THE ANATOMY OF THE LARVA OF CECIDOMYIA 

 RESINICOLOIDES WILLIAMS. 



By Francis X. Williams. 



In the January number of Entomological News, Vol. XX, i-8, 

 1909, I described this midge in its egg, mature larval, pupal and 

 imaginal instars, and gave a brief biological report on it. The 

 curious habit of the larva in living in a mass of exuding resin 

 might be expected to have brought about some adaptive modi- 

 fications of its structure, especially perhaps of its tracheal system. 

 It is for this reason particularh^ that the attempt has been made 

 to study the larval structure in detail. As much of the anatomy 

 of the larva is described here as could be worked out in a limited 

 time, and although o\'er a hundred larvae were examined and 

 dissected, the results are far from complete. Considerable diffi- 

 culty was encountered in tracing out the various systems of the 

 larva, and the writer has deemed it best to omit the doubtful 

 things and to declare only those facts which were made manifest 

 over and over again by the examination of a large number of 

 specimens. 



The work embodied in this paper was done in the entomological 

 laboratory of Stanford University. 



EXTERNAL ANATOMY OF THE LARVA .- 



Head, PI. I, Figs, i and 2. The head is very small and 

 imperfectly developed. Its brownish-black chitinized portion 

 consists of a broad irregular ring from which a pair of prong-like 

 rods project well into the supernumerary segment. These rods 

 diverge posteriorly, are more heavily chitinized than the ring, 

 and have muscles attached to them that run from the body wall. 

 The antennae are short, conical, obscurely two-jointed processes 

 placed well above the opening of the mouth. Ratzeburg and 

 L. Defour believe these processes are palpi, but Osten Sacken as 

 well as Laboulbene and Perris, from the position of these organs, 

 consider them rudimentary antennae. I incline to the latter 

 view since they are situated latero-dorsally on the anterior part 

 of the ring and well above the mouth opening. This latter con- 

 sists of a soft, fleshy swelling taken by Ratzeburg for the labium. 



Breastbone, PI. I, Fig. 3. Ventrally on the posterior half 

 of segment I, and situated in a sort of fold is the "breastbone," 



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