Thorax in winged Insects. 163 
The above eight pieces form the pectus of the mesothorax or medi- 
pectus of Kirby. _ It is difficult to ascertain, from his not separating them 
in his plates, whether the six last mentioned pieces, viz. the episterna, 
epimera and paraptera, have been clearly distinguished by Kirby ; but if 
they have been so, then perhaps the episterna of the mesothorax will be 
the peristethia of Kirby and the epimera his scapularia. The pleure of 
the mesothorax, so called by Audouin, are the union of the episternum, 
parapteron and epimeron. 
Or THE METATHORAX. 
The metathorax of an insect has also, when at its maximum of deve- 
lopement, four pieces to the tergum and eight to the pectus. 
The four superior or tergal pieces of the metathorax are, as in the 
mesothorax, the prescutum, scutum, scutellum, and postscutellum. 
1. The prescutum of the metathorax, like that of the mesothorax, is 
sometimes internal.* In Hymenoptera, however, it is a most conspi- 
cuous piece with many insects. / 
2. The scutwm is sometimes divided into two parts, as in Dytiscus, 
and sometimes connected, as in Lucanus.t+ 
3. The scutellum is the next piece of the metathorax and is composed 
of the postscutellum and postfrenum of Kirby ; this naturalist having 
mistaken the side processes of the scutellum for separate pieces { on ac- 
count of the channel which divides them longitudinally. 
tera generally below. It is a piece which “ se prolonge quelquefois inférieure- 
“ ment le long du bord antérieur de l’episternum, ou bien, devenant libre, passe 
“ au devant de Vaile et se place méme accidentellement au-dessus.’”? On this 
account M, Audouin changed its name from hypopteron to parapteron. In 
Hymenoptera it may often be said to belong to the tergum, and in Coleoptera to 
the pectus. 
* See Ann. des Sciences Nat., Tom. 1, tab, 8. Mr, Kirby calls this piece the 
mesophragma when it occurs in Coleoptera; but in Hymenoptera, he calls it the 
postdorsolum, as will be seen by comparing his figures. 
+ See Int, to Ent. tab. 8. This piece in Coleoptera is Kirby’s postdorsolum ; 
in Hymenoptera he does not appear to have detected it. 
t The metapnystega of Kirby may possibly be the same as Audouin’s peri- 
trema of the Metathorax. 
L2 
