574: EXTERNAL ANATOMY OF INSECTS. 
14. Mesostethium*. This part in Coleoptera is termi- 
nated anteriorly by the peristethium, scapulars, and me- 
sosternum, laterally by the parapleure >, and behind by 
the cove of the posterior legs‘, which generally are in- 
serted transversely between it and the abdomen. It is 
commonly very wide; but in the ground beetles (Eutrech- 
ina) and water-beetles (Zunechina), &c., in which the 
coxe and parapleure are dilated, it is proportionally re- 
duced: its length is regulated by the distance of the in- 
termediate and posterior legs; where these are far 
asunder, as in the rose-scented Capricorn, &c. it is long: 
but where they are near each other, as in the Scarabeida, 
it is short; its width, however, generally exceeds its 
length. In shape it is generally subquadrangular ¢, 
though sometimes rhomboidal, and other forms of it oc- 
cur. Between the hind-legs it generally terminates in a 
notch or bifurcation distinct from the metasternum, as in 
Hydrophilus, &e.; in Hister there is no notch, and in 
many Scarabeide it projects between the hind-legs in a 
truncated or rounded mucro; in the Vesicatory beetles, 
Cantharis, &c. it is more elevated than the medzpectus, 
towards which it descends almost vertically; in Dytiscus 
L., Carabus L., &c. this part is usually divided into two 
by atransverse sinuous channel, and in Elater by a lon- 
gitudinal straight one. In many Orthopterous genera, 
Gryllotalpa, Acrida, Locusta, &c., the mesostethium con~ 
sists of zwo piecese. It is remarkable that in many of 
these genera, in this part, as likewise in the medzpectus 
and antepectus, are one or more perforations which ap- 
* Prates VIII. IX. y’. » Prate VIII. Fic. 4. 2’. 
* Ibid. p”. 4 Ibid. 2/. 
e Ibid. Fic. 13. y'. a +. 
