174 Mr. W. S. MacLeay on the Anato^iy of the 



" prosternum'' is a " longitudinal or other elevation of the antepectus 

 " between the fore-feet." I conceive therefore that he gives the name 

 of prosternum only to that part of the sternum of the prothorax in a 

 Polistes virhich resembles the escutcheon, and that he would call all the 

 rest part of the antepectus. 



2. The antefurca is considerably developed, the middle process be- 

 ing connected w^ith the sternum and the lateral process wnth the epimeron ; 

 the interval forming part of the acetabula of the fore feet.* 



3. The two episterna are each very large, and occupy great part of 

 the antepectus. These pieces, together with the epimera, form the ante- 

 pectus of Kirby, who has not distinguished between them.t 



4. Ths two epimera are situated above the antepectus, are smaller 

 than the episterna, on which they rest, and are connected together above 

 by a hgamentous membrane, which is the representative of the horny 

 shield of the prothorax in Coleoptera.% 



2. Of the Pectus of the Mesothoiiax. 



1 . The sternum of the mesothorax is large and broad, occupying the 

 wholefront of the medipectus except for a small space at the two upper 

 angles. It is therefore somewhat of a quadrate form.§ The peristethium 

 of Kirby in Hymenoptera is the fore part of the sternum, this author not 

 dissecting the pieces according to their sutures,|| and therefore confining 

 the name of mesosternum to only that part of the sternum of the meso- 

 thorax which is between the legs. 



2 . The medifurca is very beautiful, exactly resembling the Greek 

 letter Y with its arms joined by a cross line.^f 1 



3. The episterna of the mesothorax are two sub-triangular pieces, the 

 three sides of which are bounded by the collare or scutellum of the pro- 

 thorax, the sternum and the epimeron of the mesothorax.** The wings 

 are inserted at one of the angles of these lateral sub-triangular pieces, 



* Fig. 8, Z. t Fig. 8, F. 



X Fig. 8, A. § Fig. 9, Q. 



II It may be proper, however, to observe, that although the pieces are here 

 confluent, each pectus contains typically four pieces to its sternum, 

 f Fig. 9, Y. ** Fig. 9, S. 



