ZooL— Vol. III.] KELLOGG— NET-WINGED MIDGES. 207 



Altogether the difference between the mouth-parts of 

 Blefharocera and the typical biting type is one of modifica- 

 tion, and of modification not sufficient to obscure the 

 homologies, although a modification more profound than 

 that shown by the most generalized Lepidoptera or Hymen- 

 optera. On the other hand, there is not much difficulty in 

 tracing the development of the dipterous mouth from the 

 generalized condition of Blefharocera (or Simidium, or 

 Dixa, et al.) to that extraordinary speciahzed condition 

 shown by Musca, where the mandibles and maxillse are 

 lost, and the labium is so modified that it has no longer any 

 likeness to the 'lower lip' of the orthopterous mouth," 



Although it has seemed from a comparative study of the 

 imaginal mouth-parts of all the nematocerous (generalized) 

 families of Diptera (excepting the Ornephilidae) and of 

 most of the brachycerous (specialized) families, that the 

 homologies of the mouth-parts can be satisfactorily deter- 

 mined, certain entomologists have refused to recognize the 

 determination of homologies thus based to be conclusive. 

 With this in mind, and recognizing, indeed, the general 

 desirability of testing by ontogenetic study any conclusions 

 arrived at from comparative anatomical study, the writer 

 has studied the post-embryonal development of the mouth- 

 parts of representatives of two of the nematocerous 

 families of Diptera, the Simulid^ and Blepharocerid^e, 

 whose females are equipped with what are here said to be 

 all the recognized parts of the generalized orthopterous, or 

 typical biting mouth. These parts are indeed much 

 modified, the mandibles in particular being oddly elongated 

 and serrated to form a pair of rasping knives, or saws, with 

 which the body of the prey (smaller insects, especially 

 Chironomids) is lacerated so that the blood and body juices 

 may be sucked. 



In this study, the results of which are published elsewhere 

 in connection with studies of the development of the imaginal 

 mouth-parts of other orders of insects with complete meta- 

 morphosis (Kellogg, 1902), it has been possible to trace the 

 development of the imaginal parts within the head of the 



