females of which so often 

 perish while yet covering their solitary winter eggs. I have not been 

 able to prove absolutely that there are two broods of the gall-making 

 female, and my observations all tend to the conclusion that no galls are 

 formed except by the stem-mother that hatches from the impregnated 

 egg. I have never succeeded in obtaining galls either by enclosing the 

 winged females in muslin bags tied on the living trees, or by similarly 

 enclosing her immediate progeny, though I have succeeded in obtaming, 

 without any difficulty, an abundance of galls by so enclosing the stem- 

 mother. Moreover, all such succulent galls as th*s one are produced 

 on the tender young leaves only, and I have failed to find them on any 

 but those which develop early in the season. It is true that we may 

 frequently find the galls quite fresh, and containing larvae, pupae, and 

 winged insects as late as the first week in July, and these late gallt-, as 

 well as the insects within them, are generally more yellowish than those 

 found earlier in the year; but a careful study of the structure of the 

 inmates shows them to be identical with those found in the earlier galls, 

 and these late galls are, from present knowledge, to be attributed to the 

 work of late hatching and late developing stem-mothers rather than to 



