^ 326. THE INSECTA. 405 



Tiatatorii, saltatorii, raptorii, and fossorii.^'' The tarsal articles are often 

 enlarged, in which case they form, on their under surface, either a naked, 

 fleshy sole, or a thickly-pilose ball of the foot, which is usually cordiform. 

 With the Dytiscidae, several of these tarsal joints are changed into a disc 

 provided with suckers. The last article of these organs bears usually two 

 movable hooks, which are sometimes deeply bifid or denticulate on their con- 

 cave border.'-' It is rare that there is a third hook between them.'^' But with 

 the Strepsiptera, and Physopoda, all the hooks are wanting. The Diptera 

 and many Hymenoptera, have, moreover, under these hooks, soft lobules 

 (Arolia) provided with numerous small papillae, by means of which these 

 insects can fix themselves to objects.*"" With a great number of larvae, the 

 six legs are very short or abortive, or even completely wanting. In the 

 first case, they consist, usually, of merely a hook, but these larvae have also 

 many short obtuse processes on the other segments of the body, and by 

 means of the hairy soles on the extremity of these, they can fix themselves 

 on bodies and thereby move along.*"'* With many entirely apodal larvae, 

 these processes are replaced by simple tubercles, or by belts of backwardly- 

 pointing bristles or spines, which serve as points of support in their loco- 

 motion. '"> 



The organs of flying are the anterior and the posterior Wings. The first 

 are inserted on the mesothorax, and the second on the metathorax ; but in 

 nearly all the orders, there are genera with which these organs are wholly 

 wanting.''"' In other genera, the females alone are wingless,'*^' which is 

 also true of the neuters of certain families.*'*' It is more common still, to 

 seethe posterior wings changed into balancers ; '^'" and this same transforma- 

 tion occurs also, btit very rarely, with the elytra.'"' The wings, properly 

 speaking, are only prolongations of the cutaneous skeleton traversed by 

 tracheae and blood-canals. Their forms, their nervures, their folds, &c., as 

 well as their sometimes complete abortive condition, may here be passed 

 over, for all these points belong to the domain of Zoology.* 



1 For the marching, leaping, and swimming of steep and smooth surfaces. But this assertion re- 

 insects, see Straus, Consider. &c. p. 180. quires further proof, although it is admitted by 



2 Thus, the hooks are bifid with Meloe, and den- Spence (Trans, of the Entomol. Soc. IV. p. 18). 

 ticulate with the Porapilidae, Hippoboscidae, Cis- 5 With the Lepidoptera, and Tenthredinidae. 

 telidae, and with Taphria, Dolichus, Calaihus, 6 With many Diptera. 



and Pristonychus, of the Carabidae. 7 Among the Orthoptera, the wings are wanting 



3 This third hooli is found, for example, with with some Blattidae, Acrididae, Phasmidae, and 

 Lucanus cervus. With larvae of the Meloidae, Psocidae ; among the Hemiptera, with Jcan<Aja,s, 

 the legs are terminated by three very remarkable, and Rhizobius ; and among the Diptera, with 

 straight, lanceolate hooks, known by the name of Melophagus, Plithiridium, and Pulex flagtl- 

 Triungulinus. Many of the Curculionidae can los. 



grapple objects by means of the immovable hooks on 8 With Lampyris, some Blattidae, Coccidae, 

 their tibiae. Bombycidae, Geometridae, also with the Mutillidae 



4 The Tenthredinidae have a lobule of this kind and the Strepsiptera. 



on each of their legs, and the Diptera have even 9 With the Formicidae and the Termitidae. 



two to three. For these lobules, as well as for the 10 With the Coccidae and the Diptera. The pos- 



tarsi of Insecta in general, see the beautiful figures terior wings are entirely wanting with some Ephem- 



given by Everard Home (Lectur. on Comp. Anat. eridae. 



IV. PI. LXXXI.-LXXXIV.). According to Black- H The two singularly distorted balancers of the 



wall (Trans, of the Linn. Soc. XVI. p. 487, 767 ; Strepsiptera, situated in front of the wings and in 



and Ann. of Nat. Hist. XV. p. 115), the papillae of rapid and unceasing motion, are, from their inser- 



the Arolia secrete a viscid substance which en- tion, only abortive elytra. 



ables the Insecta having these organs to walk ou 



* [ § 326.] Leidy (Proceed. Acad. Sc. Philad. traction of the alary extensors, the spring-like liga- 

 III. 1846, p. 104) has described a peculiar mechan- ments, or ligamenta spiralia, are stretched in the 

 ism by which the membranous wings of Locunta e.xpansion of the wings, and upon the relaxation or 

 are closed in a plicated manner like a fan. This cessation of the action of the muscles, the physical 

 mechanism consists of spiral ligamentous bands, properties alone of the ligamenta spiralia, in re- 

 wound, like the thread of a screw, around the suming their unstretched state, close the wings. — 

 transverse or connecting veins, which latter are Ed. 

 also flexible. By this arrangement, upon the con- 



