inhabits, the bat, and that it affords much less shelter than the birds, to any parasite that may be attached to it, especially as the species that I am speaking of is stated usually to fix itself to the membrane of the wings, which being a naked membrane, would seem to expose it to be easily shaken off when the animal is flying: we easily comprehend that it stands in need of some particular provision to counteract this cir

cumstance.

Like those of many other mites, its feet are furnished with a vesicle which is capable of contraction and dilatation, and which the animal can probably use as a sucker to fix itself; but if by any sudden jerk it is unfixed, to prevent its falling, it is gifted with the power of turning upwards, in an instant, two, four, six, or even all its legs, according to circumstances, sufficiently to support itself, and can walk in this position, as it were upon its back, as well as it does in the ordinary way with that part upwards; it may be often seen with four turned upwards while it walks upon the other four,' so that it is ready, upon any accident, instantaneously to use them, and to lay hold of the wing.

The bat is infested by another parasite, placed by Dr. Leach at the end of the Acaridans, and by Latreille, but not without hesitation, after the

1 Baker on Micr. ii. 407. t. xv. f. E. F. G.

2

Diptera. I may therefore be justified in introducing the animal in question here, since, inhabiting the same subject, their proceedings will serve to illustrate each other, and to demonstrate the agency and design of the Supreme Cause in the concurring structure of these parasites. The one I here allude to may be called the batlouse. Latreille, who has described very minutely a species of this genus, informs us that 8. their head is implanted in a singular situation, the back of the thorax, between the middle and the anterior extremity, immediately behind the part to which the anterior legs are attached. The middle of the back, in the common species, presents a cavity, which terminates posteriorly in a kind of pouch, so that the head can be thrown back and its extremity received by it. From this situation, it is evident that the animal cannot take its nutriment from the bat in the ordinary position, with the back upwards; it must, therefore, necessarily stand with it downwards when engaged in suction. When under the forming hand of the Almighty Creator, its legs were planted, it was not on the lower side of the trunk, as they usually are in other hexapods, but on the upper side or margin of that part." Colonel Montague observes,-" So strange and

1 Nycteribia, Lat.

2 N. Blainvillii.

3 See Montague. Linn. Trans. xi. t. iii. ƒ. 5.

N. Verpertilionis.

5 N. D. D'Hist. Nat. xxxiii. 131, 132.

contradictory to experience is the formation of this Insect, that were it not for the structure of the legs, no one could doubt that the upper was actually the under part of the body.' From the account given by the last acute and indefatigable naturalist, the motions of this little creature are so rapid as to be almost like flight, and it can fix itself in an instant wherever it pleases. Putting some into a phial, their agility was inconceivable; not being able, like other Dipterous insects, to walk upon the glass, their efforts were confined to laying hold of each other, and during the struggle they appeared flying in circles." 2

Their head is furnished with antennæ and feelers, immediately below the insertion of the former, on each side, is a slightly prominent eye, so that they have sight to guide them in their motions, which the bat-mite appears to be without.

I may conclude this account with the pious reflection of the worthy author lately mentioned. The very singular structure of this insect, which, at first, appears to be a strange deformity in nature, and excites our astonishment, will, like all other creatures, constructed by the same Omnipotent hand, be found to be most admirably contrived for all the purposes of its

creation; and the scrutinizing naturalist will soon discover this unusual conformation to be the character which at once stamps its habits and economy.'

One of the most singular animals of this Class is one called the vegetating mite.' These are fixed for a time, by an anal thread, to certain beetles, by means of which, as by an umbilical chord, they derive their nutriment from them. After a certain time, they disengage themselves, and seek their food in the common way of their tribe.

It is difficult to say where Latreille's Order of Aporobranchians should properly be placed. Savigny considers them as leading from the Crustaceans to the Arachnidans by Phalangium. If they are parasitic upon marine animals, as there is reason to believe, might they not, in some sort, be regarded as one of those branches, which, without going by the regular road, form a link between tribes apparently distant from each other? They seem, in some respects at least, to present an analogy, if not an affinity, to the Hexapod parasites, the bird-louse,' &c. I offer this merely as a conjecture.

3

1 Linn. Tr. xi. 13.

Nymphon. Pycnogonum, &c.

5 Nirmus.

2 Uropoda vegetans.

See above, p. 18.

310

CHAPTER XX.

Functions and Instincts. Insect Condylopes.

THE animals of the class we are next to consider, have been regarded by many modern zoologists, especially of the French school, as inferior both to Crustaceans and Arachnidans, on account of their having only, as it were, a rudimental heart, exhibiting indeed a kind of systole and diastole, but unaccompanied by any system of vessels by which the blood might circulate in them. A learned and acute writer, and eminent zoologist, amongst our own countrymen, has with great force controverted the justice of this sentence of degradation pronounced upon Insects; an opinion which has also been embraced by many other modern writers on the subject, and considerable doubt has been shown to rest upon the main foundations upon which the illustrious and lamented Baron Cuvier, who was the father of the hypothesis, had built it.'

But the important discoveries of Dr. Carus, who first proved that a circulation really exists in various larves of Insects, and afterwards that

1 Mac Leay, Hor. Entomolog. 204, 297.