658 EXTERNAL ANATOMY OF INSECTS. 



In most of the apterous hexapods they appear to be 

 attached laterally between the thorax and the pectus*; 

 but in the flea (Pulex) they are ventral. In this tribe the 

 arms are usually stated to be inserted in the head b : but 

 I once succeeded in separating the head of a flea from the 

 trunk, and these organs remained attached to the latter . 

 As to the Octopods and Arachnidce, in the mites (AcarusL..) 

 they are lateral, and in their analogues, the spiders 

 (Aranea L.), they emerge between the thorax and the 

 breast, which last they nearly surround ; in the Phalan- 

 gidce the bases of the coxas approach near to each other, 

 being separated only by a narrow sternum ; in their an- 

 tagonists, Chelifer and Scorpio, they apply to each other, 

 the anterior ones acting as maxillce. In the myriapods 

 the legs of the Chilopoda Latr., and some Chilognatha, 

 as Glomeris, are inserted laterally, a single pair in a seg- 

 ment ; but in Iidus L. their attachment is ventral, the 

 coxae seem to spring from a common base, and there are 

 two pair to each segment d , except the three first, which 

 bear each a single pair. 



I shall next consider how the legs are located with re- 

 spect to each other. To render this clear to you I shall 

 represent each of the variations, which amount in all to 



■ l Mr. Montague describes the legs of NycteriUa, as dorsal (Linn. 

 Trans, xi. 13); but Dr. Leach calls them lateral (Samouelle, 303). 



b iV. Diet, a" Hist. Nat. xxviii. 247. c Plate XXIII. Fig. 4. 



d Plate XXVII. Fig. 58. M. Savigny affirms that these insects 

 cannot have, and really have not, but one pair to each segment ; only 

 that the segments are alternately membranous and shelly, and that 

 the former are concealed under the latter ( Anim. sans Vertebr. I. i. 44.): 

 but, pace tanti viri, I cannot discover that any suture separates these 

 portions from each other : so that, admitting his theory, they must 

 be regarded as two segments soldered together. 



