36 STKUCTUEE OF CERTAIN DIPTEROUS LARV^. 



the body is slightly constricted in the middle, with a basal roughened 

 area encircling each segment; anal tubercle broad, dark colored, 

 bilobed, but not very prominent; around tip of body are several 

 pairs of tubercles; five pairs are described for D. ampelopMla Loew, 

 four pairs for D. amosna Loew; the stigmal plates are on the tips of 

 two approximate cylindrical processes which rest on an elevated 

 part of the tip of the body. 



The pupae are rather barrel-shaped, with a slender projection at 

 each anterior corner of the body, the process varying in size and 

 tubercles with the species; the posterior end of the body is provided 

 with tubercles similar to those of the larvae, and stigmal plates at 

 the tip of a pair of truncate projections. The pupse are usually 

 found in the same lot as the larvae, as evidently but a few days are 

 required for them to develop from the eggs. 



Drosophila larvae and pupae are quite common in overripe fruit, 

 especially grapes, pears, and apples; they also occur in jellies, jams, 

 vinegar, pickles, etc., and so are frequently swallowed by people. 



THE CEPHALOPHARYNGEAL SKELETON. 



The structure of the cephalopharyngeal skeleton varies with the 

 species. It is not always feasible to use this structure in identifying 

 material, since it usually necessitates the destruction of the anterior 

 part of the larva, which one does not care to do in unique specimens. 

 Figures have been given of this skeleton as seen in several species; 

 but it can not be used as a diagnostic character for groups until one 

 has examined a larger number of species. In the first larval stage 

 this skeleton is formed of very slender pieces, only narrowly con- 

 nected, but in the second and third stages the parts broaden, espe- 

 cially the lateral plates. 



In the Trypetidae (figs. 125, 132) the lateral plates are only weakly 

 chitinized, and not black; they are deeply indented from behind, so 

 that the upper and lower limbs are connected only for a short dis- 

 tance. The great hooks have a very prominent spur above at base. 



In the Ortalidae (Euxesta, fig. 121) the skeleton is very similar 

 to that of the Trypetidae. 



In the three species of Sarcophaga examined the lateral plates are 

 not so deeply indented from behind, and the upper limb shows a 

 slender appendage along its lower edge; the great hooks have a spur 

 above at base (fig. 134). 



In the Muscidae (figs. 115, 120) the lateral plates are still less 

 indented from behind, the lower limb being much larger than the 

 upper limb; the hypostomal sclerites are short and heavy; the great 

 hook (for there is but one) has a rather small spur above at base. 



In the Calliphorinae (figs. 126, 128, 131) the lateral plates are 

 deeply indented from behind, and here it is the upper limb that is 



