Behind the cejihalic lobe are the true somites, beginning with the somite of the chelicerae (A. The similar position of the arachnid chelicerae and the crustacean second antennae on the head.
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NO. 10 FEEDTNG ORGANS OK AKACH NIOA— SNODGRASS II
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THE PALPIGRADI, OR MICROTHELYPHONID.\
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The leg-like second appendages, which correspond to the pedipalps of other arachnids, lie entirely behind the mouth (D. l'df>) and are connected to a large ventral plate (II+IIIS) that appears to be a combination of the deutosternum and it is the tritosternum, as it bears both the second and third pairs of appendages. The mouth cone of the I'alpigradi suggests the proboscis of the I'ycnogonida, which extends below the chelicerae and between the pedipalps. but the jK'dipaljJS arise, as in the I'alpigradi. of a sternal plate behind the base of the proboscis.
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THE SOLPUGIDA
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THE PEDIPALPIDA
The dorsal clitoral muscles of the pharynx originate on the epistonial apodeme, the lateral dilators originate on the coxal apodeme (A, Phy). Due to the independence of the pedipalp coxae and the small size of the labrum. cxp Chi. h) IICx Mbh.
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The lower surface of the cucullus bears a median rim that separates lateral concavities that fit over the chelicerae, whicli structure, as noted by Hansen and Sorensen (1904). The segmentation of the pedipalp (E) is simple compared to that of the legs (B), there are two trochanteral segments (iTr, 2Tr) as in the legs, but the tibia is a long, slender segment (Tb) and the tarsus {Tar ) forms the small movable finger of the chela. IIOcoxal via the round labrum (C,Lm), which is supported by a coxal via the round labrum (C,Lm), which is supported by a large epistomal plate (Epst), united laterally with the dorsal walls of the adjacent parts of the pedipalp coxae.
The chelicerae (Chi) are small, two-segmented, and project straight forward from under the edge of the carapace. The coxae themselves thus replace the sterna and become the actual ventral exoskeleton of the prosoma.
34 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, II called serridae, and finally they are the seat of important sense
The lateral dilator muscles (dll), inserted on the lateral walls of the pharynx, originate from the lateral walls of the pedipalp coxae. Tafrognath could be compared to the lamina dorsalis of the passage of food in. Thelyphonidae, but the lophognath is not comparable with the lamina ventralis, and the pouch pharynx of the chelonetid is quite distinct from the preoral part of the alimentary apparatus.
Lifting the taphrognath from the lophognath by contracting the dorsal muscles (Fig. 12F) would pull. There is the usual association of the chelicerae, labrum and pedijalp coxae, but on the lower lip of the scorpion.
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The pedipalp coxae are completely separated from each other, and there is no recognizable remnant of the pedipalp sternum in the scorpion. The pharynx of the scorpion is a small, pear-shaped sac that enlarges upward and posteriorly from its constricted outlet at the mouth. The dorsal wall of the sac is deeply folded and the trough of the intussusception is.
The base of the stinger is articulated at the end of the supporting segment in such a. The dorsal muscles are widely varied but both are inserted on a strong dorsal process of the sting base.
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10 FKEDING ORGANS OF ARACIINMnA SNODORAS.- 45 . is a large open space, the so-called stoomka, in which the endites of the i)Cflipalps and the first bones (I) are contained. Posteriorly, the stoniotheca is closed by the apyroxinated inner tips of the second leg coxae (IVCx), on which are rounded elevations of an endite. 15.—Phalangida-Cypliophthalini, Holosiro acaroidcs Ewiiig. When the coxae are detached from the second legs and viewed from behind (G), the endites are seen as distinct lobes, although their surfaces are hard and not membranous.
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10 KKEDINT, OKC.ANS OF AKAClINIDA— SNODGRASS 49 those of the first legs opening centrally on the inner surfaces. The entrance to the mouth of Phalatujium opilio I., is described by Kastner (1933a, 1935) as a short funnel with its walls thrown out into six radiating folds. Kastner says that the mouth can be closed by the first circular muscles of the pharynx immediately behind it.
The pscudotraclieal canals of the pedipalp endites (Fig. 16 E, c) open into the lumens of the lateral oral folds. The pharynx of Phalangium opilio is raised vertically from the mouth by Kastner and then suddenly rotated posteriorly into a narrowed horizontal part; in the figure of the police of the same kind, the distinction between the two parts is much less accentuated.
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Then, while one of the pincers holds the cut edge, the other reaches into the opening and pulls out pieces of the entrails and brings them to the mouthparts. The pedipalp coxae, except in the Liphistiidae and most of the Mygalomorphac, have large distal processes that usually form strong but immovable jaw-like lobes. The dorsal plate is traversed by a median canal that runs forward from the opening of the esophagus.
In the Mygalomorphac the gland is wholly or chiefly contained within the basal segment of the chelicera; in other groups it may project into the body cavity as far as or beyond the prosomatic nerve mass. The gland is covered by a layer of muscular fibres: the filaments are said by Millot (1931) to be generally arranged spirally along the length of the sac, but present variations and irregularities.
52 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IIO Glands contained in the pedipalp coxae and opening into the preoral
Kastner observes that during feeding the rapid extension and contraction of the labrum in the alimentary canal apparently exerts a transoral suction action on the alimentary fluid. Bertkau (1885) demonstrated experimentally that the secretion of pedipalp glands has a dissolving effect on the muscles of the fly. Lipase is strongly present, and in some cases amylase, but probably only amylase comes from the prey.
The claws provided the usual two pretarsal muscles, a levator arising in the tarsus and a depressor arising in the tibia. and the patella with its fibers inserted on a long ventral tendon in the claw. The pedipalp coxae lie horizontally in the plane of the bencoxae, but they diverge anteriorly from the suboral sternum between their bases.
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The relatively weak, concave ventral plate of the pharynx (Fig. .. 19E) is longer than the dorsal plate because the edge of the pedipalp sternum (US) extends beyond the labrum. On the inner end of the abdominal plate is inserted a pair of large muscles from the prosomatic shield (l'>). These coxal lobes of the spiders have no independent movement, as they are firmly attached to the coxae.
Apparently they suggest the coxal endites of the Phalangida, but in so far as they arise from the distal ends of the coxae, and i. 58 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, 110usual anterior coxal processes, such as those typical of Mygalo-.
58 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, 1 10 usual anterior coxal processes, such as those typical of the Mygalo-
THE ACARINA
Laterally, the tectum is fused with the dorsally expanded basal angles of the pedipalp coxae (IICx). The ventral wall of the capitulum is made below the mouth and labrvun as a. The composition of the capitulum according to Schulze (Fig. 22D, E) is as follows: Pedipalp coxae ("Maxillae") form the greater part of the basal capitulum (Collare or Kragen), but usually the trochanters must be included, from the indeterminate hooks they appear as separate basal segments of the palps ( Fig. 26E, t).
At the base of each coxal lobe of the hypostome are seen the processes cymatii (E, pc), and on the side of this is a saddle-like part, the "sella" {s), representing the small fold above the cymatium of the primitive coxa (C, pp). Finally, a sub-coxal component is present as an invaginated extension from the base of the capitulum (D, E, sc).
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34;maxillary lobe"; the inner (/') is a thin lamella, which we refer to as the "maxillary plate". The palps of the notostigmatid pedi)alps are four-parted beyond the coxa and each bears a pair of prctarsal claws. Proximal to the capitulum j^rojecls from the ventral surface of the body the median bifid process (Fig. 23 E, t), which is apparently a secondary development on the thoracic region of the first leg segment, A in Fig. 24 shows an extremely generalized condition of the mouthparts combined with a well-developed capitulum.
The ventral wall of the capitulum projects beyond the mouth (Mth) and forms a short structure below the lip or hypostome (Hst) with a median sul>oral lobe and a pair of lateral lobes. If this is a true picture of the structure of an oribatid, the latter is characteristically arachnoid except for the presence of a long dorsal wall of the capitulum.
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The lower wall of the capitulum of Ilolothyrus (fig. 24 D) has a three-lobcd apj^earing due to indentations longitudinally along the sides (E, V). A subcheliceral epistonial plate is clearly depicted in cross-section, which provides attachment to the dorsal muscles of the pharynx. The ventral wall of the capitulum (B, C) is expanded between the i)alps to form the large hypostome (B,Hst), which may be parallel-sided, somewhat siwon-shajx-d, and.
However, in Dermacentor the apparent basal segment of the palp (C) is motionless united with the second segment, and in Boopliilus (G) one basal segment is indistinguishable from the second. Finally, the end of the cheliceral shaft is formed into a cap-like protective lobe (h) on the mesal side of the finger.
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The sulKheJiceral plate of the tick is evidently the epistome (Fig. 2j, lip), since it supports the labrum (^"t) at its distal end and gives attachment on its ventral surface to the dorsal dilator muscles of the pharynx (did) The basal lobe overhangs the mouth; the apical leaf, which varies in length in different species, lies above the groove of the hypostome. In Dcrmaccntorvariabilis, towinglikc plates diverge laterally and backwards from the anterior end of the pharynx at the base of the labrum (Fig. 28 D).
Andre (1927) states that the chigger grips the surface of the host with its palps, then squeezes the cheliceral. The dorsal surface of the epistome is deeply grooved to form a channel in which the chliceral stylets slide back and forth.
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On the other hand, the main movements of the stylets must be produced by protraction and retraction of the stylophore. The stylophore is capable of complete retraction under the marginal fold of the back that normally covers its basal half. The mouth lies within the tip of the rostrum (Fig. 29B, Mth) and opens directly into the pharynx (Phy).
Exactly why the spiracles should be in a place as uncomfortable as the infolded membrane at the base of the united chelicerae. Blauvelt notes that the long, slit-like peritremes of Tetranychus allow the spiracles to access the outside air at allusual positions of the chelicerae.
The structure of the capiluhim in Ornithodoros: a contribution to the study of the feeding mechanism in ticks.
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On the Nests of the Pseudoscorpioiis: With Historical Notes on the Spinning Organs and Observations on the Construction and Spinning of Nests. On some points of the anatomy of the digestive and nervous systems of arachnids of the suborder Pedipalpi.
92 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 10 Reuter, E
