108 



THE AMERICAN ENTOMOLOGIST. 



[Fig. 88.] 



Color— Black. 



It makes its appearance in the winged state in 

 September, and early in the folloTring sum- 

 mer the g-reen and sliining hollow gall, with its 

 skin as thin as that of a capsicum, may be dis- 

 covered almost full gi-own upon cottonwoods, 

 and occasionally upon balsam poplars. At this 

 period there is alwaj's found a single wingless 

 riant-louse inside it, which has by her sole ex- 

 ertions caused the growth of the gall, and which 

 will subsequently give birth inside it to a very 

 large and flourishing family of young Plant- 

 lice, all of which will eventually acquire wings 

 and leave the gall in the ensning September. 



The Sumac-gall (Ehois, Fitch), Fig. 89.— 

 This tomato-like gall occurs on the leaves both of 

 the Smooth Sumac (BMts glabra) and the Stag- 

 horn Sumac (Bhus typhina), and in the States 

 both of Illinois and New York. Like the preced- 

 ing, its shell or skin is quite thin, and the 

 winged flies are found inside it in prodigious 



[Fig. 89.] 



Color— Greenish yellow, with a ro.9y cheek. 



numbers in September. Early in the spring, as 

 we have been informed by Dr. Wm. Manlius 

 Smith", of Manlius, N. Y., each gall contains but 

 a single wingless mother-louse in company 

 with numerous larvffi. The winged fly has the 

 veins of its wings ari'anged in the same pattern 

 as those of the preceding species (Fig. 88), but 

 diflers in having four-jointed instead of six- 

 jointed antennro. It is also a very much smaller 

 insect. 



It is remarkable that there are two Chinese, 

 one Japanese, and one Indian gall, growing 

 upon different species of exotic Sumacs, and ap- 

 parently analogous in their structure to our 

 American Sumac-gall. They are described as 



being, some of them like a radish-pod, some 

 like an ox-horn and over two inches long, and 

 some branched like a stag's horn. One of these 

 Chinese Sumac-galls, which is not uncommonly 

 to be met with in drug stores, is shaped much 

 like ours, but has a much tougher and thicker 

 rind. On breaking a specimen open, we found 

 it to be filled with infinite numbers of plant lice, 

 having wings exactly like those of our insect, 

 being of the very same size, and apparently be- 

 longing to the very same genus. Thus we see, 

 that even on the opposite sides of the globe, 

 analogous galls are made on analogous plants by 

 analogoiis insects.* 



The CocKscojre Elm-gall {Ulmicola, Fitch), 

 Fig. 90. — This species has a much tliicker and 

 more fleshy rind than the two preceding. 

 Young Wliite Elms often have their leaves so 

 densely covered by these galls that you can 

 scarcel}- see the leaf for the galls. After trees 



[Fig. 90.] 



/■ 



( loi— Cii LI ft n^^ tl ml 1 o 1 



get to be about t■\^enlJ-fi\e Icet high the gall- 

 making insect ceases to trouble them ; and the 

 younger the 'trees the more apt they are to be 

 infested. The Plant-louse that produces these 

 galls is exceedingly minute, and differs in the 

 veining of its wings from figure 70, c, (p. 82), in 

 the hind wing having but a single branch vein, 

 the front wings corresponding in every respect. 

 It is, however, remarkable for holding its wings, 

 when in repose, horizontally on its back, instead 

 of carrying them steeply roofed, as is the case 

 with almost all the other genera of Plant-lice. 

 Early in the spring but a single wingles.s mother- 

 louse is to bo found in a single gall ; but in a 

 short time she gives birth to hundreds of very 

 minute and wingless young larva?. By the 

 end of June or the beginning of July, the 

 gall becomes full of winged plant lice, when the 

 slit on the under side of the leaf, through which 

 the mother plant-louse built up the gall early in 



• For further details on this subject see Proc. Ent. Soc, 

 Phil., VI., pp. 28T-2, notes. 



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