THE GALL FLIES. 



The Cynipidse are characterised by their iinbent antennae, which are usually thread-like, and 

 composed of from thirteen to sixteen joints, the number being frequently greater in the males than 

 in the females. The wings show no submarginal cells, except the apical one, and sometimes a very 

 small one just within the stigma, at the apex of the discoidal cell. The abdomen, which is usually 

 short, is strongly compressed, and only the first, or first and second segments, are greatly 

 developed, the remainder being retracted within these, so that only their edges project. These fully- 

 developed segments are much longer at the back than towards the ventral surface, so that the posterior 

 margins of the segments, and that of the abdomen, become very oblique, especially in the female, 

 and thus the ovipositor comes to issue from near the middle of the lower surface of the abdomen. 

 Its arrangement is very peculiar. The last visible segment is produced within the others nearly 

 to the base of the abdomen, where it has articulated to it a small triangular chitinous plate, to 

 which the sheath of the ovipositor is also movably articulated. This sheath, as in the other 

 Entomophaga, consists of two flattened joints on each side of the "ovipositor, and the apical joints 

 project from the abdomen, and, passing up along its posterior margin, produce the appearance of a 

 sort of cleft. Within this the ovipositor lies, so that its point is directed upwards. By the action 

 of muscles upon these parts, the ovipositor, which, in repose, is bent more or less in a spiral form, 

 is pushed out from between the side-pieces forming the sheath when it is being employed in egg-laying. 

 It consists, as in the Ichneumons, &c., of a principal superior piece, and two smaller pieces below, 

 the whole arranged so as to form a triangular tube, for the passage of the egg. The latter is 

 remarkable in its structure. It is considerably too large to pass easily through the narrow tube which 

 has to convey it to its destination, but it is prolonged into a narrow tubular 

 part capable of extension, and during deposition a portion of the contents 

 of the egg is forced up into this tubular part, to rejoin the main mass 

 when the process is completed. 



The number of species in this family is very considerable, although 

 in this respect it is far inferior to the parasitic families just described. 

 Of the great majority of the species, the females pierce with their ovi- 

 positor the tissues of plants and trees, and there deposit their eggs, from 

 which the larva? are soon hatched. The irritation caused by this intrusion 

 of a foreign body into the tissues 

 would seem to give rise to a morbid 

 state of the part affected, mani- 

 fested by the production of an 

 excrescence, which varies in size, 

 form, and structure, according to 

 the species of the Gall Fly pro- 

 ducing it. The insects are generally confined to one species of plant, and to a particular part 

 of it. The larva? feed in the interior of the galls, sometimes singly, sometimes several in the same 

 gall, but in the latter case each larva occupies a separate cavity. When full grown, the larvae 

 either undergo their change to the pupa state within the gall, or eat their way out, and, dropping 

 to the ground, bury themselves under the surface, and there pass through their transformations. 



The galls produced by different species differ greatly in form and structure. Some of them 

 are round and smooth like fruits, such as the cherry galls of the oak leaves, produced by the 

 puncture of Cynips quercus-folii ; others show processes, or excrescences, of various kinds, such as 

 may be seen in the well-known ink gall, the gall-nut of commerce, which is formed upon the twigs 

 of a peculiar species growing in the Levant (Quercus infectoria), in consequence of the attacks of a 

 rather large species, the Cynips tinctoria. This same oak also produces the so-called Dead Sea 

 apples, which have been often celebrated poetically. They are as large and round as a good-sized 

 apple, and each of them contains a single larva of a species described as Cynips insana. The most 

 singular of all these galls is perhaps the Bedeguar, which is formed on the stems of wild roses by 

 the puncture of a small species (Rhodites rosce). It is of considerable size, contains numerous 

 larvae, each in a separate chamber, and has its whole surface covered with compound bristles, like 

 those on the calyx of a moss-rose, so that it closely resembles a ball of moss stuck on the stem or 



INTERIOR OF GALL. OAK-GALL PRODUCED BY CYNIPS. 



