He apparently drew circles around the head that corresponded to the plates of the dorsal surface, namely (1) the labrum, (2) the clypeus, (3) the front (clypeus posterior), (4) the small sclerites sometimes found around the bases of the antennae, and (5) the epicranium . Otherwise, Banks had to assume that the venom claws had moved forward past the base of the second jaw. This is advocated by Lowne (1892), who regards the three embryonic parts of the preoral region as secondary.
Bengtsson adopts this view of the preoral region, but finds four segments in the postoral part of the head. Patten (1890) gave other reasons for considering each segment as double, derived from a study of the mouthparts and nerves. Verhoeff bases his ideas on a study of the Aptera, the Embiids and the Dermaptera, and especially on a comparison of Javyx with the Chilopoda.
Verlioeff extends his view on the many-segmented structure of the insect lineage to the abdomen (lOtma, li)08c, 1!)04).
THE MirROTHORAX
Here it includes, in the region of the first hour, seven ordinary segments, seven primary segments, and seven secondary segments. Beyond these are the two genital segments, then the segment bearing the cerci, and lastly, in the loavest insects, the traces of the other three beyond the last — pygidium, meta[)Vgi(linm. The gonapophyses and cerci are borne. by the fifteen primitive segments, of sixteen and seventeen, which are the eighth, ninth and tenth permanent segments.
Here there is an apparent lack of harmony, unless the first maxillae of Chilopoda agree with the supralingual of Insecta, the second maxilla3 with the maxillae, and the venomous claws with the labium. In this case, the microthorax of insects could be considered as a maxilliped segment of Chilopods, which from. Comstock and Kochi (1902) considered the gular sclerites of the head to be the microthoracic sternum, and in some Euplexoptera (93) the microthoracic sternites are so large and so connected with the head as to suggest the gular sclerite of Coleoptera.
We can conclude that there is no reason to regard the microthorax as anything other than the neck segment whose sclerites are reduced to the small neck sclerites and the angular plate, when present, whose ganglion is fused with the last main ganglion. , and whose fused appendages are in most cases attached to the head, forming the labium.
THE THORAX
In the Sphingidae the prescutum hangs vertically from the anterior edge of the scutum (155) and. The middle part of the prescutum is completely represented by the very large prephragm Aph). In Calosoma (127) and Dytiseus (128) the prominent shield-shaped region {scl) corresponds to the middle part of the shield of themetanotum.
On the ventral surface of the mesonotum (131) a V-shaped ridge (F) is present similar to that of the metanotum. It is also comparable to the median shield-shaped area of the mesothorax of Coleoptera (127, 128). Very rarely it is wanting, although it is conspicuously the case in the metathorax of most of the Hymenoptera.
The smaller part (tn) is called the 'second antecoxal piece' by Mhat Comstock and Kochi (1902), but this part carries the coxal articulation and is therefore certainly the main art of the trochantin.
THE WING ARTICULATION
GENERAL CONCLUSIONS
Thorax proper consists of three segments, or of three with the tergum of the first abdominal segment added to the Hymenop- . tera. The sclerites are subdivisions of the wall of a primitive segment, and the apparent double nature of each segment is secondary'. The wing support forms an Aving process and the coxal supports the coxal process of the pleura.
In front of the episternum in some of the lower insects there is pre-episternuin. In front of the coxa is the trochantine, a plate possibly derived from the sternum, which articulates above with the episternum and forms below the ventral articulation of the coxa. In the Ephemerida and Odonata the chitinous wing base is directly continuous with the Avails of the thorax.
In all other orders there is an articulation formed by several axillary sclerites in the membranous base of the wing.
SI»Er'IAI. niAKACTEKS OF THE ORDERS
- Propleurum (91) and mesopleurum (94) similar, differing from metapleurum ( 98 )
Pleural wing ]n-ocess (18, ID) divided into two arms, the posterior of which is the true wing process (IIV) that articulates with the wing, while the anterior (//) is an arm that supports the large costal lobe. humeral angle of the wing. A large posterior reduplication (Rd) back of the posterior groove and ridge covers a large ]) art of the mesothorax. The pleural suture (AS') is almost horizontal, but otherwise the meso- and metapleurum are of the typical generalized form.
In the hindwing of the same species (GO), the anal fold and the first anal are normal. In the forewing of the Acridiid?e {Dissosteria G8) the costa (6^) forms the anterior margin, while the subcosta {Se) is clearly double from the base. The upper part of trochantin {Tn) then takes over both the function and appearance of the displaced pleura.
The head of the costa (6') is often separated from the main shaft of the vein (197) and attached to the subcosta {Sc) by a process fitting into a cavity in the head of the latter.
NKUKOPTEKA
564 PROCEEDINGS OF THE NATIONAL MUHEVM. volume xxxvi. . and of two slender lateral strips forming the posterior margin of the notum and terminating in the axillary strings {AxC). The double nature of the meso- and metacoxa3 is common to Neuroptera, Mecoptera, Trichoptera, and Lepidoptera, and it has often ))oen adduced as proof of the double nature of the eutii-e segment. Since, however, in all these orders it can be shown to be a purely secondary adult character, it is clear that it has no such meaning.
TRK^TOPTERA
The protlioracal coxa is not articulated with a true coxal process, but with a completely separate plate in Fas (152 p), which in Protoparcus and Citheronla is fused to the lower end of the episternunium. The meso- and metathoracic coxae in the adult, as in Neurojitera and Trichoptera, are doubly composed of an anterior true coxa {Cse) and a posterior j^late (epm), doubtless derived from the epimere (Epm) as in CorydaUs and Nciironia. The coxae move only slightly on the pleurum and the main movement of the base of the leg is at the articulation between the coxa and the trochanter.
Underside sometimes projecting as a free point articulating with ventral edge of coxa and sometimes obsolete. Mesothoracic notum inconspicuously subdivided into a prescutum {psc) bearing the prephragma (155, Apli), a scutum divided into two lateral lobes {set., set) bearing the anterior notal wing processes (ANP) and, in Phassus , the posterior processes also (150, PNP), and in a scutelhnn (sy-/) foruiiug a posterior triaugle (srJ) whose lateral angles end in the axillary cords (AxC). Probably in most fauiilies the posterior notal wing processes (P.YP) appear to belong to the scutellum (scI) as in Protoparcc (15G).
The jugum (202, Jii), present in lower families, is simply a lobe of the anal region of the forewing and is supported by the last anal vein.
ITYMENOPTKRA
There is nothing in the basal structure of the veins which would invalidate Comstock's interpretation of Ilymenopteran venation, if probable}^ it does not indicate whether M is fused with R or. Two cervical sclerites present on each side of the neck in Ilolorusia (174) and Tcd>anus (179), and several ventral sclerites in the latter and in Ccdlipliora. The trochantine is absent in all three thoracic segments, without the small plate Tnf) of the prothorax is a rudimentar}^ trochantine.
In the meso- and metathorax of Ilolorusia (174) each sternum {S^, . /S'n, S._^) presents a precoxal and a postcoxal plate connecting with. Mesopleurum of Ilolorusia with simple, typical structure butin Tahanus (179) and throughout higher Diptera episternum divided into a large anterior plate (eps) and a less conspicuous posterior part (Eps) that enters the formation of the wing process {WP) . 569, that it cannot be doubted that the sclerite in question belongs to cpisternuni.
174 and 179 probably suggest nothing else than that the mesoe]nsternum {PJpn.,) of the former is similarly divided in the latter into two plates {eps.^ and Kps„). The scutum bears the processes of the anterior notal wing (AN^P) and the scutum the processes of the posterior wing (PN^P) and the axillary chords (AXC). The detailed structure of the base of the latter (211) leaves no doubt that it is merely a modified wing, while a study of a tipulid pupa (173) shows that the halter (W.,) is similar in origin.
Alula a specially developed lobe or lobes of the axillary membrane of the wing (212,Al) encircled by the axillary string (AxC).
GLOSSARY AND SYNONYMY
Cercus Kirby and Spence (182G). Cervical sclerites {mi).— Sclerites of the microthorax situated on the membrane of the neck. Apodema on inner face of]-)leuriiiii along(it Between episterin and epiuieruni, consisting of phural ridge and pleural wing (which see). Eutothorax.— Internal skeleton or apodemes of thorax, including entodorsum ^ enfopleiirum, and entothermmi .
Guide Newport (1830). Tlalfer {Til).— A balance-like representative of the wing in the metathorax of Diptera. Paraptera {P, 1 P, 3 P, 3P, iP).— Small pleural plates at the base of the wing, usually two in front of the pleural wing process and. Radius {R).— The third main vein of the wing, connected at the base with the second axillary.
Suhcosta (Su).— The second main vein of the wing, associated at its base with the first axillary.
BIBLIOGRAPHY
583 appear to be outgrowths of the body wall from the tergo-pleiiral appear to be outgrowths of the body wall from the tergo-pleiiral sutures and are articulated on the wing processes of the tetergum and. Aufsatz: Versuch eines neuen natiirlichen Systems auf vergleichend-niorphologischer Grundlage und denMikrothorax der Insekten.—Zool. Walton, I ^. R. The arrangement of segmental muscles in Geopbilidte and its bearing on the double nature of the segment in Hexapoda and Chilopoda.-Science, XVII, 1003, p. 485.
Voss, F., Über den Brustkorb (Iryllus Domesticus, mit besonderer Berücksichtigung des Flügelgelenks und seiner Bewegung. – Zeit.
EXPLANATION OF THE PLATES
Calosoma scrutator, basal parts of costa, subcosta and radius, showing separate base of costa, separate, ventrally.
