MOTIONS OF INSECTS. DAG 
ranged in bundles, which all look towards the anus; and 
the posterior part is as it were paved with similar hooks, 
but smaller, which point to the head. Thus we may 
conceive, when the animal wants to move forward, that 
it pushes itself by the first set of hooks, keeping the rest, 
which would otherwise impede motion in that direction, 
pressed close to its skin—or it may depress that part 
of the segment; and when it would move backwards 
that it employs the second*. The other descriptions of 
bots, not being embedded in the flesh but fixed to a 
plane, are armed with the mandibles in question, by 
which they can not only suspend themselves in their 
several stations, but likewise, with the aid of the spines 
with which their segments also are furnished, move at 
their pleasure’, Other larvee of flies, as well as the 
bots, are furnished with spines or hooks—by which 
they take stronger hold—to assist them in their motions. 
Those mentioned in my last letter as mbhabiting the 
nests of humble-bees*, besides the six radii that arm 
their anus, and which perhaps may assist them in loco- 
motion, have the margin of their body fringed with a 
double row of short spines’, which are, doubtless, use- 
ful in the same way. 
The next order of alors amongst apodous larvee 
are those that move by means of fleshy tuberculiform or 
pediform prominences,—which last resemble the spurious 
4 Reaum. iv. 416. é. xxxvi.f.5. Compare Clark On the Bots, &c. 48. 
> Mr. Clark (ibid, 62) observed only rough points on the bots of 
the sheep, but these also have spines or hooks looking towards the 
anus. Reaum. iv. 636. ¢. xxxv. f. 11, 13,15. Lalso ohserved them 
] E = € Qoe at ra, rey OND IR 
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