INSECTS. 251 
are sete, like as in the beak, which form the sucker (haustellum). 
A triangular upper lip covers the basal piece of the beak in Hem7- 
ptera, as it does that of the snout in Diptera. 
To the head succeeds the trunk or thorax. This part consists 
of three pieces, of which each bears a pair of feet. The first ring is 
named Prothorax, the second Mesothorax, the third Metathorax. In 
four-winged Insects the anterior wings are placed on the middle 
piece, the posterior wings on the hinder piece. The wings of Di- 
ptera are placed on the mesothorax. The inferior surface of the 
trunk is called breast (pectus), on which there is sometimes fixed a 
pointed elongated appendage, the breast-bone (sternum). The 
shield (scutellum) is a part found on the upper part of the thorax 
behind (at the mesothorax) stretching between the wings}. 
The feet are attached on the inferior surface of the body: in the 
hexapod Insects every ring of the thorax carries a pair. Between 
the sternum and epimeron is an articular cavity (acetabulum). The 
first joint is termed hip (coxa, condylus) ; sometimes there is a small 
and very moveable piece between the epdmeron and coxa (trochan- 
tertum, trochantin AUDOUIN), but it is usually wanting or has coa- 
lesced with the cova. The second joint is termed Trochanter, it is 
very small and mostly annular. Then comes the thigh (femur), the 
stoutest, and often also the longest joint of the leg. To it succeeds 
the shank (tibia) more slender, and in general flattened laterally. 
Last is the foot (tarsus), consisting of many joints placed in a line 
like the small bones of our fingers. The number of these joints is 
different in different families; occasionally, in certain coleopterous 
1 The upper surface of the thorax (dorsum of AUDOUIN) may be named notum, the 
under surface sternum, and just as the entire thorax is divided into three rings, so also 
a pronotum and prosternum, mesonotum and mesosternum, metanotum and metasternum 
may be distinguished. Moreover, each ring of the thorax consists of definite special parts, 
which, however, are not distinctly seen in every ring, whilst some coalesce with others, 
or by the greater development of others are suppressed; these parts are a sternwm on 
the under surface, on either side an episternwm as a chief part, and behind this an 
epimeron ; and, finally, on the upper four pieces placed behind each other, to which 
AUDOUIN gives the names of prescutum, scutum, scutellum and post-scutellum; thus 
there are properly three sewlella, but what is usually named scutellwm is a part of the 
mesonotum ; at the sides of the scutwm the wings are attached. Comp. on this interesting 
subject AupouIn, Recherches anatomiques sur le thorax des Animaux articulés, Ann. des 
Sc. nat. 1. 1824, pp. 97—135, 416—432, W. S. Mac-Leay, Comp. Anat. of thorax in 
winged Insects. Zoolog. Journal, No. 18, or Ann. des Sc. nat. XXV. 1832, pp. 93—151, 
with remarks by AUDOUIN and Newport, Topp’s Cyclopedia, 11. pp. 911—924. 
