238 
Formation of a Cocoon 
2. “ Some large larvae of M . stabulans Fall, were placed in a jar containing 
sand. On examination some days later, small oval lumps were seen amongst 
the loose sand. These lumps consisted of grains of sand cemented together to 
form cases round the puparia.” 
Similar cases, containing the puparia of M. stabulans, were also recently 
found by Mr Collin, who kindly sent me a couple of these cases which enabled 
me to confirm the previous observations. The cases received from Mr Collin 
are exceedingly fragile and composed of small grains of sand cemented 
together with an imperceptible secretion; the cases are oval in form with a 
rough external surface and smooth inside. 
As the formation of a cocoon or a case is now proved for two species of the 
genus Muscina, M. stabulans and pabulorum, it is surprising that it has not yet 
been found in another very closely related species, M. assimilis Fall., of which 
I have examined a number of larvae and pupae, without noticing the slightest 
trace of a cocoon or a case. It is possible, however, that under other conditions 
than those which prevailed in my experiments the larvae of this species may 
produce a cocoon which surrounds the puparium. 
