THORAX OF WINGED INSECTS. 463 



The orders Neuroptera, Trichoptera, Lepidoptera, Hymen- 

 optera, and Diptera, have all the wings essentially formed 

 for flying, hence the anterior or prothoracic segment is of the 

 least extent, and the tergum of the thorax at its greatest 

 development. In those groups, however, which have the 

 lower wings of an inferior size, the metathorax which supports 

 them is generally also reduced. 



In the Lepidoptera the mesothorax is very large, in order to 

 support the ample anterior wings, the scutellum terminating 

 this part behind, as represented in the figures which I have 

 given of the anatomical details of the Lepidoptera, in Griffith's 

 An. K. pi. 121. The metathorax is distinct, but short and 

 transverse. 



Mr. Newman states, {Ent. Mag. I. 409,) that in the Lepi- 

 doptera, owing to the considerable expansion of the lower 

 wings, the metathorax is very apparent ; but in the next page 

 he considers that the first abdominal segment (propodeon) in 

 Cossus is the part which Kirby calls the metathorax, " which 

 I think it cannot be, as the metalw" (by which term he de- 

 signates the hind wings) " are decidedly not attached to it." 

 If the latter supposition were correct, the entire metathorax, 

 which is sufficiently small, would be reduced to a small size 

 indeed, instead of being very apparent ; but this is not the 

 case '. the part which Messrs. Kirby and Spence figure as the 

 metathorax (to which, and not to the description of it, Mr, 

 Newman alludes,) being really such, and having the lower 

 wings decidedly attached to it. 



In the Hymenoptera no difference exists amongst entomolo- 

 gists as to the scutellum of the mesothorax ; — it is that part 

 which immediately follows the large central plate of the 

 thorax (the scutum of the mesothorax), and which in the 

 common wasp is marked by two yellow spots. In some 

 exotic Chalcididso this part is produced into a long thick spine, 

 entirely concealing the abdomen and wings, whilst in others it 

 is extended into a pair of long horns directed backwards. 

 Entomologists, however, are less agreed as to the analogies of 

 the hinder parts of the hymenopterous thorax. Mr. MacLeay 

 considers them to consist of — 



1st, A short transverse piece, which he names the praescutum 

 of the metathorax, and which immediately follows the true 

 scutellum. This M. Audouin considers as the scutum of the 



