1910] Anatomy of Cecidomyia resinicoloides 47 



nected with any muscles. Owing to the medium in which the 

 larva lives, it is possible that it has lost this power of leaping by 

 the degeneration of the organs so well developed in the saltatorial 

 Cecidomyid larvae. Locomotion in the larva of C. resinicoloides 

 is chiefly, if not wholly, accomplished by the extension and con- 

 traction of its spiny segments, with the possible assistance of the 

 pseudopod-like processes. 



Another theory advanced to explain the use of the breastbone 

 is that it is used as a perforator (17). It could thus be used in 

 some gall-forming species which pupate outside their gall, to 

 force an exit therefrom. L. O. Howard (11) refers to a view pro- 

 posed by Enock and sustained by Marchal according to which 

 the spatula is used to reverse the position of the larva in the 

 puparium. In the case of C. resinicoloides this last theory might 

 apply, but it seems more probable that the spatula is used in 

 making the cocoon, in pushing out a space in the resin, and form- 

 ing the thin, convex cocoon cap. Inasmuch as, according to 

 Giard, the spatula is only fully developed in the last moult, it is 

 quite evident that this organ is intimately associated with the 

 prepupal actions of the larva. Osten Sacken says (14) : "If the 

 supplementary (14th) segment be considered as a part of the head, 

 this breastbone might be taken for the mentum, in analogy to the 

 horny mentum of the larvae of the Tipulariae." 



Pseudopods. These are rounded, somewhat nipple-like pro- 

 cesses, most prominent on the thoracic segments and usually in 

 double pairs on the segments. Segment I has a pair on each 

 anterior side of the spatula and bordered anteriorly by the 

 imaginal leg discs ; segments 2 and 3 have each a more prominent 

 double pair, transversely arranged in the middle of the segments 

 and likewise bordered anteriorly by the leg discs, those of the 

 wings being lateral ; segment 4 has an inconspicuous pair of pseu- 

 dopods; segment 10 some indistinct protuberances; while on 

 segment 1 1 are a pair of rather widely separated protuberances 

 anterior to the anal slit. The last or 12th segment is terminated 

 by two conical projections bearing a bristle at their apices. 



Spiracles. There are nine pairs of spiracles, normally situated, 

 one on the first thoracic segment and one each on segments 4-1 1. 

 The last pair is placed apparently on the last segment, but Osten 

 Sacken (14) has pointed out that this segment is in reality the 

 8th abdominal, the 9th being in C. pini and C. pini-inopis, (the 

 latter being considered a synonym of C. resinicola) unusually 



