HYMENOPTERA. 395 



The four-winged gall-flies have very little outward resemblance 

 to the saw-flies and horn-tailed wood-wasps. They agree with 

 them, however ,-in boring into plants, and iti laying their eggs there- 

 in. Vegetation does not often suffer much injury from their attacks, 

 and it is only on account of the very singular productions, called 

 galls, arising from the irritating punctures of these insects, that 

 the attention of cultivators is at all likely to be drawn to them. 

 There are some two-winged flies, and also some other insects, 

 which produce various kinds of excrescences or galls on plants ; 

 but these, now under consideration, are very small, four-winged 

 insects, belonging to the order Hymenoptera, and distinguished 

 by the following peculiarities. The head is small ; the antennae 

 are rather short, slender, and thread-like ; and the thorax is thick 

 and hunched. The abdomen or hind-body, viewed sidewise, ap- 

 pears round or oval, but it is sharp-edged above and below, 

 very thin or pinched up at the sides, and is hung to the thopax by 

 a very short and slender stem. The fore-wings are rather long, 

 and have only a few veins in them ; the hind-wings are small, and 

 seemingly veinless. The borer of the females is very long, and 

 slender, concealed in the under-side of the hind-body, the curva- 

 ture whereof it follows, and is capable of being straightened and 

 thrust out of a narrow chink, which is covered by two little, 

 grooved, sheath-like pieces, that serve to conduct the eggs into 

 the holes made with the instrument. The genus containing most 

 of the gall-flies was called, by GeofFroy, Diplolepis, that is, 

 double scales, on account of the two pieces that cover the open- 

 ing for the borer in the hinder part of the abdomen. The same 

 insects, however, had previously been placed by Linnaeus in the 

 genus Ci/nips^ so called from a word used by ancient authors to 

 designate some small ])ier€ing insect. The Linnsean name, though 

 for some time rejected, has been restored to the gall-flies, which 

 accordingly are now included in a family called Cynipid^. The 

 punctures, made by these insects in the leaves, buds, stems, and 

 roots of plants, are followed by swellings of the wounded parts, 

 which increase rapidly in size, and become spongy or pulpy with- 

 in. The thin-skinned eggs, dropped into the punctures, grow 

 awhile, by absorbing the sap around them, and, when at length 

 they are hatched, the little grubs, proceeding therefrom, find 



