226 
Observations on the various Insects 
The Class Arachnides embraces the millipedes, spiders, 
lice, mites, ticks, &c. Amongst the last are included the little 
panisites before us, the first of which belongs to the Ordkr 
AcERA, Family RiciNiE or Ticks, Genus Uropoda of La- 
treille. The Baron De Geer describes a tick nearly allied to ours 
under the name of Acarus vegetans ;* but as that species is at- 
tached by the apex of the body and this by the back, I am induced 
to thinkjt a distinct species, which 1 shall call 
14. Uropoda umbilica. It is oval, rusty-brown and shining ; the 
upper side horny, shield-shaped, convex and punctured, with longish 
scattered hairs. From the back, but a little on one side, arises a pe- 
duncle (fig. 49, s), which is white, transparent, as long as the animal, 
sometimes gradually increasing to the extremity, which is attached 
to the elytra of the Elater (fig. 48, ?•). It has eight short-jointed 
legs more or less clothed with hairs, which in repose are pressed 
close to the underside : the first pair seem to be somewhat palpi- 
form and a little the longest, especially in the terminal joint, which 
is densely hairy at the apex ; the second pair are the sliortest, simi- 
lar to the preceding, but tapering and less hairy ; the others are 
terminated by a slender transparent clavate joint, destitute of 
hairs (fig. 48, q ; the natural size). 
This curious tick infests the Elater ohscurus (fig. 48), attaching 
itself in considerable numbers to the wing-cases by a singular 
contrivance in the shape of a thread, which is fixed by one end to 
the lick and by the other to the click-beetle. This is probably a 
provision to prevent the tormented animal from rubbing off his 
parasites : they are able, according to the remarks of De Geer, to 
remove when they please, by crawling in a certain direction until 
the cord is sufficiently strained to cause the end to be detached 
from the beetle. It has been supposed that these animals obtain 
their nutriment through this tube; and whether they possess a 
rostrum for sucking I have not been able to ascertain, from the 
extreme minuteness and obscurity of the head. 
The other parasite belongs to the same OuDER AcERA.f but to 
the Family Microphthira, and the Genus Leptus, Latreille. 
It infests the click-beetle named Elater ruficaudis. which has 
been already described and figured. J It is a very different little 
animal to the Uropoda umbilica, thrusting its beak into the punc- 
tures of the thorax and elytra of the beetle, and thus absorbs the 
juices (fig. 50, t). The dreadful pest called the harvest-busr, § 
which insinuates itself into one's legs, causing an insupportable 
* Ml' moil t's pour servir a I'Histoire des Insecles, v. vii., p. 123, pi. 7, 
fig. 15 and 16. 
T Latreille, in his later works, makes this a family only of liis Arach- 
nides. 
X Vide pi. I., fig. 12. 
^ Leptut autumnulu, figured in Shaw's Zool. Misc., vol. ii. pi. 42. 
