184 



A R A C H N I D A. 



in the greater part, and often beautifully coloured, 

 the colours fading almost instantly upon the death of 

 the bird. The bill of the aracari is never thicker 

 than the head, and seldom quite so thick, though it 

 is still a bill of very ample dimensions. It is regu- 

 larly curved in the culmen or ridge of the upper man- 

 dibie, both mandibles are slightly bent at the tip, 

 which is very sharp, and their tomia or cutting edges 

 are toothed or serrated. The plumage is in general 

 smooth, and the prevailing colours are green, marked 

 with red or yellow on the neck and breast, and the 

 green in some places passing into deep blue, and in 

 others into black. There are several species, but 

 they do not differ very materially in their appearance, 

 and little, if at all, in their manners. The following 

 figure will give a general idea of their form and the 

 manner in which thev sit on a branch. 



Curl Crested Aracari. 



These birds are all natives of the forests in the 

 warmer parts of South America. They extend from 

 Guiana to Paraguay, and also into Brazil ; but, except 

 South America, they are not met with in any other 

 part of the world. The British birds which they 

 most nearly resemble in their habits are magpies ; 

 but they are much less upon the ground, and more 

 exclusively tree birds. They are, however, about 

 the size of magpies, or, leaving out the great excess 

 of bill, perhaps a little smaller; and they are more 

 beautifully coloured. Though yoke-footed, they do 

 not run along and inhabit the bark of trees, like 

 woodpeckers, they fly with rather fluttering wings from 

 tree to tree, and leap with great adroitness from branch 

 to branch. In some respects they are omnivorous, 

 but, as is the case with most omnivorous birds, they 

 prefer animal food if they can obtain it. They live 

 much upon the larger insects and their larvte, and 

 they are also great plunderers of the nests of smaller 

 birds, eating with avidity either the eggs or the callow 

 young, though it does not appear that they ever at- 

 tack full-grown birds if in a state of vigorous health. 

 Their vision is quick, and though, from the great size 

 of the bill, the head cannot be jerked about so rapidly 

 as that of a magpie, they have a good deal of the 

 prying looks and peculiar habits of those thievish 

 birds. They reside more in the wild woods, how- 

 ever, and come not often into the neighbourhood of 

 human dwellings. Their colours are fine, and, though 

 their lives are not very honest, their motions are 

 often graceful ; but, like all the rest of the gaudy 

 climbing birds which inhabit the tropical forests, they 

 have little to boast of in their music; their croak, or 

 crash, or whatever else it may be called, is a single 

 screech, something resembling the caw of a rook cut 

 in two in the middle. 



ARACHNIDA, Mac Leay (Arachnites, Lamarck 

 and Latreille ; Arachnoida, Leach). A class of articu- 



lated animals, the name of which is derived from 

 Arachne,the name by which the spiders, which are the 

 chief species contained in it, were known to the Greeks. 

 The celebrated Cuvier, having by his invaluable dis- 

 coveries in the comparative anatomy of the invcrte- 

 brated animals, established the propriety of the removal 

 of the Crustacea, as a class, from the apterous insects of 

 Linnaeus, Aranea and the remaining genera (with the 

 exception of Pulex, as already noticed under the 

 article APTERA) were shortly afterwards raised to a 

 similar rank by Lamarck, under the name of Aruch- 

 nides, having been previously regarded as a distinct 

 order by Fabricius, under the name of Unogata, and 

 by Latreille under that of Accphala. Lamarck, 

 however, introduced into the class the centipedes, 

 millepedes, spring-tails, &c., under the name of 

 Arachnides antennistes, in addition to the spiders 

 and scorpions, or Arachnides palpistes. The class 

 has, however, been restricted by Latreille, Mac Leay, 

 and most modern entomologists, to the latter, the 

 former composing portion of the class Ametabola, or 

 Myriapoda. Thus constituted the Arachnida are 

 distinguished by their comparatively small size, their 

 bodies in general being short and rounded. They 

 consist of two parts only, the cephalo-thorax and ab- 

 domen, the head being so intimately united to the 

 thorax that scarely the slightest traces can be per- 

 ceived of their union : whilst in others even the 

 separation of the cephalo-thorax from the abdomen is 

 almost equally imperceptible. Like the Crustacea, 

 they are destitute of wings, and are not subject to 

 those metamorphoses which distinguish the true 

 insects. 



The organs of respiration, upon which great stress 

 has been laid as affording some of the primary 

 characters of the group, consist either of internal air 

 gills performing the office of lungs, and enclosed in 

 pouches, or of radiated trachea, the spiracles or pas- 

 sages for the entrance of the air being from two to 

 eight in number, and situated either at the lower 

 part of the abdomen or the sides of the cephalo- 

 thorax. 



Messrs. Kirby and Spence have adduced various 

 arguments of considerable weight against the union 

 in the same class of animals whose circulatory system 

 is so distinct as the trachean and pulmonary arach- 

 nida, and have considered the latter only as referable 

 to the class, placing the trachean species in the class 

 of insecta. Mr. Mac Leay, however, after a very 

 careful examination of the chief types of the class in 

 a living state, has defended, with his usual abilitj-, 

 the introduction of the trachean species into the 

 class, and observed, that these " most evident arach- 

 nida" have no relation with the hexapod ametabola. 

 See Zoological Journal, No. 18. 



The anterior part of the cephalo-thorax generally 

 exhibits on its upper surface a certain number of 

 minute shining points, which are the organs of sight ; 

 they vary in number from two to eight, and fur- 

 nish excellent characters for the distinction of the 

 generic groups. Unlike hexapod insects, the ani- 

 mals of this class are furnished with eight very 

 long legs, generally terminated by two small claws; 

 in front of the legs are to be observed a pair of 

 very powerful organs terminated by acute moveable 

 hooks, which, in many cases, afford passages for 

 the discharge of that poisonous fluid with which 

 some of the insects are provided. These organs 

 have been termed chelicera, by Latreille, who consi- 



