STRUCTURE, FUNCTIONS AND CEOONOMY OF ARANEIDEA. 6'J 



are of the utmost consequence, as they do not construct snares, but capture 

 their prey by springing suddenly upon it from a distance, have the terminal 

 joint of the palpi abundantly supplied with hairs, and constantly make use of 

 those organs as brushes to remove dust, or any other extraneous matter, from 

 the corneous coat of the anterior eyes. 



The palpi appear to afford direct assistance likewise to spiders in general 

 in securing their prey, in changing its position while they are feeding upon 

 it, and in restraining the action of the wings of all their victims which happen 

 to be provided with them*. 



With regard to the function exercised by the remarkable organs connected 

 with the digital joint of the palpi of male spiders there exists some difference 

 of opinion. Taking anatomy as his guide, Treviranus arrived at the conclu- 

 sion that the parts in question are used for the purpose of excitation merely, 

 preparatory to the actual union of the sexes by means of appropriate organs 

 situated near the anterior part of the inferior region of the abdomen. This 

 view of the subject, whicli is very generally adopted, is opposed to that de- 

 rived from physiological facts by Dr Lister and the earlier systematic writers 

 on arachnology, who regarded the palpal organs as strictly sexual. 



Rejecting the opinion of Treviranus, Baron Walckenaer has given his sup- 

 port to that entertained by Lister and the physiologists, having endeavoured 

 to establish its accuracy by pursuing the imperfect method of investigation 

 employed by the latter, which chiefly consists in examining the condition of 

 the palpal organs when applied by male spiders to the vulva of females and 

 carefully noticing the changes they undergo ; but as it is possible that such 

 females, should they prove to be prolific, may have been impregnated at a 

 former period, and as other organs than those connected with the digital joint 

 of the palpi may have been instrumental in producing the result, observations 

 of this description appear to be quite inadequate to effect the object proposed. 



An attempt to relieve the inquiry from objections so weighty is recorded 

 in the ' Report of the Third Meeting of the British Association for the Ad- 

 vancement of Science, held at Cambridge in 1833,' pp. 444-5, and the result 

 arrived at has a direct tendency to confirm the truth of the opinion promulgated 

 by Dr. Lister. Since that time, researches in connexion with this subject have 

 been greatly extended and varied, and it is satisfactory to add, that they sup- 

 ply a body of evidence which appears to be conclusive as to the agency of 

 the palpal organs. 



The following is a concise summary of the more important particulars 

 elicited by this investigation. 



It is an admitted fact, that female Aphides, when impregnated, are capable 

 of producing females which, without sexual intercourse, are prolific through 

 several successive generations. In order to determine whether this is the 

 case with spiders or not, young females of the species Tegenaria domestica, 

 Tegenaria civilis, Agelena labyrinthica, Ciniflo atrox, Drassus sericeus, Theri- 

 dion quadripunctatum, Segestria senoculata, &c., were placed in phials of 

 transparent glass and fed with insects. Most of these individuals remained 

 in captivity from one to three years after they had completed their moulting 

 and attained maturity ; yet three only, an Agelena labyrinthica, a Tegenaria 

 domestica, and a Tegenaria civilis, produced eggs, and they proved to be sterile, 

 though several of the others, to which adult males were subsequently intro- 

 duced, laid prolific eggs after coition. It is worthy of remark, that the spiders 

 which produced unfruitful eggs deposited them in cocoons and bestowed the 

 same care upon them as if they had been fertile. 



* Report of the Twelfth Meeting of the British Association for the Advancement of Science, 

 held at Manchester in 1842 ; Transactions of the Sections, pp. 67, 08. 



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