Feb. 3, 1920 



European Frit Fly in North America 



455 



only finn structures are the two mouth hooks and the frame to which 

 they are attached. The hooks are clear reddish brown in color. The 

 frame is black at their attachment and becomes gradually less chitinized 

 and paler farther back, and more concealed by the mass of muscles 

 surrounding it. Figure 3 shows one-half of this double structure. The 

 hooks work on a pivot at the point marked x in the figure. The larva 

 has 1 1 segments, the sutures between them, except the first three, bear- 

 ing transverse rows of very fine teeth below, which extend up the sides 

 in a narrowing series. The first seg- 

 ment is encircled by several rows of 

 these minute teeth, evidently of use in 

 entering crevices. At this stage there 

 appear to be no anterior spiracles, the 

 only ones being a pair at the posterior 

 end; these are on raised protuberances bearing a circle of branched 

 hairs standing at right angles to the axis, the opening into the air tube 

 being on the inner side, not the tip, of the protuberance. From each 

 spiracle a conspicuous air tube extends forward along the side of the 

 body. 



FULL-GROWN LARVA 



Fig. 2. — Egg of Oscinis fril. X 65. 



The full-grown larva (fig. 4) measures about 3 mm, in length and 0.4 

 mm. in greatest diameter. It is distinctly yellow in color on account of 

 the accumulation of fat under the integument, for use during transforma- 

 tion. The antennae and mouth hooks (fig. 5)) are relatively smaller than 



Fig. 3. — Newly hatched larva of Oscinis frit. X6s. Antenna and mouth-hooks more enlarged, the latter 

 showing fulcrum at x. 



in the first stage. The mouth hooks are strongly curved, black, with 

 several microscopic teeth on the under side. Anterior spiracles occur 

 on the first segment, consisting of a protuberance bearing a half dozen 

 soft lobes in a vertical row. The posterior spiracles appear to occupy a 

 median position on their protuberances, with less distinct circles of hairs. 

 Intermediate larval stages were not made out. 



PUPA 



Like many Diptera, this species forms the pupa within the hardened 

 larval integument, called the puparium. The pupa is never visible unless 

 this shell-like covering is removed. It is white at first, becoming black 



