THORAX OF WINGED INSECTS. 465 



clearly visible. This is especially the case in Chlorion and 

 Peloj)CBus. 



I shall not here enter into further details in support of 

 my rejection of the views of the French entomologists, and 

 of my opinion that the two last-mentioned pieces are thoracic 

 and not abdominal. Indeed my only reason for noticing 

 these controversial opinions in this place, is in conse- 

 quence of the general similarity of structure which exists 

 between the Hymenopterous and Dipterous thorax ; the ter- 

 minal portion of the thorax of the latter being in like manner 

 considered as portion of the abdomen by the French entomolo- 

 gists, the halteres, consequently, as abdominal appendages, and 

 the winglets of the Diptera as a pair of rudimental lower wings. 



Latreille, considering the hinder part of the thorax as ab- 

 dominal, says of the alulae — " Par leur position ces appendices 

 auraient plus de rapports avec les ailes inferieures que les ba- 

 lanciers;" adding, however, — "lis me semblent neanmoins partir 

 d'un point un peu plus eleve que les ailes," i. e. the inferior ; 

 which, if we regard the terminal portion of the thorax as tho- 

 racic, clearly proves them to be appendages of the upper wings. 



On examining one of the small Tipulidae — Chirononius, for 

 example — the portion of the thorax to which the fore-wings 

 are attached is very large, the hinder part being elevated into a 

 lobe-like scutellum, corresponding exactly with the mesothoracic 

 scutellum of the Hymenoptera. Behind this is another segment 

 of the metathorax, to which the hind legs are attached, having 

 also attached on each side one of the halteres. 



In the Crane Flies {Tipula oleracea) we find the same for- 

 mation, except that the mesothoracic scutellum is not elevated, 

 whilst the metathoracic scutellum (adopting the views of Mr. 

 MacLeay)!' is very conspicuous, nearly square, and almost 

 horizontal. The halteres arise as in the former,*^ having a 

 spiracle near the base of each. 



'' In the wasp the metathoracic scutellum of MacLeay is generally longitudi- 

 nally divided by an impressed line. The same occurs in the part under con- 

 sideration in Tipula crocata. From analogy, however, with the large extent of 

 the mesothoracic scutum, I formerly regarded this, from its dimensions, as the 

 metathoracic scutum. (Griff. Tr. An. K. pi. 122, fig. 1 — 4.) The non- or hut 

 slight development of the other divisions, renders the determination of this 

 question very difficult. 



•■ On following the lateral demarcation of the dorsal pieces of the metathorax, 

 it is evident that the halteres and their spiracles are placed, not upon the con- 

 NO, V. VOL. v. 3 O 



