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Show 1891.] ASSOCIATION OF GAMASIDS WITH ANTS. 643 them belonging to one of the same two genera, viz. Licelaps or Uropoda, and, as far as I have been able to ascertain, none of them are yet known to science. The most frequent and the most conspicuous of the former genus was a pyriform species which had its dorsal surface dotted at almost regular intervals with wedge-shaped hairs, which give it rather an exceptional appearance ; I propose calling it L. cuneifer. This Acarus was found chiefly deep in the interior of the nest, on the sides and roofs of the passages and chambers, where they were damp without being wet, although sometimes in dry parts, but never in any instance did I find this Lalaps on the Ants themselves. The Ladaps were of both sexes and in all stages ; but even the immature stages of the mite were always on the wood, never on the Ant; yet I never found a specimen except in the Ants' nests. The same remarks will apply to all the Gamasids of the genus Lcelaps which I found in tbe nests of the Camponotus. I thought that this species would be a favourable one to experiment upon, in order to see if I could obtain any idea of the object for which the Gamasid was present in the Ants' nest. In these Gamasince, when the dorsal chitin is thin, as in this species, the principal portions of the alimentary canal, consisting chiefly of the small ventriculus and its four great caeca, can be plainly seen through the dorsal surface as dark objects when they are full of food ; if, however, they are empty they usually become invisible. I collected several suitable specimens of the Gamasid and placed them in the cells which I had formerly used with success in rearing Gamasidce under observation to trace their life-histories-viz. glass rings cemented on to an ordinary 3 x 1 inch microscopic glass-slip, and with the bottom of the cell thus formed lined with blotting-paper, which is kept moist, and a few pieces of suitable sterilized debris placed in the cell; the whole is then covered with a second glass-slip, and two elastic bands or a clip added to hold all together. The Gamasids were healthy when I put them in and their alimentary canals were full of food; I placed some living Ants with them and kept them supplied with living Ants only. The alimentary canals of the Gamasids soon ceased to contain food, and were not replenished, while the creatures themselves became weak and unhealthy. I changed my Gamasids, but with similar results. I then tried eggs, larvae, and pupae of the Ants; but in no case, as far as I could see, did the Gamasids touch them, and their alimentary canals became or remained empty as in the former case. This probably was only what might have been expected, as the Ants would hardly have tolerated in their nests creatures which destroyed themselves or their young ; for such a Gamasid as L. cuneifer would not apparently have any means of defence against so powerful and well-armed an insect as Camponotus herculeanus. I now tried the experiment of killing adult Ants and putting their fresh dead bodies into the cells; very shortly the alimentary canals of all the Gamasids became well-filled, and the creatures strong and healthy. I thought, however, it would be better to avoid any possibility of mistake about this ; so I removed the dead Ants and allowed the canals of the Gamasids |