290 
MR. A. T). MICHAEL ON THE LIFE-HISTORIES 
to use the expression “ cases ” to signify this phase iu the life- 
history ; it must, however, be understood that each case is only a 
nymphal skin, but it is a riymphal skin under special conditions. 
The finely granular marking or wrinkling of the cuticle of the 
species was very apparent, and when a portion was examined with 
a sufficient power this was resolved into the labyrinthine and vermi- 
form wrinkling of which an illustration is given (PI. XVI. fig. 3). 
It was also noticeable that the contents of each case were more 
drawn toward the anterior end than is usual in the nymph during 
ecdysis. Of course the first step was to ascertain that these 
cases were not simply dead creatures ; for this purpose, in the 
latter part of May 1885 I isolated three in a separate glass cell, 
placing them under what experience had taught me would pro- 
bably be favourable conditions of existence. On the 10th June, 
1885, three immature Glyciphagus domesticus emerged from these 
cases. The cases did not split irregularly like an ordinary 
nymphal skin, but opened by the posterior end of the case, 
which had been concave, being pushed out so as to become rather 
convex, and separating from the lateral and ventral portions of 
the case, while it remained attached to the dorsal ; thus when the 
creature within had escaped, the posterior end formed a sort of 
lid attached to the dorsal surface (fig. 4). This I subsequently 
found was the usual, although not the absolutely invariable, mode 
of opening. I did not then examine the precise stage that the 
creatures were in, but I noticed that the cases, although open, did 
not appear to be entirely empty (I subsequently found that what 
they contained was a cast skin). 
On the 10th June, 1885, I placed thirteen more cases in a 
second cell, and submitted them, as I had hoped, to conditions 
similar to the first ; but either from some defect in the arrange- 
ment of the cell, or from unfavourable weather, these specimens 
gradually died, so that toward the end of July there were not any 
alive. On the 30th July, 1885, I again isolated several cases in a 
separate cell. In a week I found that two of them were open at 
the posterior end and that there were two nymphs of Glyciphcigus 
domesticus in the cell ; more subsequently emerged from the 
other cases. I again observed that the cases from which they 
had come did not appear to be absolutely empty. 1 now took 
three of the nymphs which had emerged from the cases and 
placed them in a separate cell ; in about a week they had all 
become inert ; a few days later an adult female of G. domesticus 
