544
arachnida
remarkable group has reference to the position of the male mtroFm 75.—Cryptostemma Karschii, one of the Podogona. Ventral view. I to VI, the six pairs of appendages of the prosoma, the last three cut short; 1, 2, 3, 4, the four somites of the opisthosoma ; a, hood overhanging the first pair of appendages; 6, position of the genital orifice; c, part of 3rd appendage; d, fourth segment of 2nd appendage. Observe that the basal segment of appendage III does not meet its fellow in the middle line. (Original drawing by Pocock and PickardCambridge.)
Sub-order c. Anepignathi.—Basal segments of appendages of 2nd pair meeting in the middle line across the area that lies between the mouth below and the basal segments of the appendages of the 1st pair above, to the partial or total exclusion of the unpaired skeletal pieces, known as the clypeus and labrum. Genital orifice lying between the basal segments of the appendages of the 6th pair and separated from the mouth by a relatively long space occupied by the inner extremities of the basal segments of the 3rd, 4th, Fig. 77.—Stylocdlus sumatranus, one of the Opiliones ; after Thorell. Enlarged. A, dorsal view; I to VI, the six prosomatic appendages ; B, ventral view of the prosoma and of the first somite of the opisthosoma, with the appendages I to VI cut off at the base ; a, tracheal stigma; mx, maxillary processes of the coxa? of the third pair of appendages ; g, genital aperture. C, ventral surface of the prosoma and opisthosoma; a, tracheal stigma ; ft, last somite. D, lateral view of the first and second pair of appendages. E, lateral view of the whole body and two first appendages, showing the fusion of the dorsal elements of the prosoma into a single plate, and of those of the opisthosoma into an imperfectly segmented plate continuous with that of the prosoma. 5th, and 6th pairs of appendages, the sternal sclerites being evanescent. Appendages of 2nd-6th pairs short and strong, furnished with a single claw. , 77 7, , Family—Gyphophthalmidae (Cyphophthalmus, Styloceuus, 1 ettalus). . , TT Remarks on the Opiliones. — These include the Harvest-men, sometimes called also Daddy-long-legs, with round undivided bodies and very long, easily-detached legs. The intromittent organs of the male are remarkable for their complexity and elaboration Ihe confluence of the regions of the body and the dislocation ot apertures from their typical position are results of degeneration. Ihe Opiliones seem to lead on from the Spiders to the Mites. Reference to literature (39). . , ^ „ , Order 9. Rhynchostomi = Acan (see Fig. 78). Degenerate Arachnids resembling the Opiliones in many structural points,, but chiefly distinguishable from them by the following features The basal segments of the appendages of the 2nd pair are united in the middle line behind the mouth ; those of the 3rd, 4th, 5th, and 6th pairs are widely separated and not provided with sterno-coxal (maxillary) lobes, and take no share in mastication ; the respiratory stigmata, when present, belong to the prosoma, and the primitive segmentation of the opisthosoma has entirely or almost entirely
mittent organ (Fig. 73, e). They are small degenerate animals with a relatively firm integument. Not more than four species and twice that number ol specimens are known. They have been found in West Africa, and South America. A fact ot special interest in regard to them is that the genus Anthracomartus, from the Coal Measures, appears to be a member of the same group, ihe name Cryptostemma, given to the first-known genus of the order, described by Guerm-Meneville refers to the supposed concealment ol tne eyes by the movable cephalic sclerite. Reference Fig. 76. — Cryptoto literature (38). . , stemma Karschii. Order 8. Opiliones (see Fig. 77).—Dorsal area Extremity of the pair of apof prosoma covered by a single shield bearing a fifth pendages of the pair of median eyes, or one or two pairs ol lateral female for comeyes. Sternal elements much reduced. Append- parison with that ages of 1st pair large, three segmented, and com- of the male E in pletely chelate ; of 2nd pair either simple and Fig. 73. pediform, or prehensile and subchelate; of re. maining four pairs, similar in form, ambulatory m function. Mouth lying far back, the basal segment of the 2nd, 3rd and sometimes of the 4th pairs of appendages furnished with sternocoxal (maxillary) lobe. Opisthosoma confluent throughout its breadth with the prosoma, with the dorsal plate of which its anterior tergal plates are more or less confluent; nine opisthosomatic somites traceable ; the generative aperture thrust far forwards between the basal segments of the 6th or 5th and 6th appendages. Pree-genital somite suppressed. Respiratory organs, tracheal openino- bv a pair of stigmata situated immediately behind the ba,sal segments of the 6th pair of appendages on what is probably the sternum of the 3rd opisthosomatic somite, and also m some cases upon the 5th segment of the legs. Intromittent organ of male lying within the genital orifice. Sub-order a. Laniatores.—The area between the mouth below and the basal segments of the appendages of the 1st pair above occupied by two unpaired skeletal pieces, tlie clypeus and labrum. Sternal area of prosoma occupied by a relatively long and very narrow sclerite, composed of prosternal and metasternal elements, and lying between the coxse of the appendages of the 5th pair,aand interposing between the mouth and generative orifice ; the l 'lter lodged between the basal segments of the appendages of the 6th° pair. Appendages of 2nd pair strong, generally spiny, and armed with a powerful claw. Appendages of 3rd and 4th pairs armed with a single claw; those of 5th and 6th with two claws. Sterno-coxal process of 3rd pair of appendages coalesced with the basal segment; that of the 4th pair not or scarcely developed. Principal families—Gonyleptidse (Gonyleptcs, Goniosoma). Biantidse (Biantes). Epedanidse (Epedanus, Acrobunus). Assamiidse (Assamia, Pygoplus). Oncopodidse (Oncopus, Pelitnus). Cosmetidse (Cosmetus). Sub-order 6. Palpatores.—Resembling the Laniatores, but with the sternal area of prosoma very short, the metasternal sclerite represented by a short transverse plate more or less overlapped by the forwardly-projecting sternal element of the opisthosoma that covers the genital orifice and intervenes between the basal segments of the appendages of the 5th and 6th pairs. The genital ortfice thus lies far forwards, close behind the mouth and on a level with the space between the basal segments of the appendages of the 5th pair. Appendages of 2nd pair small, weak, in no sense prehensile, unspined, the-claw weak or absent; the 3rd-6th pairs of appendages armed with a single claw. Sterno-coxal process of 3rd appendage movably articulated ; a similar lobe generally present on basal segment of 4th appendage. Principal families—Phalangiidae (Phalangium, Liobunun). Nemastomidse (Nemastoma, Ischyropsalis). Trogulidse (Trogulus, Anelasmocephalus).
^SubmrdCT a. Cryptostigmata.—Integxxmznt hard, strengthened by a continuously chitinized dorsal and ventral sclerite. Iracheae typically opening by stigmata situated in the articular sockets (acetabula) of the 3rd, 4th, 5th, and 6th pairs of appendages. Family—Oribatidse {Oribata, Nothrus, Hoplophora). Sub-order b. Metastigmata.—Integument mostly like that of the Cryptostigmata. Tracheal opening by a pair of stigmata situated above and behind the base of the 4th or 5th or 6th pair of appendages. _ , . Families—Gamasidse {Gamasus, Pteroptus). Argasidse (Argos, Ornithodoros). Ixodidfe (Ixodes, Rhipicephalus). Sub-order c Prostigmata.—Integument soft, strengthened by special sclerites, those on the ventral surface of the prosoma apparently representing the basal segments of the legs embedded m the skin. Tracheae, except in the aquatic species in which they are atrophied, opening by a pair of stigmata situated close to or above the base of the appendages of the 1st pair (mandibles). Families—Trombidiidse (Trombidium, Tetranychus). Hydrachnidse (Hydrachna, Atax). Halacaridse (HalacarusuLeptognathus). Bdellidae (Bdella, Eupodes). Sub-order d. A stigmata. — Degenerate, mostly parasitic forms approaching the Prostigmata in the development of mtegumental sclerites and the softness of the skin, but with the respiratory system absent. . Families—Tyroglyphidse (Tyroglyphus, Rhizoglyphus). Sarcoptidse (Sarcoptes, Analges). Sub-order e. Vermiformia. — Degenerate atracheate parasitic
