PRESIDENTIAL ADDRESS. 7 



found both in ponds and running streams. The latter crawl 

 slowly over the mud and w^eeds, and constitute the link between 

 the Tro77ibidii and the Hydrachnidce. The Halicari?ice are chiefly 

 marine, and may be met with in numbers in the sea-weeds of our 

 coasts from low to high water-mark and even above, where the 

 \vaves sometimes reach. In colour they vary from w^hite and 

 black to red. 



The next family, MyobiidcE, are found upon the fur of rats 

 and mice and other small mammals. Their styliform rostrum 

 doubtless enables them to draw upon the juices of their host, 

 while, with the singular, twisted, clasping apparatus, provided on 

 the first pair of legs, they cling firmly to their hairs. Musculus is 

 said chiefly to affect the head and shoulders of the common 

 mouse ; but, so far as my experience goes, it is equally spread 

 over the whole body. Upon the rat they are usually quite as 

 numerous ; but I have my doubts as to whether these are not 

 another species, the females differing in the character of the 

 abdominal hairs as well as in other ways. 



To this family belongs that interesting genus, Disparipes^ 

 sometimes found in considerable numbers upon the various Bombi 

 and also upon the nymphs of coleoptratonim, with which these 

 are infested. They are provided wdth large, sickle-shaped claws 

 upon the first pair of legs^ by which they hold on grimly to the 

 hairs of the bees or of their parasites. There is little doubt that 

 other species may be found belonging to some of the smaller 

 bees, if carefully sought for when opportunity occurs. Pygmepho- 

 riis will rightly find its place in this family. It may frequently be 

 found in some numbers clinging to the hairs of the thoracic spira- 

 cles of stercorariiis. 



It would carry me much beyond the limits of my address, and 

 I fear of your patience, were I to do more than glance at the 

 remaining families, which constitute the Acari proper or the 

 Atracheate group of the Acari7ice. 



Suffice it to say that in the Tyroglyphidce, we get that peculiar 

 and interesting phase of mite-life, known as the Hypopial stage, 

 wherein certain individuals assume temporarily entirely different 

 characters from the ordinary nymph, and by attaching themselves 

 to other creatures are carried to " fresh fields and pastures new," 



