324 



DOMBEYA DORITIS. 



cautiously along, and jumping from considerable dis- 

 tances upon flies and other insects. The Dolomedcs, 

 however, at the period of laying their eggs, form a 

 little web upon the plants, within which a cocoon-like 

 mass may be observed which contains the eggs. 

 These they guard with great caution, as well as the 

 young as soon as they are hatched. Moreover, when 

 disturbed, they run off with their egg bag. The type 

 of the genus is the handsome Aranca marginata, found 

 on the margins of streams, and figured in Kirby and 

 Spence's Introduction to Entomology, vol. ii. pi. 5, 

 fig. 4. 



DOMBEYA (Cavanilles). A genus of ornamen- 

 tal trees, indigenous to the islands of Bourbon and 

 Mauritius. Linntean class and order, Monadelphia 

 Dodecandria, and natural order Byttncriaceae. Gene- 

 ric character : calyx five-parted ; stamens numerous, 

 growing out of the base of the tube. Ligulae long, 

 and linear between every three stamens ; style fili- 

 form, five-cleft at top, stigmas reflexed : capsules five, 

 one or many-seeded, two-valved, united ; seeds ob- 

 long. These plants are grown in loam and moor- 

 earth, and are propagated by cuttings in sand in a 

 moist heat. 



DO NAG I A (Fabricius). A genus of coleopterous 

 insects belonging to the section Tetrumera and family 

 Crioceridte, having the body oblong and depressed, 

 the antennae moderately long and of equal thickness 

 throughout, the posterior thighs often thickened and 

 toothed beneath, the jaws robust with two or three 

 acute terminal teeth, and the terminal joint of the 

 tarsi received between the lobes of the third joint. 

 These insects, of which there are upwards of twenty 

 British species, are of elegant form, and generally 

 ornamented with brilliant colours of a metallic kind. 

 They are also furnished with a silky down on the 

 under surface of the body, which is of service to them 

 by preventing them from sinking when they fall into 

 the water, upon the plants growing in which they re- 

 side often in considerable numbers. In the twelfth 

 number of the Magazine of Natural History is con- 

 tained an account of the discovery of the egg-shaped 

 transparent brown cases of one of the species con- 

 taining the perfect beetle, on the stems of Arundo 

 phragmites, close to the root, and immersed in the 

 water or mud. It is not, however, stated at what 

 period of the insect's existence these cases (which are 

 described as the winter quarters of the Donacia} were 

 constructed It might indeed be inferred from the 

 perfect beetles being found in them that they were 

 constructed by the beetles for their abode. But that 

 they were intended neither for permanent nor occa- 

 sional abodes is evident from the external habits of 

 the insects. They might perhaps indeed be supposed 

 to be constructed by the beetles for their winter 

 abodes, but, as Messrs. Kirby and Spence observe, 

 " it does not appear that any perfect insect has the 

 faculty of fabricating for itself a winter abode similar 

 to those formed of silk, &c. by some Iarva3. Schmid 

 indeed has mentioned finding Rhagium mordax and 

 Inquisitor (beetles nearly related to Donacia) in such 

 abodes, constructed, as he thought, of the inner bark of 

 trees ; but these, IHiger has suggested, were more 

 probably the deserted dwellings of lepidopterous 

 larva;, of which the beetles in question had taken 

 possession." The ciicumstance of the cases of the 

 Donacia being found at the root of the plants im- 

 mersed in the water is sufficient to prove that they 

 were not formed by the beetle, since it cannot be 



supposed that an insect living above the surface of 

 the water and constantly on the wing would select a 

 spot for its winter abode beneath the surface of the 

 water. It only therefore remains to regard these 

 cases as the production of the larvae, within which 

 the perfect beetles are transformed at an early period, 

 so as to take advantage of the first fine days of spring ; 

 and indeed Messrs. Kirby and Spence expressly state 

 " that amongst the larva? which enclose themselves in 

 silken cocoons are those of the brilliant beetles fre- 

 quenting aquatic plants, constituting the genus Donacia 

 [Fabricius), and that the case of D.fasciata is fastened 

 by one side to the roots or surculi of Typha latifulia ;" 

 and the following observations from the same authors 

 will perhaps be regarded as sufficient authority for 

 our regarding the larvae as the architects of the cells, 

 and at the same time for enabling us to account for 

 the disco very, of the perfect beetles in the winter: 

 Insects of the beetle tribe, especially such as undergo 

 their metamorphosis under ground, in the trunks of 

 trees, &c., are often a considerable time alter quitting 

 the puparium before their organs acquire the requisite 

 hardness to enable them to make their way to the 

 surface ; thus the newly disclosed imago of Cctonia 

 aurata remains a fortnight under the earth ; and that 

 of Lucanus cervus, according to lloesil, not less than 

 three weeks." 



One of the handsomest, and, at the same time, most 

 abundant species, is the D. Proteus, so named from 

 the endless variety of colours which it assumes, vary- 

 ing from a rich red to copper, purple, blue, green, 

 bronze, &c. It is to be met with upon plants in 

 ditches in almost every situation, and is about one 

 third of an inch long. There are about twenty other 

 British species. 



DON AX is the specific name of the arundo-donax 

 of Withering, a reed common in the south of Europe. 

 DORCUS (Macleay). A genus of stag- beetles 

 (Lucanidce'), distinguished by having the jaws but of 

 moderate size, the antennae terminated by a four-jointed 

 sub-perfoliated club, the head very broad, and the 

 upper lip distinct The only British species is the 

 small stag-beetle (Lucanus par allel&pipedus, Linnaeus), 

 which is about an inch long, a little more or less, and 

 of a black colour. It is found in decaying trees in 

 various parts of the country. 



DORIPPE (Fabricius). A curious genus of crus- 

 taceous animals belonging to the Brachyurous decapods, 

 or crabs, and to the section Notopoda of Latreille, so 

 named in consequence of two or four of the posterior 

 legs being rudimental and dorsal. The shell is of mi 

 ovoid form, truncate behind, the claws are very small, 

 and the four hind legs short and slender. There are 

 three Mediterranean species of crabs belonging to 

 this genus, of which the Cancer lanatus of Linnaeus is 

 the type. 



DORITIS, Fabricius; (PARNASSIUS, Latreille). A 

 handsome genus of butterflies (Lepidopte}-a diurnn], 

 differing from the true genus Papilio, Machaon, t-jr., 

 by having the palpi evident, in front of the head, and 

 composed of three distinct joints. The club of ihe 

 antennae is short. The females have a kind of cor- 

 neous pouch at the extremity of the abdomen'. The 

 caterpillars, like those of the true papiliones, have ilia 

 neck furnished with a retractile fleshy appendage, but 

 they differ from the majority of butterfly-caterpiliais 

 in constructing a cocoon, in which they are trans- 

 formed into chrysalides. The species, of which there 

 are but few in number, inhabit the mountainous dis- 



