394 PHYSIOLOGY OB THE INVERTEBRATA. 



in the act of flying, as is the case with the Lcpidoiptcra^ Hi/men- 

 oiptcra, the majority of the Ncurojitera, the ZihcUi(dickc, Pciiidm, 

 and finally, the Cicadidm, and the Ajyhididw. The muscles 

 of the anterior wings are comparatively smaller than those of 

 the posterior, when the first are not used, properly speaking, 

 except to cover the latter, as is the case with the Coleoi^tera, 

 the Bugs, and many of the Ortlwptcrar (Von Siebold.) 



There are also certain accessory organs which aid in the 

 phenomenon of flight. Prof. Huxley says that " the air-sacs 

 doubtless assist flight by the diminution of the specific gravity 

 of the insect, which follows upon their distention." 



Concerning the phenomenon of flight Sir Richard Owen 

 has justly remarked that " in no part of the animal kingdom 

 is the mechanism for flight so perfect, so apt to that end, as 

 in the class of insects. The swallow cannot match the dragon- 

 fly in its aerial course ; this insect has been seen to outstrip 

 and elude its swift pursuer of the feathered class : nay, it can 

 do more in the air than any bird — it can fly backwards and 

 sidelong, to right or left, as well as forwards and alter its 

 course on the instant without turning." * 



The Arachnida. 



In the Arachnida the organs of locomotion are all fixed to 

 the cephalo-thorax, and consist of eight pairs of limbs, strongly 

 resembling those of the Inseda ; and almost always terminated 

 by two hooks. The length of these organs is generally con- 

 siderable, and they easily break ; but, as in the Crustacea, the 

 stump, after having cicatrised, reproduces a new limb, which 

 increases by little and little, and ends by becoming similar to 

 that of which the animal had been deprived. 



* The flight of the bee exceeds twelve miles an hour, and it will "go four 

 miles in search of food. Its wings, braced together in flight by a row of 

 booklets, bear it forward and backward, upward, downward, or suddenly 

 arrested course, by a beautiful mechanical adaptation. (See Cowa.ii's Ifonei/ 

 Bee.) For a full exposition of the flight of insects the reader is referred 

 to the work of Chabrier in Mem. (hi Museum, tomes 6-8 



