32 Beck, on the Reproduction of an Acarus. 
seeks out the fluids with an apparatus at the mouth, and does 
not leave it until it is entirely empty and shrunken. The 
poisoning process, however, does not occur when this acarus 
feeds, as it frequently does, upon one of its own species. In 
this case the prey continues to move and show signs of life 
as long as any fluids appear to be left in its body, and even, 
when a very small one has been devoured, I have noticed a 
movement of the legs full half an hour from the time of its 
first seizure. 
The parts of the mouth project from the bases of the falces 
and two sharp pointed and close fitting lancets, answer the 
double purpose of piercing and conveying the fluids, which 
appear to be sucked up by a muscular movement at the base 
of the piercers. The acarus is sufficiently transparent for 
the process to be watched under the microscope, and the 
fluids may be distinctly traced in their passage from one 
acarus to the other. 
The external structure of this acarus appears to be very 
simple, and there are but few features to notice besides those 
of the head. Two rows of short hairs, about twenty in all, 
run in parallel lines and a short distance apart, leaving a broad 
central band, underneath which a large vessel is easily 
detected, and appears more or less filled with white floculent 
matter. In no part can I detect any spiracles or tracheae. 
Of the legs, the first pair are during life constantly raised 
and lowered in a vertical direction, and from this peculiar 
action, combined with their two unusually long terminal 
hairs, I presume they are employed as feelers. The last 
joint of each tarsus is furnished at its extremity with two 
hooks and two longitudinal and parallel rows of delicate 
tenent hairs ; by the aid of these this acarus walks with some 
little hesitation in an inverted position upon glass. 
The anus I believe to be represented by two slightly pro- 
jecting flaps at the free extremity of the abdomen, imme- 
diately below which is a longer aperture, from which I 
presume the egg is emitted. 
Wherever this acarus in a natural state deposits its eggs, in 
that part it takes up its quarters and remains for a con- 
siderable time ; this is in fact necessary for the protection of 
its eggs, which would otherwise be devoured by acari of the 
same and probably other species. They will frequently 
destroy their own eggs themselves when disturbed, or when 
pressed for food. 
Having these acari now well established in a cupboard, I 
mostly find them partially concealed in some small cavity, 
and when in a mature state standing over a quantity of eggs 
