386 ME. A. D. MICHAEL ON HTPOPI, 



Having got my creatures to live, the next step was to watcli 

 the life-history, and observe what this particular Hypojms turned 

 into. I expected to see it turn into Tyroglyphus, and I started 

 several cells with living Hypopi, the cells being divided into three 

 series, differently treated. In series 1 I put only Hypopi which 

 were on the bee itself ; in series 2 only Gramasids bearing 

 Hypopi ; in series 3 both separate Hypopi (as in series 1) and 

 Gamasids (as in series 2). I placed my captures under what 

 seemed to me the most favourable circumstances ; but, to my 

 annoyance, they obstinately refused to turn into any thing ; they 

 lived a considerable time, were tolerably active, but eventually 

 died, and no information was obtained : this was specially true of 

 series 1. As to series 2 I found that the Hypopi which I had put 

 in loose soon got on to the Gramasids, occasionally as many as 

 six upon one Gramasid ; but in the same series, and in number 3, 

 I also found the converse, viz. that the Hypopi gradually left 

 the Gamasids and wandered about loose. I now became afraid that 

 if the Hypopi turned into TyroglypTii, or any thing similar, the 

 Gamasids would eat the adults and I should not see them ; there- 

 fore I gradually removed from some of the cells the Gamasids 

 which no longer bore any Hypopi. Another source of difficulty 

 existed with those cells which contained Gamasids : in order to 

 keep these Acarids in health I have found it best to feed them on 

 cheese-mites {TyroglypJius siro), as I do not know any equally 

 suitable living food which can be procured so easily. I thought 

 I should be sure to know T. siro from any thing that the Hypopi 

 might turn into ; but it was possible they might be so alike that I 

 might not distinguish them. Eegularly feeding the Gamasids with 

 cheese-mites is rather laborious ; so in one cell I tried the effect 

 of putting in a minute scrap of cheese for the cheese-mites to 

 breed in. Coming to examine this cell on 22nd April, ]883, I 

 found, to my surprise, that all the Hypopi had left the Gamasids 

 and were grouped together on the cheese. I removed the 

 Gamasids, and then gently lifted some of the Hypopi off the 

 cheese. I found below them a number of almost globular, milky- 

 white eggs, which struck me immediately as being different from 

 cheese-mites' eggs. Of course the supposition immediately pre- 

 sented itself that the suj)posed Hypopi were not Hypopi at all, 

 but were adult creatures, and had laid these eggs. This, however, 

 required a good deal of confirmation. I removed the eggs and 

 placed them in a separate cell, without any other Acari. I 



