January 1S99.] 



PSYCHE. 



305 



great rapidity : it is obscured by the 

 histolysis of the larval mouthparts going 

 on at the same time with the histogene- 

 'sis of the imaginal organs, and because 

 there is a marked acceleration of devel- 

 opment, by which some of the phyletic 

 stages are crowded together, or perhaps 

 crowded entirely out. So serious are 

 the difficulties in the study of the post- 

 embryonal development of insects with 

 complete metamorphosis, that, although 

 thirty-five years have elapsed since 

 Weissman's first enlightening study of 

 Musca, and although the interest and 

 importance of the study are fully recog- 

 nized by zoologists and entomologists, 

 only a scant dozen investigations have 

 been at all successfully prosecuted, and 

 our present knowledge of the subject is 

 based on five or six papers on Musca, a 

 couple of studies on Lepidoptera, one 

 on a Hymenopteron and one on a Col- 

 eopteron. Most of these papers attempt 

 to trace the development of only certain 

 organs, and in only one of the papers 

 is there an attempt to describe the de- 

 velopment of the mouthparts. Kiinckel 

 d'Herculais in 1875 discovered and 

 briefly described the histoblasts of the 

 imaginal mouthparts of Musca. The 

 course of the development, in any such 

 detail as really to throw light upon the 

 homologies or phylogeny of the Dip- 

 terous mouthparts, has yet to be traced. 

 The other phase, the comparative 

 anatomical phase, of the study of the 

 mouthparts of the Diptera has been far 

 more successfully attacked. Exhaustive 

 accounts of the morphology of the 



mouthparts of one or of a few species 

 as presented by Kraepelin, Dimmock and 

 others, and comparative studies of the 

 mouthparts of many genera and fam- 

 ilies, as presented by Becher, Smith, 

 Menzbier, Meinert, and others, com- 

 bine to make up a large literature on 

 the subject. Most of these papers 

 make the mistake (as it seems to me) 

 of devoting attention largely to a con- 

 sideration of the more specialized con- 

 dition of the mouthparts as presented 

 by the brachycerous families, and of 

 attempting to interpret homologies by 

 comparing these conditions with the 

 specialized mouthparts of other highly 

 organized insects, as the Hymenoptera. 

 There seems to be no systematic and 

 thorough search for the most general- 

 ized condition of dipterous mouthparts, 

 no attempt to discover the lines of 

 specialization ; the studies seem to be 

 little guided by, and take little advan- 

 tage of, the methods of phyletic study. 

 We know much more about the mouth- 

 parts of the Muscidae than of any one 

 of half a dozen of the nematocerous 

 families. And yet entomologists and 

 dipterologists call the Nematocera the 

 generalized Diptera. 



The notes I have first to present are 

 simply a contribution to our knowledge 

 of the comparative anatomy of the 

 mouthparts of the nematocerous families 

 of the Diptera. Excepting the Ornephi- 

 lidae (represented in America by a single, 

 rare and to me so far unobtainable spe- 

 cies) I have studied the mouthparts of all 

 of these families. The general condition 



