25 
The President's Address. By A. D. Michael. 
beetle grubs up anything they are in a favourable position for taking 
advantage of it ; and endless other varieties. But perhaps one of the 
oddest sorts of parasitism was pointed out by Megnin of Vincennes. 
If you examine the skin of a freshly killed old rabbit, you will probably 
find plenty of a strange and comical -looking truly parasitic Acarid, 
the male of which strikes one at first rather as if it had put [on a 
microscopic Ethiopian serenader’s long-tailed coat ; this gentleman is 
Listrophorus gibus. Many Acari which live on mammals have 
singular apparatus for holding on to their hairs. The Myobia of the 
mouse and bat has a short stumpy front leg, quite different from its 
other legs, terminated by a great curved and flattened claw which 
curls round a hair and presses it against a chitinous peg on the 
tarsus, so that it is held between the two as in a vice. The Hypopi of 
the Dermacarus sciurinus of Haller, a parasite of the squirrel, and 
of the somewhat similar parasite of the mole, have a longitudinal groove 
on their ventral surface in which a hair lies, and movable chitinous 
plates which close above the hair and press it down into the groove. 
But Listrophorus is the oddest of all, for it has the under-lip expanded 
on each side into a flexible chitinous plate which curls round the hair 
and holds on very tightly, so that the rabbit could not detach it. But 
in spite of this the Listropliorus does not remain in peace. You will 
probably also find among the hairs another Acarus, Cheyletus parasiti- 
vorax , which, like all other members of the genus, is a most ferocious 
creature. Megnin wanted to study the Listrophorus and put twelve 
in a glass cell, but he accidentally also put in two of the Cheyletus, 
which is about the same size as the Listrophorus ; to his astonishment 
the two killed and sucked the twelve before his eyes in a very short 
space of time. Thus the Cheyletus lives permanently upon the rabbit, 
not to eat him or do him any harm, but to use his fur as a hunting- 
ground wherein to chase creatures that really do injure the host. 
How let me treat of a few matters affecting particular families 
only. I will not tire you by going through all, nor by attempting 
any systematic treatment, but will confine myself to the development 
of a few points in some of the leading families. One of the lowest of 
these great groups is the Sarcoptidae, which by common consent is 
divided into at least two sections, — the Sarcoptinae or Itch-Mites, and 
the Analgesinae or Bird’s Feather Parasites. The former are minute 
creatures degraded by parasitism, and by no means rich in number of 
species; but if you want to attract public attention, probably the 
best way is to make yourself eminently disagreeable to everybody. 
Beranger once wrote that “ Love was not like fear for paying,” and 
accordingly more attention and literature has probably been devoted 
to the Itch-Mite than to the whole of the rest of the Acari na put 
together. In Fiirstenberg’s magnificent work on these creatures, 
published in 1861, no less than 172 folio pages are devoted to a 
summary of the previous literature, as against 50 pages of original 
matter. 297 books and papers on the subject are enumerated in his 
