DnODOTA, 



INSECTA. 



S.11 



Plpi.)UxilUi<th maxillary-palpi), joined organs, two in number, 

 OM to (eh maxilla, situated on the outer side of the maxilla and 



fc from ttepdp.hr. 

 S order 0i.tf.rVtb* 



i order Diftir* the maxillss are long, slender, and pointed. 

 1 th* Bmimtirm they are still more aUoder, resembling bristles. The 

 lossf slsnrtsr proboseu of the Lfjodoptm consisU of the maxillas. In 

 UM order Hymmifltr* the maxilue are usually Urge, and when closed 

 form a shisHi which covers the various part* of the Ubium. 



The oval apparatus, or Trophi, of the various Haustellate orders of 

 ms*cto hav* each received names from Mr. Kirby. In the order 

 Htmtftm the oval instrument is termed the promuscis. The same 

 part is tanned the Proboscis in the ZMjXero, Antlia in the Lfpidopltra, 

 and Uoetalum in th* Afkarifltra. The several parts representing the 

 mandibles, "m IfN" 1 ", AC., have also received additional names 

 fa) each of these orders, but we have already sufficient 



Th* tarn Thorax is applied to all that part of an insect which lies 

 > th* head and the abdomen, and to which the legs and wings 



11, Larva, bowing the three MgmcuU of the th.Tax and the nine Kg. 

 of tae sbdosaea ; , the thorax ; , the abdomen. 

 % 



We have before said that the thorax is composed of three segments ; 

 Una* are generally distinct in those larva; which do not resemble the 

 perfect insect and which possess legs such as the larva of the 

 LtfiJtf'**, Colmptera, and certain Jfymenoplera (Ttnthredinidce) : 

 hem each of the segments in question possesses a pair of legs. 



:..-. a 



I . . : 



fit. ss. 



; H 



rrt* of Umax oT * Water. Ucelle (Dytunu morftuiu] 

 H. It, OM motr da* of Uw protaorax, wiled pmunwa. ft,. H, the 

 pswt ** of ta Mwtboru, nailed mnoaotun : a, the ncatellum b h-til 



"STJI 1 **;^ ^L 4 ' P " t * HW "" of * = . o of th. middle 

 l-lrofl**.. /V- i, side of the meuthormx, called Ktuternum. 



The term Prothonx is applied to the foremost of the thoracic 

 *Bmntm Mesotborax to the next, and Ketathonx to the hinder 

 m, or that which ioin. the abdomen. In the perfect inasct we find 

 the thre. nmpl. thoracic rings of the larvn rVplaocd by the same 



number of segments, but each divided into several distinct ports; 

 these three segments however are never uniformly developed, but 

 generally two of them are more or less perfected, and exert an inverse 

 influence on the third, and sometimes one of the segments is greatly 

 developed at the expense of the remaining portions. 



The Prothonx bears the anterior pair of legs and is articulated to 

 the head. It is large in the Culeopltra, and is the part called thorax 

 in descriptions of insects of this tribe ; it is likewise well developed 

 in the Orthoptera and Uemijittra. In the Lepidoptera it forms a 

 narrow ring, which is easily distinguished by the scales with which it 

 is covered being erect, those on the next segment being adpressed. 

 In the Hymenoptera the prothorax sometimes forms a distinct neck, 

 but generally it is a narrow plate, and extends back on each side to 

 the base of the anterior wings. 



The upper surface of this segment is termed by Burmeister the 

 Pronotum, and by Audouin and H'Leay the Tergum of the pro- 

 thorax. The latter authors state that the tergum, when perfect, is 

 composed of four parts, to which M. Audouin gives the names 

 Pncscutum, Scutum, Scutellum, and Postscutellum, so named accord- 

 to their succession, commencing at that nearest the head of the insect. 

 These parts however are seldom to be seen, unless it be in certain 

 Orthopterous Insects. 



The underside of the prothorax is called by Burmeister and Kirby 

 the Prosternum, and by Audouin the Pectus of the prothorax. To 

 the proeternum the legs are attached, and hence this part is always 

 tolerably well developed. 



Besides the above parts there is an internal piece called the 

 Antefurca. 



The Mesothorax, or middle segment of the thorax, is more compli- 

 cated than the prothorax, owing to its giving attachment to the ante- 

 rior pair of wings in addition to a pair of legs. The mesothorax is 

 well developed in nearly all insects, and in the order Diptera attains 

 iU largest size, and indeed forms the principal part of the thorax. 

 Its upper surface is termed by Burmeister the Mesonotum (Tergum of 

 Audouin), and the under part the Mcsosternum (Pectus, Audouin). 



Fig. 26 



3,c 



J- 16, upper view of thorax of 1'rtpa Crabro. I, prothorax ; 2, meaothi- 

 ax ; J, metathonx. 1, a, ncutellum j 2, a, acutum ; 2, l>, aquamula 2, c 

 cutellum ; 3, , pnraeutum ; S, 6, acutcllum j J, c, poatacutellum. 



\,t 



Fig. 17, i<ic view of thorax of po Crabro. The Rg\\rct and li-tli-rn refer 

 to the name part* aa in Jig. 28, to which may be added 1, k, pro-scutum and 

 acutum j 1, c, situation of the anterior pair of le(r ; 2, rf, sternum ; 2, r, nitua- 

 Oon of the middle pair of legu; 2,/, situation of the anterior pair of wings 

 3, rf, mctuternum ; 3, e, aitnation of the poaterior pair of winga ; S, / insertion 

 of posterior pair of lega ; 4, abdomen. 



