I once found a Water Mite in the body of a Dytiscus[37]. I was breaking up the beetle, and had removed the elytra and the wings. I only wanted the external skeleton; so a slit was made between the plates of the dorsal and ventral surface, and the intestines removed. The Mite was embedded in the fat-body. I could find no mention in the literature of Beetles or Mites of any similar occurrence; and should scarcely have mentioned it here, had I not been unexpectedly confirmed by my friend Mr. G. E. Mainland, F.R.M.S., who once had a similar experience, and who kindly allows me to quote from a letter he sent me on the subject:-- ‘I am sorry to say I can find no documentary evidence as to the Arachnid I found embedded in the tissues of Dytiscus, but a good deal has come back to my recollection. On removing the right elytron and slitting up the dorsal surface, I found it in the tissue close up to the thorax. I cannot recollect what ultimately became of it, after I had shown it to friends at the Hackney Microscopical Society.... I know that I carefully measured the Hydrachna (which was abnormally large) and its relative size to that of its host, and made a comparison in a lecture (to the Senior Band of Hope at St. Michael’s, Hackney) of a man with a creature as large as a guinea-pig under his shoulder-blade.’ The occurrence of the Mite _inside_ the Beetle was, of course, quite exceptional. It probably found its way in through one of the abdominal spiracles. The Beetle Mite (_Gam´asus coleoptrato´rum_) (Fig. 62) is extremely common, and is parasitic on the Dung Beetle and on the Humble Bee, so that in order to examine the parasite we must capture the host. There can be no difficulty about this, for Dung Beetles and Humble Bees are plentiful enough. This Beetle Mite, apparently, does not infest other species of beetles. I have kept the Devil’s Coach Horse in a bottle with the common Dung Beetle for some months, and though the latter swarmed with these parasites, they never left their host for the other beetle. Even when removed by means of a small brush from one beetle to the other, they left the Devil’s Coach Horse of their own accord, and soon made their way back to the Dung Beetle. [Illustration: FIG. 62.--Beetle Mite.] These parasites, with their host, came into my possession in a strange way. A friend, who knew my hobbies, told me that he had managed to procure for me some young beetles just born. I ventured to suggest that beetles were not born as beetles, but in quite a different shape. My suggestion was received unsympathetically, and I was told that I should alter my opinion when the creatures were sent me. But I did not. The box contained a Dung Beetle, over which were swarming scores of these little Mites, and I had some difficulty in convincing the gentleman who sent them to me that these Mites were not the young of the beetle.