. A treatise on some of the insects injurious to vegetation . Insect pests. 546 HYMENOPTERA. icine, are caused by the punctures of the Cyrdps gaEm tinctorice on a kind of oak growing in the western part of Asia; insect may often be found in those which are not pierced with holes. Some galls contain only a single insect, lodged in a little cavity in the centre; other kinds are inhabited by several grubs, each in a cell by itself, and the cells not unfrequently resemble numerous small seeds, clustered together in the middle of a fruit. Two or three different kinds of insects are often fo
. A treatise on some of the insects injurious to vegetation . Insect pests. 546 HYMENOPTERA. icine, are caused by the punctures of the Cyrdps gaEm tinctorice on a kind of oak growing in the western part of Asia; insect may often be found in those which are not pierced with holes. Some galls contain only a single insect, lodged in a little cavity in the centre; other kinds are inhabited by several grubs, each in a cell by itself, and the cells not unfrequently resemble numerous small seeds, clustered together in the middle of a fruit. Two or three different kinds of insects are often found to come from one gall, namely, a few gall-flies, which are the lawful proprietors thereof, and more numerous four- winged flies (), with elbowed- antennas. The latter are bred from grubs, which devour the grubs of some of the gall-flies, or starve them by eating up their food, and thereby contribute to check the too great increase of the gall-flies. The largest galls found in this country are commonly called oak-apples. They grow on the leaves of the red oak, are round and smooth, and measure from an inch and a half to two inches in diameter. This kind of gall (Plate VIII. Fig. 9) is green and somewhat pulpy at first, but when ripe it consists of a thin and brittle shell, of a dirty drab color, enclosing a quantity of brown spongy matter, in the middle of which is a woody kernel about as big as a pea. A single grub (Fig 253, magnified) lives in the kernel, becomes a chrysalis (Fig. 254) in the autumn, when the oak-apple falls from the tree, changes to a fly in the spring, and makes its escape out of a small round hole which it gnaws through the kernel and shell. This is probably the usual course, but I have known this gall-fly to come out in Octo- ber. The name of this insect is Cyrdps confluens.* (Plate * Diplolepis cohflwnttis of my Catalogue, and so named by Mr. Say. Fig. 253 Fig. I. Please note that these images are extracted from scanned page images th
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