330 



MUSEUM OF ANIMATED NATURE. 



[Arachxida. 



the limbs being visible. They endure with diffi- 

 culty the heat of the tun, and when stranded onen 

 bury theniM^lveii for shelter. Their food consists of 

 animal substances. Some are of very large size, 

 occasionally measuring upwards of two feel in 

 lentrth. The savajjes of the Moluccas are in the 

 habit of eniployiiiic the caudal spike as a weapon, 

 and a dreadful weapon it makes when ti\ed upon a 

 shaft. In China the eggs are esteemed a de- 

 bcacy. 



Fie. 3288 represents the Limulus Moluccanus 

 (L. PolyphemuK, Fabr.): a, the two simple eyes; 



6 A, the lateral eves of composite structure ; c, orifices 

 of respiration alone the abdominal buckler. It is 

 an inhabitant of the Indian seas, and must not be 

 conlounded with the Limulus Polyphemus, Kanz., 

 which is a native of the Atlantic along the coasts of 

 America and the Antilles. This latter is the P. 

 Americanus of Leach. There are other species, of 

 which one is the Limulus rutundicauda. Fig. 3l^i), 

 from the Moluccas : A, the animal seen from below ; 

 a, frontal portion of the carapace or buckler; 6, an- 

 terior feet ; c, second pair of feet ; d, sixth pair of 

 feet ; e, abdomen ; /, opercular plate formed by the 



two first false feet; tf, branchia. appendages; It, 

 caudal spike : B, one of the second pai.-^ of thoracic 

 jaw-limbs: C, one of the second pair of thoracic 

 limbs in the male of P. Moluccanus: D, one of the 

 branchiferuus false feet ; a, the branchial appendage • 

 E, the opercular plate seen on its internal surface, 

 showing the orifices of the egg tubes. 



Fossil specimens of extinct Limuli, some of great 

 size, occur in certain strata, as tlie iron-stone of the 

 coal formation, Colebrook Dale ; the lithographic 

 slate of Solenhofen and Pappenheim, the muschel- 

 kalk, &c. 



CLASS ARACHNIDA.— (SPIDERS AND SCORPIONS.) 



It has been the practice of many naturalists to 

 place the Arachnida within the pale of the Insecta, 

 or Insects; nevertheless, they present such import- 

 ant differences, both, as respects external form, 

 structure, and habits, as to Justify their separation 

 into a distinct class. 



In the first place, the Arachnida are utterly desti- 

 tute of wines ; and thoueh many insects are apterous, 

 yet apterous insects must be regarded as exceptions 

 referable to other orders, in which wings are general 

 characteristics. In the second place, they undergo 

 no true transformations; they have no larva or 

 caterpillar condition, but only experience a succes- 

 sion of moults, said by M. Jurine, fils, to be six in 

 number before attaining to their mature slate. 



Another important point is, that the head is not 

 separated, as in insects, from the thorax, but, as in the 

 higher Crustacea, coalesces with it, there being only 

 two great divisions of the body externally recog- 

 nisable instead of three. 



The eyes moreover are simple, and variable in 

 number, and the place of the antennae is taken either 

 by two jointed pincers or claws, which have erro- 

 neously been deemed identical with the mandibles 

 of Insects, or, as in spiders, by two pointed hooks or 

 fangs, for seizing and piercing prey. These claws 

 and fangs are called antenne-pmces, or antennae- 

 pincers, serres frontales, and chelicicres; and in 

 spiders, mandibles, by various authors. 



The limbs are usually eight in number, that is, 

 four on each side. In some species, however, the 

 number is six, and in others ten. 



Considered with respect to the nervous system, 

 the Arachnida differ from insects in the concentra- 

 tion of the ganglionic centres; this concentration 

 being carried in the former to a higher degree ; for 

 if the scorpions be excepted (which, in consequence 

 of the joints forming the abdomen, or tail, have an 

 extra number of ganglia), the ganglia of the double 

 nervous chord is at most three, and even in the scor- 

 pions it does not exceed seven. 



As respects the senses, the powers of vision are 

 acute ; and though we know not where the organ 

 of hearing is situated, we are assured that those 

 arachnida which from their size we can most easily 

 observe, are endowed with this faculty ; no doubt 

 the sense of taste is enjoyed in considerable perfec- 

 tion ; most are carnivorous and duly organised for a 

 life of rapine. Many species are parasitic, and of 

 minute size. While lately examining through a 

 lens the proboscis of a house-fly, we observed a mite 

 on the terminal sucking lips, bearing the same re- 

 lative proportions to the proboscis as the fly itself 

 would to the trunk of the elephant. These parasitic 

 Arachnida are suctorial. 



The Arachnida are divided into two great orders 

 or sections, according to the nature of their respira- 

 tory apparatus, viz. : — Pulmonaria and Trachcaria. 

 In Pulmonaria there are pulmonary sacs, in which 

 are branchise for aerial respiration, performing the 

 ofiice of lungs, and termed by Latieille Pneumo- 

 branchioe, or lung-gills. The heart is distinct. The 

 eyes from six to eight. The Trachearia differ in 

 having the respiratory organs in the form of air- 

 pipes, or trachese, like insects, ramifying through the 

 system, with two external orifices or stigmata ; there 

 is no distinct heart ; the eyes are from two to four. 

 In this order Latreille places the Pychnogonids, 

 which will be found among the Entomostracous 

 Crustacea: they have no tracheal stigmata. Set- 

 ting these aside, the Arachnida will arrange them- 

 selves as follows: — 



{Araneidse, or Spiders, 

 Phrynidae, Phrynus, 8cc. 

 Scorpionida;, Scorpions. 

 {PseudoscorpionidiE, Galeodes, &c. 

 Phalang'diE, bhepherd Spiders, 

 Acaridse, Mites, &c. 

 Spiders are divided into numerous genera, and 



indeed differ from each other materially in habits 

 and modes of life, in the arrangement of their webs, 

 and in their manner of capturing their insect prey. 

 All are venomous, at least to insects, and all display 

 ferocity, cunning, and address. Though not tolerated 

 as welcome guests in our rooms, these animals are by 

 no means really uninteresting ; — they are at great 

 pains to keep their downy limbs clean, passing them 

 through their mandibles to free them from dust ; 

 they are assiduous in repairing their broken webs; 

 they are patient in watching for their prey, and 

 daring and skilful in the attack, and they glide 

 along their filmy cordage with inimitable dexterity. 

 The females exceed the males in magnitude. 



By way of commencing our observations on these 

 well-known creatures, we may first direct our atten- 

 tion to the mandibles or 'serres frontales.' They 

 consist each of a stout basal joint, surmounted by a 

 moveable, sharp, hook-like weapon, capable of being 

 folded down or raised up ; this hook or tooth is per- 

 forated by a tube leading to a poison-sac, whence 

 exudes a deadly fluid, fatal to flies and the ordinary 

 prey upon which the spiders feed; this fluid is 

 thrown info the wound in the same manner as in 

 the case of venomous snakes. The part of the basal 

 joint against which they are folded is either fur- 

 nished with a brush of hair, or distinct serrations, 

 at least generally. Let us refer to Fig. 3290, in which 

 a represents the Red Spider (Dysdera erythrina), b, 

 is the head of this species magnified ; c, the man- 

 dibles, or 'serres frontales,' with a brush of hairs 

 against which the moveable fangs are folded ; d, the 

 eyes; e, represents the head of the Garden, or Geo- 

 metric spider (F,peira Diadema), a very common but 

 a very beautiful species, from its enamelled mark- 

 ings; g g, the fangs; /(, the serrated or comb-like 

 edge of the basal joint ; ///, the eyes. 



Externally to these mandibles are the maxillary 

 palpi, one on each side (see «, Fig. 3290), termina- 

 ting in the female in a simple point or hook ; but 

 in the males, of some species at least, if not all, they 

 are much more complex, and are capable of being 

 folded up. Fig. 3291 represents the male Garden 

 spider, with the palpi magnified. The eyes are 

 bright and distinct, and placed on the anterior part 

 of the cephalo-thorax. They are six or eight in 

 number, and arranged in a different manner in dif- 

 ferent genera. By consulting the figures a better 

 idea of their position will be formed than can be 

 expressed by words. Fig. 3292, Eyes of Mygale 

 avicularia: Fig. 3293, Mygale ca;mentaria: Fig. 

 3294, Lycosa vorax : Fig. 3295, Dolomedes margina- 

 tus: Fig. 3296, Ctenus dubius: Fig. 3297, Sphasus 

 Indianus . Fig. 3298, Attus pariis : Fig. 3299, Eresus 

 cinnabarinus : Fig. 3300, Thomisus citreus: Fig. 3301, 

 Clubiona accentuata : Fig. 3302, Dysdera erythrina : 

 Fig. 3303, Segestria perfida : Fig. 3304, Tegenaria 

 domestica: Fig. 3305, Epeira Diadema: Fig. 330G, 

 Thoridion coronatum : Fig. 3307, Latrodecta 13- 

 guttata: Fig. 3.308, Argyroneta aquatica. 



T"he limbs, four on each side, consist of seven 

 joints, two for the hips, one for the thigh, two for 

 the tibia, and two for the tarsus. The last tarsal 

 joint usually terminates in two hooks or claws with 

 comb-like dentations, and a straighter claw with a 

 saw-like edge. (Fig. 3:J09.) By means of this 

 structure the spider is able to glide along her lines, 

 to lay hold of her cordage, and shake her web, as 

 may be often witnessed, probably to try its security, 

 and. after ascending a line by which she has dropped 

 down from some elevation, to coil it up into a ball 

 and throw it away. .By means of this apparatus she 

 also cleans her own person, and brushes away the 

 dust from her network. 



Spiders have been celebrated in every age for 

 their webs, or filmy tissues, in which they entangle 

 their prey, or conceal themselves or their progeny 

 from observation. These webs are composed of 

 threads, the production of a curious apparatus, situ- 



[ ated under the abdomen, and called the spinneret. 

 These spinnerets are four, or more, mamraillary 

 processes, perforated by innumerable minute orifices, 

 through which are drawn thousands of separate 

 lines of a glutinous fluid, the product of certain ves- 

 sels, or secreting reservoirs, destined to furnish the 

 material: the lines quickly harden, and at a little 

 distance from the spinneret become united together, 

 and form a single cord composed of many thou- 

 sand parallel lines of inconceivable fineness. Fig. 

 3310 represents the spinnerets of a spider magnified, 

 to show the apertures, or spinnerules. Fig. 3311, v 

 the mode in which the threads are drawn out, but 

 each line represented contains about a hundred of 

 wonderful delicacy. Fig. 3312 shows the way in 

 which the lines all become united to form a single 

 cord. Fig. 3313 shows the Gaitlen spider, Epeira 

 Diadema, hanging by a thread. 



Of tuch delicate cordage then is the thread of the 

 spider constructed, and such the apparatus from 

 which 



" ilia remittit 



Stamen, ct antiqiuu exercet aiaiiea telas."— Ovid. 



Different as are the webs of spiders in their ar- 

 rangement, it is by me.ins of the claws that the 

 fibres are disposed in due order, and in this labour 

 the pectinated claws are most in requisition, the 

 serrated claw being used in rolling up waste threads, 

 to be rejected after the temporary purpose is served. 



The webs of spiders consist either of close tissues, 

 composed of threads crossing each other in various ' 

 directions, or open lace-work, in which the threads 

 are more or less symmetrically arranged, constitut- 

 ing nets of exquisite beauty. Among the artificers 

 which produce the former kind of manufacture may 

 be noticed the common House spider, Aranea do- ) 

 mestica. The webs of this spider are placed nearly 

 horizontally in the corners of rooms, among the rafi- . 

 ers of barns, stables, &c. : their construction is as 

 follows : — Having chosen the site, the spider fixes '• 

 the first thread, which is to form the selvage of the 

 tissue, to one of the walls, or some convenient point, 

 and, drawing out her thread all the time, she forth- 

 with proceeds to the opposite point, and there 

 fastens it. This process she repeats several times, 

 in order, by redoubling the threads, to give due ■' 

 strength to the margin. She next proceeds to draw • 

 threads in all directions, crossing and recrossing 

 them until, every interval being filled up, the web 

 exhibits an irregular gauze-like structure stretched 

 horizontally. It mostly happens that, in addition to 

 this web, there is an intermele of lines carried up 

 from its edges, so as to form a maze of cordage, so • 

 intricately blended as to prove a snare to the ram- 

 bling fly, for whose destruction they are spread. Thus . 

 is the web of the House spider arranged. But 

 where is the grim artificer? Patiently lurking in a 

 little hiding-place or chamber covered with a close 

 tissue of web, in a remote corner concealed from 

 view; but watching in her den the extent of her 

 toils spread before her. Leading to this den are a 

 number of threads, which, vibrating upon the en- 

 tanglement of the expected victim, inform the spider 1 j 

 of the booty within her grasp ; then instantly she 

 comes forth and pounces upon her struggling victim. 



Of the net weavers the Geometric spider of our 

 gardens, Epeira Diadema, is an example. Who 

 that has walked abroad on a fine autumnal morning 

 can have failed to notice the nets of radii and con- 

 centric circles fabricated by this artist ! The mode 

 in which the Geometric spider constructs her net is 

 not a little curious : the outline is first formed and 

 secured : then the radii ; and, when a_sufficient num- 

 ber of these are arranged, beginning at the centre, 

 she forms the concentric circles. From these nets, 

 which are placed vertically, lines extend to distant 

 objects, and are carried from branch to branch. 

 The mode of fixing these is not well understood. 

 According to Mr. Blackwall, the spiders shoot out 



