MUSCULATURE OF CULEX PUNGENS. 285 



disappear into the blood stream and become imaginal leucocytes. 

 He says " the degeneration of the larval muscles is entirely chem- 

 ical, there being no evidence of phagocytosis." 



MUSCULAR DEGENERATION IN CULEX. 



In the study of the phenomena attending the postembryonic 

 development, or metamorphosis, of Cnlex, one should first con- 

 sider certain facts in the life history of the insect. Metamor- 

 phosis is complete the insect belonging to the holometabola. 

 Its larval life has as average duration of nine to ten days, and it 

 passes the pupal stage in three days. This, however, is not con- 

 stant and one cannot judge the stage of development of a larva 

 or pupa by the number of days elapsed since emergence from the 

 egg. In isolating a group of eggs in a dish of water one finds 

 pupas at the surface as early as the seventh or eighth day, per- 

 haps, while not all will have reached that stage of their existence 

 until several days later. One then can only judge from the size 

 of the larva as to its stage of development. 



The outward manifestations of metamorphism throw little light 

 upon the internal phenomena attending such change. Several 

 moults may mark the steps of development through the larval 

 and pupal life of an insect and the periods of time between such 

 ecdyses show no change in the external morphology though the 

 internal changes are constantly going on. This fact is well 

 accentuated in Qilc.v, for while the pupa is looked upon as being 

 the stage of transition from the larva to the imago, the histolysis 

 of the tissues does not correspond to this period. Notwith- 

 standing the fact that metamorphism is complete and rapid, 

 Cnlex, unlike the holometabolic insects so far studied, does not 

 go into a resting stage at the end of larval growth. The pupa is 

 very active. What then shall be expected ? Certainly the larval 

 muscles cannot all degenerate and be destroyed during the pupal 

 stage if the insect still is moving its body through the function of 

 these organs. Is there first a new growth of muscles for the 

 imago before the degeneration of the larval fibers ? If such were 

 the case we should look for the phenomena of degeneration in 

 the imago and not in the pupa. 



1 " The Changes which Occur in the Muscles of the Beetle During Metamorphosis," 

 Bull, of Mus. of Comp. Zoo!. Harvard, Vol. XL., No. 7, p. 373. 



