124 INSECTA. 



DoNAciA, Fab. — Leptura, Lin., 



Where the posterior thighs are large and inflated ; the antennae are 

 of equal thickness throughout, and their joints are elongated ; the 

 eyes are entire, and the last joint of the tarsi is enclosed for most of 

 its length between the lobes of the preceding one. 



These Insects ai"e frequently ornamented with brilliant colours, 

 bronzed or gilded. Several are likewise covered Avith an extremely 

 fine and silky down, which may prove useful to them when they hap- 

 pen to fall into water, as they live on aquatic plants, such as the Iris, 

 Sagittaria, Nymphoea, &c., to which they cling with great tenacity. 

 Their larvse live in the roots of the same plants. Their chrysalides, 

 according to the observations of M. A. Brongniart, are attached to 

 their filaments by one edge only, forming knots or bulbs. 



The anatomical researches of M. Leon Dufour have induced him 

 to think that the Donacise should form a particular family. Their 

 hepatic vessels, in number, arrangement, form, and structure, consti- 

 tute a very remarkable exception to those of the Tetramera, and one 

 which even appears to be jjeculiar to these Insects. These vessels 

 only open into the chylific ventricle, while in all the other Tetramera 

 dissected by this able anatomist, they have two insertions, one ven- 

 tricular, and the other caecal. These biliary ducts, only four in 

 number, are of two different kinds ; those of the first are capillary, 

 disposed in two strongly flexed curves, and are inserted by four dis- 

 tinct ends into a short obround vesicle, situated at the inferior and 

 somewhat lateral extremity of the chylific ventricle ; the others, much 

 shorter, thicker, more dilatable, thin and tapering at both ends, have 

 one extremity free, and are separately inserted by the other into the 

 superior and dorsal region of that organ. The whitish pulp con- 

 tained in them is considered by M. Dufour as alimentary matter. 

 The oesophagus is capillary, and without any dilatation in the form 

 of a crop. The chylific ventricle is roughened with very salient 

 papillae. The testes are very similar to those of the LeiDturse. The 

 larvae are naked and concealed, as well as those of the last Longi- 

 cornes, an observation Avhich strengthens the conjectures of M. 



Dufour. 



H.'EMONiA, Meg., Dej, 



The HaemoniK are Donacise in which the penultimate joint of the 

 tarsi is very small, in the form of a knot, almost entire ; the last is 

 very long *. The 



Petaurtstes, Lat. 



United by Fabricius with the Lemse, or our Crioceres properly so 

 called, also have very stout posterior thighs ; but the eyes are emar- 

 ginated ; the antennse, as in the latter, are generally composed of 

 shorter joints, and the lobes of the penultimate joint of the tarsi are 

 much less elongated, and merely clasp the root of the following 

 one ]. 



* The D. equiseti, zosterce, Fab. 

 t The Lema varia, postkata, Fab. 



