106 HYMENOPTERA. 



This family includes the true gall-flies, a very large number of 

 which are attached to the oak, and a few to other trees. They 

 are, however, not the only gall-insects ; for the family of gall-gnats 

 amongthe Diptc7^a (Cecidoonyiidcc) ,SiudseveYalotheT s\iec\eshe\orig- 

 ing to various Orders, are likewise gall-producers. The Cynipidce 

 are small insects (sometimes exceedingly minute), and are generally 

 provided with large wings, though some of the alternate broods 

 (formerly placed in the genus Biorhiza, Westw.) are apterous. 

 The oak-galls are very various in shape and size, the so-called oak- 

 apples, produced by Aphilothrix Badicis, Fabr., and Teras Terminalis, 

 Fabr., are large and soft ; the gall of Dryophanta Scutellaris, Hart., 

 placed on the under side of a leaf, is about the size and shape of a 

 White Heart Cherry, and hard ; and the Artichoke Gall, produced 

 by Ajjhilothrix Fecundatrix, Hart., really resembles an artichoke in 

 miniature, or, more exactly, a small green fir-cone. The gall-nuts 

 of commerce, from which ink is obtained, are produced by an 

 exotic species of Cynips, as are also the so-called apples of Sodom, 

 which are met with in the neighbourhood of the Dead Sea. Very 

 dissimilar from any of these is the mossy excrescence called the 

 bedeguar, which is common on the wild rose, and is the gall of 

 Rhodites Eosce, Linn. 



The Cynipidce present problems of great interest. For a long 

 time it was believed that no males of many species existed, and 

 that the race consisted wholly of fertile females. One great 

 difficulty in investigating these insects is that the galls are so 

 greatly infested by parasites, chiefly belonging to the family 

 Chalcididce, that the parasites bred from the galls often far out- 

 number the real owners. At length, however, it has been 

 ascertained that a large number of the gall-producing Cynipidce, if 

 not all, are dimorphous, and exhibit a regular alternation of genera- 

 tions, the spring and autumn broods being so utterly diff'erent 

 that they were hitherto always supposed to belong to different 

 genera. The spring broods consist wholly of fertile females, 

 and the autumn broods consist of males and females. In some 

 cases the former are apterous, and live at the roots of trees ; and 

 the galls from which the spring and autumn broods proceed 

 are as diff'erent as the insects themselves. Thus, according to 

 Adler, Neuroterus Fumipennis, Hart., a small black insect with 

 reddish legs and clouded wings, which appears in May, and is 

 produced from a round flat scale-like gall on the under side of 

 the oak leaves, is the female parthenogenetic form of Sp)athegaster 



