166 Mr. W. S. MacLeay on the Anatomy of the 



to prove it. Mr. Kirby is undoubtedly wrong in imagitiing it to belong 

 to the raesothorax, but perhaps not so much in urging that this piece is 

 without a representative in Coleoptera. It would however be contrary to 

 every rule of generalization to suppose that the Hymenopiera could have 

 any piece peculiar to themselves.* Nature, as I before said, works in 

 inferior groups with a given quantity of materials. I have already 

 shewn the tergum of the prothorax to be, at its maximum of develope- 

 ment, composed of four pieces. If these four pieces should^ be nearly 

 equally developed we have a Locusta. If the prsescutum and scutum 

 should be greatly developed the other two pieces will disappear, and we 

 shall have the generahty of Co/eop^era ; while, on the other hand, if the 

 scutellum or postscutellum should be developed considerably, then the 

 other pieces will disappear, and we shall have an Hymenopterous insect.f 

 Now certainly more than one piece exists in the tergum of the prothorax 

 of Hymenoptera. For the prsescutum and scutum of the prothorax, i.e. 

 the pieces which represent what is vulgarly called the thorax of the Cole- 

 optera, do not entirely disappear in Hxjmenoptera as Mr. Kirby says,J 

 since on passing the point of a scalpel under the fore legs of a common 

 Wasp, and so breaking off the prothorax with the head, we shall per- 

 ceive the ring of the prothorax complete, although it is only represented 

 by the ligamentous membrane which connects the two epimera.§ This 



* See Int. to Ent. Vol. III. p. 549. This notion is borrowed from Chabrier, 

 who, however, does not go so far as Mr. Kirby, and fancy that it belongs to 

 the mesothorax. His words are, " la pi^ce superieure du prothorax ou le 

 " collier." 



-j- As a corollary from this, it follows that the Coleoptera which come near- 

 est to the Hymenoptera, are those, the preescutum of whose prothorax is most 

 evanescent, and whose scutellum of the same is most developed. 



X See Int. to Ent. Vol. III. p. 535. 



§ There is one insect, however, which makes me rather doubt whether the 

 structure of the Hymenopterous thorax may not be still nearer to that of Co- 

 leoptera than is stated above. I allude to the Agaon paradoxum of Dalman. If 

 this author's figures be correct, then that most singular Hjmenopterous Insect 

 has the thorax of a Coleopterous one, the prothorax being exceedingly deve- 

 loped, and the rest of the thorax proportionably small. There is, perhaps, 

 little doubt of Latreille being right in making the Chalcid<B come the nearest 

 to the Strepsiptera, Xenos being almost an Hymenopterous genus. 



