237 
SUPPLEMENTARY NOTE ON THE FORMATION OF A 
COCOON BY CYCLORHAPHOUS DIPTEROUS LARVAE. 
By D. KEILIN, Sc.D. 
(From the Quick Laboratory , University of Cambridge.) 
The formation of a cocoon or of a more or less solid case by a larva before its 
transformation into a pupa, occurs very seldom in cyclorhaphous Diptera. 
This is due undoubtedly to the existence in all these Diptera of a puparium 
formed bv the contracted and hardened last larval skin, in which, as in a 
cocoon, is contained the real pupa or chrysalis of the fly. 
In the appendix to my paper on Anthomyid larvae 1 I gave a complete 
account of all that is known of cocoons in cyclorhaphous Diptera. This 
pertained to but five species: Myospila meditabunda F., Mydaea pertusa Meig., 
M. anomala Jaen., M. pici Macq. and Passeromyia heterochaeta Villeneuve. 
In the same paper, when dealing with the life-history of Muscina stabulans 
Fall., I referred to Dufour’s paper (1840) 2 in which he stated that the pupa of 
this fly, bred from Agaricus campestris, were surrounded by a cocoon formed 
by a paste of moistened paper which was left with the fungi in one of his 
breeding-jars. 
As this observation was not confirmed by other entomologists who studied 
M. stabularis, I considered it as somewhat doubtful. I am now able, however, to 
assert that Dufour’s observation was correct and that it was recently confirmed 
independently by Dr G. S. Graham-Smith and Mr James E. Collin. I owe the 
following information relating to Muscina pabulorum Fall, and M. stabulans 
Fall., during the year 1916, to the courtesy of Dr Graham-Smith. 
1. “Females of M. pabulorum Fall, were placed in a glass jar, covered 
with wire cloth, containing the body of a recently killed guinea-pig.... 
The puparia were found in detached masses of hair arranged like the cells in 
a honeycomb, each puparium lying in a tough case mainly composed of hairs.” 
1 Parasitology, ix. 325-450 (1917). 
2 Dufour (1840). “Second memoire sur les metamorphoses de plusieurs larves fongivores 
appartenant a des Dipteres.” Ann. de Sc. Nat. 2 e serie, xm. 148-163, PI. m. On page 157 of this 
paper we read as follows: 
“Au moment de leur transformation en pupe, ces larves m’ont fourni un fait assez singulier. 
Dans le bocal ou je les elevais, jj’avais laisse du papier qui, incessamment humecte par la decom¬ 
position du champignon, se reduisit en pate. Je trouvais plusieurs pupes enveloppees d’une espece 
de cocon ou de fourreau forme avec cette pate; mais toujours lc bout anterieur, celui par lequel 
devait avoir lieu l’eclosion, etait decouvert. D’autres pupes etaient nues au milieu du magma ou 
dans le sable qui garnissait le fond du vase.” 
