472 MOTIONS OF INSECTS. 



meal of the various species of animalcula, abounding in stagnant waters, 

 that come within the vortex thus produced. As thfese animals require to 

 be firmly fixed to the substance on which they take their station, and their 

 back is the only part, when they are doubled as just described, that can 

 apply to it, — they are furnished with minute legs armed with black claws, 

 by which they are enabled to adhere to it. Tliey have ten of these legs: 

 the four anterior ones, which point towards the head and are distant from 

 each other, are placed upon the fourth and fifth dorsal segments of the 

 body ; and the six posterior ones, which point to the anus and are so near 

 to each other as at first to look like one leg, are placed on the eighth, ninth, 

 and tenth. When the animal moves, the body continues bent, and the 

 sixth segment, which is without feet, and forms the summit of the curve, 

 goes first. ^ De Geer named the fly it produces Tipula amphibia : it 

 seems not clear, from his figure, to which of the modern genera of the 

 TipularicB it belongs ; nor is it referred to by Meigen. 



1 come now to the jumping apodes ; and one of this description will 

 immediately occur to your recollection, — that I mean which revels in our 

 richest cheeses, and produces a little black shining fly {Tyrophaga Casei). 

 These maggots have long been celebrated for their saltatorious powers. 

 They effect their tremendous leaps — laugh not at the term, for they are 

 truly so compared with what human force and agility can accomplish — 

 m nearly the same manner as salmon are stated to do when they wish to 

 pass over a cateract, by taking their tail in their mouth, and letting it go 

 suddenly. When it prepares to leap, our larva first erects itself upon its 

 anus, and then bending itself into a circle by bringing its head to its tail, 

 It pushes forth its unguiform mandibles, and fi:ies them in two cavities in 

 Us anal tubercles. All being thus prepared, it next contracts its body into 

 an oblong, so that the two halves are parallel to each other. This done, 

 it lets go its hold with so violent a jerk that the sound produced by its 

 mandibles may he readily heard, and the leap takes place. Swammerdam 

 saw one, whose length did not exceed the fourth part of an inch, jump in 

 this manner out of a box six inches deep ; which is as if a man six feet 

 high should raise himself in the air by jumping 144 feet 1 He had seen 

 others leap a great deal higher.^ The grub of a little gnat lately noticed 

 (Chironomus stercorarius) has a similar faculty, though executed in a 

 manner rather different. These larvae, which inhabit horse-dung, though 

 deprived of feet, cannot move by annular contraction and dilatation ; but 

 are able, by various serpentine contortions, aided by their mandibles, to 

 move in the substance which constitutes their food. Should any accident 

 remove them from it. Providence has enabled them to recover their natural 

 station by the power I am speaking of. When about to leap, they do not, 

 like the cheese-fly, erect themselves so as to form an angle with the plane 

 of position ; but lying horizontally, they bring the anus near the head, 

 regulating the distance by the length of the leap they mean to take ; 

 when fixing it firmly, and then suddenly resuming a rectilinear position, 

 they are carried through the air sometimes to the distance of two or three 

 inches. They appear to have the power of flattening their anal extremity, 



' De Geer, vi. 380. t. xxiv. f. 1—9. Mr. Weslwood refers this insect to the modern genus 

 Dizn. {Mid. Cfa.<is. ii. p. 527.) 

 2 Swamui. BM. Nat. Ed. Hil], ii. 64. b. 



