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 the 
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 
different 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 are very common 
in Diptera, especially in the higher forms. A true metamorphosis of 
larval muscles into imaginal muscles has been noted by Van Rees (’88) 
only. I can confirm from my own observations the metamorphosis of 
the three pairs of muscles which Van Rees 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. Pérez 
(: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 
