366 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



C. Discussion of Results. 



An attempt will now be made to harmonize the results of the various 

 investigators of the muscular changes of Coleoptera. The researches of 

 those who have studied the remaining groups of holometabolic insects, 

 though treated of first, will not be considered in detail, because tlie 

 relation of the changes in Coleoptera to those in the other groups are 

 not yet perfectly clear. It is sufficient to state that the results of this 

 paper are not fundamentally at variance with those obtained by many 

 of these investigators. 



Concerning the state of affairs in Diptera, the following facts are 

 evident from the papers on the subject. In the orthorraphic Diptera 

 there is a persistence of many of the larval muscles. The degeneration 

 of those muscles which disappear during pupal life does not seem to be 

 diflferent from that found in Coleoptera. In the cyclorraphic forms no in- 

 vestigator has found a persistence of larval muscles. Degeneration seems 

 to be the common fate of the larval muscles, a degeneration which 

 takes place by a method different from that found either in Orthorrapha 

 or in other insects. Muscles newly formed in the pupa ai'e very common 

 in Diptera, especially in the higher forms. A true metamorphosis of 

 larval muscles into imaginal muscles has been noted by Van Kees ('88) 

 only. I can confirm from my own observations the metamorphosis of 

 the three pairs of muscles which Van Eees has noted. Contrary to his 

 statement, however, these do not form all of the indirect wing muscles, 

 but only musculus mesonoti, each of the three larval muscles dividing 

 into two fibres, and thus giving rise to the six fibres composing the 

 imaginal mesonotal muscles of each side of the body. A similar 

 development of musculus mesonoti from three pairs of larval muscle 

 fundaments is found in Culex sp. and Chironomus sp. The metamor- 

 phosis of the undoubtedly homologous three pairs of larval muscles in 

 both meso- and metathorax of Thymalus has already been noted 

 (pages 337 and 323, respectively). 



The results of the investigators who . have studied Lepidopterous 

 material are so greatly at variance with one another that little can be 

 stated definitely. The probabilities seem to favor the authors who state 

 that there is a metamorphosis of many of the larval muscles. Perez 

 (:00) states, and probably correctly, that many of the larval abdominal 

 muscles pass into the adult with no changes except a proliferation of 

 their nuclei. 



It is my belief that not one of the investigators of Hymenopterous 



