■^ 326. THE INSECTA. 405 



natatorii, saltatorii, rapforii, iWtilfossorriJ^'' The tarsal articles are often 

 ^nlai-ged, 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 

 jirovided with suckers. The last article of these organs bears tisually 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, but 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, tlie hooks are biüdwith Me/oe, and den- Spence (Trans, of the Entomol. Soc. IV. p. 18). 

 ticulate witli the Pompilidae, Hippuboscidae, Cis- 5 Witli the Lepidoi)tera, and Tenthrediuidae. 

 telidae, and with Taphria, Dolichiis, Calathus, 6 W^ith many Diptera. 



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



3 Tliis third liook is found, for e.xample, with with some Blattidae, Acrididae, Pliasmidae, and 

 Lucanus cervus. With larvae of the Meloidae, Psocidae ; among the Hemiptera, with ^can^A/a.?, 

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

 straight, lanceolate hooks, known by the name of Melophagus, Phthiridium, and Pulex jiagel- 

 Triungulinus. Many of the Curculionidae can los. 



grapple olijects by means of the immovable hooks on S With Lampyris, some Blattidae, Coccidae, 

 their tibiae. Bombycidae, Geometridae, also with the Mutillidae 



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



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



two to three. For these lobules, as well as for the W 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- 



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



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



tvall (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 on 



* [ § 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 Locusta expansion of the wings, and upon the relaxation or 

 are closed in a plicated manser 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. 

 ajso flexible. By this arrangement, upon the con- 



