INSECTA. 543 
In Orectochilus (Gyrinus villosus FaBR., StuRM Deutschl. Ins. x. Tab. 
227) the outermost palpiform lobe of the under-jaws is wanting, and thus 
they have only one feeler. So also in many large exotic species. Hence 
this character of the family is not constant, but the agreement of habitus 
does not permit these species to be placed elsewhere. 
B. Abdomen composed of seven segments, the first three connate. 
Dytiscus Li. (exclusive of the Hydrophili, Dytiscus GEOFFR.). 
Antenne longer than head, filiform or setaceous, with eleven joints. 
Eyes marginal. Head retracted within thorax as far as the 
posterior margin of eyes. Posterior cox ample. Maxille arcuate, 
acuminate; external maxillary palps with last joint oval, larger, 
thicker or truncated. 
Compare G. F. Ertcuson Genera Dyticeorwm Berolini, 1832; ejusd. Die 
Kifer der Mark Brandenburg, I. p. 140, &e. 
A. All the tarsi with five joints, anterior of males patellate. 
Dytiscus Cuarrv., nob. (Sub-genera: Cybister Curtis, Acilius 
Leacu, Hydaticus Leacu, Dytiscus Leacu, Ericus.) 
Sp. Dytiscus marginalis L., Rasen Ins. 11. Ins. Aquat. Cl. 1. Tab. 1, LYonET 
Ouvr. posth. Pl. x1. figs. 1—8, Sturm Deutschl. Fauna, Ins. vit. Tab. 185, 
186, DE&JEAN et AuBE, Iconogr. et Hist. nat. des Coleopt. d'Europe, Tom. v. 
Pl. 5, figs. 3, 4; 15” long, feet and body red-brown, thorax and shield- 
covers gleaming black, a yellow-brown border along all the sides of the 
thorax and along the outer edge of shield-covers; the female (Dytiscus 
semistriatus L.) has longitudinal furrows on the shield-covers more than half 
their length. The females also of other species are distinguished by simi- 
larly striated elytra, although in some of these females with smooth shield- 
covers occur. The first three joints of the tarsi of the fore-feet form in the 
male a round disc which is haired on the margin, and supplied with suckers 
below.—Dytiscus (Acilius) sulcatus L., Panzer Deutschl. Ins. Heft 31, 
Tab. 9, 10, Sturm 1. 1. Tab. 189, &c. 
~ 
The larve of these water-beetles have a large oval head, armed with 
strong curved jaws, three pairs of thin haired feet, and two appendages at 
the hind part of the body subservient to respiration. They are very vora- 
cious, and like the larvex of libellz are incessantly on the hunt for other 
water-insects. The nymphs lie concealed in the ground under the water. 
The perfect insects breathe on the surface of the water, by extending the 
abdomen above it, and raising the shield-covers a little, whilst the head 
is kept under. 
The intestinal canal does not undergo any remarkable change in the 
metamorphosis. The four vessels that secrete urine are especially long, 
the rectum has a lateral appendage, membranous and folded. Below the 
rectum are the openings of vessels which secrete a milky fluid. Rampour 
Abhandl. tb. d. Verdauungswerkz. s. 79—82, Tab. um. figs. I—5, Lion 
Durour, Ann. des Se. nat. 111. Pl. 10, fig. 8. 
