300 MR. A. D. MICHAEL ON THE 



as a rule, the Gainasinse are predatory creatures, and that their 

 being found in the situations before described is due to the fact 

 that soft-bodied Acari, and minute soft-bodied insects &c, abound 

 there, and afford ample prey. 



While on this subject of the food, I wished, if possible, to ascer- 

 tain whether the nymphs and females of Gamasinse do really suck 

 the juices of the insects upon which they are found, or only use 

 them as a means of conveyance, as Megnin contends. With this 

 object, I placed a single Gamasid in a separate cell, and after a day 

 or so ceased feeding it with a very sufficient supply of cheese- 

 mites, but instead introduced some freshly killed dipterous insects, 

 selecting those the juices of which would be dark or of strongly 

 marked colour. The Gamasinse, like many other of the Acarina, 

 are sufficiently transparent to allow the colour of the food to show 

 through the dorsal surface, looking like coloured markings ; a cir- 

 cumstance which, not being understood by C. L.Koch*, induced 

 that most laborious writer to create a great number of new spe- 

 cies, dependent upon colour, which arose from the nature of the 

 food the creature had been eating. I invariably found that for 

 a day or so the Gamasus assumed the colour of the insect sup- 

 plied to it. Thus after a black gnat had been put in, the markings 

 on the Gamasus were black, after a scarlet Trombidium they were 

 red ; and I also observed that if the insect were at all large, the 

 Gamasus seemed to prefer attacking the eye, and was then coloured 

 for a day or so in accordance with the pigment-layer. It is there- 

 fore evident that the Gamasids do suck the juices of quite freshly 

 killed insects ; and although it is most difficult to watch them on 

 the living insect, I cannot help thinking that they do obtain some 

 amount of nourishment at the expense of their hosts during the 

 period of their parasitism, or at all events that this is the case with 

 some species. 



Having now disposed of the question of food, I will relate the 

 other observations which I was able to make ; but before doing so, 

 in order that the points I wished to elucidate may be understood, 

 it is, I fear, necessary to show, very shortly, what other writers 

 have done on the subject, and where the divergence of opinion 

 principally exists. 



Linnaeus, who did not divide the Acari into families, found 



* ' Deutschlands Oustaceen, Myriapoden und Arackniden' (Regensburg, 

 1839). 



