Savory - Arachnida 1977

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32 II. DE ARACHNIDIS 4. PHYSIOLOGY: INTERNAL ORGANS 33 Fw. 7. Fore-gut of a spider. (i) Oesophagus and stomach of Araneus; (ii) oesophagus of Tegenaria. Filtering of the imbibed nutrients occurs in spiders in the pharynx; in scorpions in the channel between the long maxillary processes of the first two pairs oflegs; in the Opiliones there is no filtering. The pedipalpal coxae, which contain the maxillary glands in spiders, pia y no part in feeding in Scorpiones, Pseudoscorpiones or Solifugat:. In general, the prey, held in the chelicerae, is drenched by the salivary juices from the glands just mentioned, and the solution resulting from this external digestion is suck
34 II. DE ARACHNlDIS curved. It often includes a dilated portion, the stercoral pocket, in which faecal matter and excreta temporarily accumulate. Among Arachnida there are two types of respiratory organs or oxidizing devices, known as book-lungs (or lung-books) and tracheae. There are therefore four kinds of respiratory equipment, constituted of either or both or neither of these devices. Tracheae alone are found in Pseudoscorpiones, Solifugae, Opiliones, Ricinulei and Acari: the scorpions, uropygi and Amblypygi have booklungs only; a few families of spiders have tracheae only, but most spiders possess organs of both kinds; the small Palpigradi, the Cyphophthalmi and some of the Acari have only cutaneous respiration. The two systems received exhaustive study from Levi ( 1967). He pointed out that the tracheae are of two kinds, sieve tracheae and tube tracheae. The former exist in bundles that arise from a tubular origin on the eighth somite, the position alternatively occupied by the anterior pair of book-lungs. They are found in pseudoscorpions, Ricinulei and in some spiders. Tube tracheae are usually unbranched and are present in Opiliones, Solifugae and in most spiders. It is evident that book-lungs and tracheae are homologous, both being formed by ectodermal invagination. \'Vherever a tracheal system is elaborate it is probably more efficient than book-lungs, as is shown by their sole presence in Solifugae, the most active of all Arachnida, and in the active Opiliones, which may also have tracheal openings on the legs. vVhen book-lungs are formed by invagination, they develop a number of folds on the anterior surface, which project into the lung cavity and thus roughly resemble the leaves of a book (Fig. 9). There are one, two or four pairs oflungs, always situated in the anterior part of the opisthosoma. There are no respiratory movements; air enters the pulmonary spiracles and reaches the blood through the delicate epithelium of the leaves. The number of leaves ranges from about five to about 150. Species with many tracheae have fewer leaves. FIG. 9. Diagram of a book-lung, showing only four leaves. 4. PHYSIOLOGY: INTERNAL ORGANS 35 The following notes may be added to the above statements. Scorpions all have the full provision of eight book-lungs, yet they have so small a need for oxygen that seven of these can be plugged or sealed without apparent effect. In spiders the relative deHlopment of lungs and tracheae is very different in the different families, and does not seem to be related to the mode of life. The simple idea that great activity demands a copious supply of oxygen does not seem to be supported. Yet in the Solifugac there is a greater elaboration of the tracheae than in any other arachnid. There are three pairs cf spiracles, one of which is in the prosoma, and in one family there is an additional median spiracle in the posterior part of the opisthosoma. The tracheae themselves are wider, proportionately, than those of other Arachnida and they branch copiously throughout the entire body, appearing almost to have a segmental pattern. The spiracles are provided with muscles by which they can be opened or closed. In all, there seems to be no reason for not associating this unusual system with the greater speed with which the Solifugae are at times inclined to move. The blood or haemolymph of an arachnid is an almost colourless fluid in which corpuscles of three kinds are to be seen. There are small clear leucocytcs of a basophile character, some larger hyaline phagocytes and also large acidophile granular leucocytes. In spiders and scorpions the fluid itself is poisonous and can kill small mammals when it is injected into them. The heart (Fig. 10) is tubular and lies in a pericardium in the middorsal line of the opisthosoma. In Cropygi and Solifugae a part of it extends forwards into the cephalothorax. The blood runs forwards in a single anterior artery and backwards in three posterior arteries, and after passing through the smaller ,·essels, reaches the book-lungs. Aerated, it collects in a ventral sinus and so re-enters the pericardium through ostia that are closed bv valves. The number of the cardiac ostia varies from one to nine pairs. Contracting ligaments effect the pulsating of the heart, which in scorpions may beat from 60 to 150 times a minute. The heart of a scorpion is larger and the vascular system more fully developed than in the other orders; it is much reduced in the Solifugae, in correspondence with the great dependence on tracheal respiration. In Opilioncs it is short and has only two pairs of ostia. Among spiders the development of the heart and the number of pericardial ostia is more variable than in any other order, and Petrunkevitch has used this character as an important feature in the classification of the group. The nervous system in Arachnida follows a pattern familiar in other classes of Arthropoda. It consists of a cerebral mass united by circumoesophageal commissures to a ,·entral nerve cord, which primiti,·ely
Page 1 and 2: Arachnida THEODORE SAVORY 2nd editi
Page 3 and 4: Contents Preface Acknowledgements .
Page 5 and 6: MAIAE CARISSIMAE UXORI SECUNDAE LIB
Page 7 and 8: 1 The Phylum Arthropoda The phylum
Page 9 and 10: 6 I PROLEGOMENA The comparison impl
Page 11 and 12: 10 I. PROLEGOME);A one time so rare
Page 13 and 14: 14 I. PROLEGOMENA The most striking
Page 15 and 16: 18 U. DE ARACHNIDIS it, move to a f
Page 17 and 18: 3. MORPHOLOGY: EXTERNAL APPEARANCE
Page 19 and 20: 26 II. DE ARACHNIDIS 3. MORPHOLOGY;
Page 21: 30 II. DE ARACHNIDIS yet arachnolog
Page 25 and 26: 38 II. DE ARACHNIDIS 4. PHYSIOLOGY:
Page 27 and 28: 42 II. DE ARACHNIDIS fibres run upw
Page 29 and 30: 46 II. DE ARACH~IDIS As a rule the
Page 31 and 32: 50 11. DE ARACHNIDIS (iii) Inversio
Page 33 and 34: 54 II. DE ARACHNIDIS FIG. 21. Newly
Page 35 and 36: 58 II. DE ARACHNIDIS Pseudoscorpion
Page 37 and 38: 62 11. DE ARACHNIDIS of the exoskel
Page 39 and 40: 66 II. DE ARACHNIDIS Sometimes the
Page 41 and 42: 70 II. DE ARACHNIDIS using a scanni
Page 43 and 44: 74 II. DE ARACHNIDIS constitutes th
Page 45 and 46: 78 II. DE ARACHNIDIS think of Arach
Page 47 and 48: 82 II. DE ARACH::-.;IDIS declined t
Page 49 and 50: 86 II. DE ARACHNIDIS .Man is the on
Page 51 and 52: 90 11. DE ARACHNIDIS Autecology con
Page 53 and 54: 11. PHYLOGENY: EVOLUTION 95 11 Phyl
Page 55 and 56: 98 II. DE ARACHNIDIS An obvious ass
Page 57 and 58: 102 II. DE ARACHNIDIS start preserv
Page 59 and 60: 106 II. DE ARACHNIDIS Here are thre
Page 61 and 62: 110 11. DE ARACHNIDIS Araneae, and
Page 63 and 64: 13 The Order Scorpiones [Scorpionid
Page 65 and 66: 118 Ill. PROLES ARACHNES 13. THE OR
Page 67 and 68: 122 III. PROLES ARACHNES CLASSIFICA
Page 69 and 70: 126 III. PROLES ARACHNES 14. THE OR
Page 71 and 72: 130 Ill. PROLES ARACHXES The lowly
Page 73 and 74:
134 Ill. PROLES ARACHNES to be seen
Page 75 and 76:
16. THE ORDER SCHIZOMIDA 139 16 The
Page 77 and 78:
142 Ill. PROLES ARACHKES power, an
Page 79 and 80:
146 III. PROLES ARACHNES DISTRIBUTI
Page 81 and 82:
150 III. PROLES ARACHNES chelicerae
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154 Ill. PROLES ARACHNES FIG. 53. S
Page 85 and 86:
158 Ill. PROLES ARACHNES (vi) Lobed
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162 III. PROLES ARACHNES is found i
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166 III. PROLES ARACHNES 4 (3) Chel
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20. THE ORDER TRIGONOTARBI 171 20 T
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174 Ill. PROLES ARACHNES 22 The Ord
Page 95 and 96:
178 III. PROLES ARACHNES The family
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182 III. PROLES ARACHNES are above
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186 Ill. PROLES ARACHNES opisthosom
Page 101 and 102:
190 Ill. PROLES ARACHNES Sub-order
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194 III. PROLES ARACIINES 25. THE O
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26 The Order Acari 26. THE ORDER AC
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202 III. PROLES ARACHNES Tetrastigm
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206 Ill. PROLES ARACHNES 26. THE'.
Page 111 and 112:
210 Ill. PROLES ARACHNES ( 1) Notos
Page 113 and 114:
214 Ill. PROLES ARACHNES The sevent
Page 115 and 116:
218 Ill. PROLES ARACHNES family, Ho
Page 117 and 118:
222 Ill. PROLES ARACHNES posterior
Page 119 and 120:
226 III. PROLES ARACHNES 28. THE OR
Page 121 and 122:
230 Ill. PROLES ARACHNES From the f
Page 123 and 124:
234 Ill. PROLES ARACHNES 29. THE OR
Page 125 and 126:
238 Ill. PROLES ARACHNES The chelic
Page 127 and 128:
242 IlL PROLES ARACHNES 29. THE ORD
Page 129 and 130:
30 Economic Arachnology The Arachni
Page 131 and 132:
250 IV. DE ARACHNOLOGIA Although th
Page 133 and 134:
··~~- -..... 254 IV. DE ARACHNOLO
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31 Historical Arachnology The histo
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262 IV. DE ARACHNOLOGIA spiders qui
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266 IV. DE ARACHNOLOGIA little was
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32 Practical Arachnology The practi
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274 IV. DE ARACHNOLOGIA hard. In th
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278 IV. DE ARACHNOLOGIA EXCURSUS A
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33 Chemical Arachnology In the stud
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286 IV. DE ARACHNOLOGIA not very pl
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290 IV. DE ARACHNOLOGIA seventeenth
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294 IV. DE ARACHNOLOGIA A new aspec
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298 IV. DE ARACHNOLOGIA For more th
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36 The Spider's Web The webs that s
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306 V. HETEROGRAPHIA a number ofver
Page 161 and 162:
310 V. HETEROGRAPHIA dramatically p
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314 ( i) ( ii) ( iii) (iv) (v) V. H
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318 V. HETEROGRAPHIA this may be ad
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322 V. HETEROGRAPHlA .1\Jenge in 18
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326 VI. EPILEGO:VIENA Vellard, J.,
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i 330 Vl. EPILEGO~iENA Lamoral, B.
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334 VI. EPILEGOMENA Ill. Bibliograp
Page 175 and 176:
INDEX ANIMALIUM 339 Index Animalium
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Savory - Arachnida 1977

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