CECIDOMYIA. 181 



When first hatched, the larva is colorless, transparent, with a 

 translucent green, yellowish or red stomach; later in life it assumes 

 different shades of red (orange, pinkish, cochenille-red) or becomes 

 yellow or whitish; the color of the same species may also some- 

 what change with age. All these larvce have the extraordinary 

 number of fourteen joints, thus affording an apparent exception from 

 all other larvse of insects, which, as a general rule, have thirteen 

 joints. The supernumerary fourteenth joint is placed between the 

 head and the first thoracic (stigma-bearing) segment. It may be 

 considered either as a part of the head, or as a prolongation of 

 the first thoracic segment. Number and position of the stigmata 

 are normal ; one pair on the first thoracic segment, and eight 

 pairs on the first eight abdominal segments, so. that the ninth or 

 last segment bears none. Sometimes the last pair of stigmata is 

 removed from its usual lateral position, more towards the middle 

 of the segment. In one case (Gee. pini Deg. and the American G. 

 pini inopis) this last pair is placed apparently on the last segment; 

 but this segment is in reality the eighth, the ninth segment being 

 in this larva unusually small and concealed under the eighth. The 

 stigmata are horny, more or less nipple-shaped projections. 



The skin of most larvas appears finely chagreened under a strong 

 magnifying power; in some cases it is perfectly smooth. The 

 dorsal segments of Gee. sarothamni Lw., G. genistas Lw., etc. are 

 uneven ; those of G. craccm Lw., G. quercus Lw., G. fuscicollis 

 Bouche, etc. are furnished with bristles or sparse hairs ; those of 

 G. entomophila Pern's with hairs arranged in regular rows ; those 

 of Gecid. pini Degeer, and of two larva? which I found in this 

 country (Gee, pini inopis 0. S. and Gee. ghttinosa, nov. sp.), have 

 rows of fleshy, setiferous caruncles along the back. (It is to be 

 noticed here that both Degeer and Dufour, in describing such 

 larvas, mistook the back for the venter, and described these carun- 

 cles aspseudopods. See Deg. Mem. VI, Tab. XXVI, fig. 9 — 19, 

 and Dufour, Ann. Soc. Ent. de Fr., 1838, p. 293). 



The last abdominal segment is smooth and rounded, or furnished 

 with two setiferous tubercles (Gee. pini), sometimes uneven and 

 bristly, or excavated, or armed with a pair of horny processes, 

 frequently curved upwards. Dufour saw a larva use these pro- 

 cesses for leaping. 



The structure of the head and of the organs of the mouth is 

 bat imperfectly known. What Mr. Ratzebnrg saw (see his paper 



