CECIDOMYIA. . 179 



structure is as in most Campylomyzce. The number of the joints 

 of the antennae being of a higher value, among the Gall-gnats, for 

 the distinction of species than for that of genera, since almost 

 every genus comprises species with very different numbers of joints 

 of the antennas, I abstain from giving a name to the species known 

 to me so incompletely ; as to the genus, which can never be mis- 

 taken, I propose for it the name of Tritozyga." 



II. On the habits of the CECIDOMYID^E. 



The food of the larvas of Cecidomyia is of a vegetable character. 

 A few apparent exceptions will be mentioned below. They 

 furthermore seem to live in preference on living plants; neverthe- 

 less several species of the subgenera Epidosis and Diplosis, have 

 been reared by Mr. Winnertz from decaying wood ; Cec. fuscicollis 

 Meig. (?) has been reared by Bouche from decaying bulbs of tulips 

 and hyacinths. (Instances like that of Cec. bicolor Bouche, found 

 in dung during winter, must be received with caution, as the larvae 

 may have gone there for transformation only.) Although the 

 majority of these larvae attack the soft and green parts of plants, 

 some of them live under the bark of trees, in the cones of pines 

 (Cec. strobi Kalt.) or in fungi (Diplosis polypori Wz., Asynapta 

 lugubris Wz., etc.) 



Again, most of the larvae are monophagous, that is, each species 

 lives exclusively on a certain species of plant, or, at least on closely 

 allied plants; Mr. Winnertz remarks that even those found under 

 the bark of trees follow the same rule. Exceptions are Cec. 

 sisymbrii Schr., which, according to Mr. Winnertz, inhabits in 

 May and June a gall on Berberis vulgaris, and from June till No- 

 vember a somewhat different gall on Nasturtium sylvestre (Winn. 

 1. c. p. 209 and 231) ; Cecid. arcuata Wz., has been found in the 

 pappus of different syngenesists, in decaying wood and fungi. 

 Besides these, there is a class of larvae which live as guests or 

 parasites in galls formed by other Cecidomyia {Cec. acrophila Wz. 

 and pavida Wz. live socially in the deformed buds of Fraxinus 

 excelsior; Diplosis socialis Wz. inhabits the gall of Lasioptera 

 rubi ; Dipl. tibialis Wz. , has been reared from the same gall with 

 Cec. salicina Schr., etc.); or by Acari (Cec. peregrina Wz., and 

 similar cases, observed by Loew.) Some even live in the society 

 of Aphides. According to Mr. Winnertz the larvae of the sub- 

 genus Diplosis principally, share these parasitical habits ; even 



