356 



NATURE 



[February lo, 1898 



STRIDULATION IN SOME AFRICAN 

 SMDERSy 



T^HE spiders which form the subject-matter of this paper, are 

 probably best known by the comprehensive title " Mygale." 

 They are also sometimes called crab-spiders, presumably from 

 the great size to which most of the species attain ; sometimes 

 bird-eating spiders, from their alleged propensity for capturing 

 and devouring small birds, a propensity which suggested to 

 Lamarck the generic term Avictilaria, still in use for one of the 

 South American genera. But during the last fifty years our 

 knowledge of this group has increased by leaps and bounds ; the 

 genus has expanded into a family, represented by numbers of 

 genera which are rapidly becoming more and more accurately 

 defined and classified. 



Apart from their large size and usually heavy build, these 

 spiders, referred to a family variously termed MygalidcE, 

 TheraphosidcB and Avictilariuitc, may be recognised from the 

 vast majority of other spiders by possessing two pairs of lung- 

 sacs, and by the circumstance that the mandibles or jaws project 

 horizontally forwards ; while the fang closes almost longitudinally 

 backwards. 



So far as habits are concerned, it may be added that none of 

 the species spread nets for the capture of prey. Most of them 

 live on the ground beneath .stones, or in deep burrows which they 

 excavate in the soil, and line with a layer of tough silk to prevent 

 the infall of loose particles of earth or sand. At nightfall the 

 spiders may be seen watching at the entrance of their burrows 

 for passing insects, and during the breeding season the females 

 are to be found at its further extremity mounting guard over 

 their egg-cocoon. Other species again live in trees, and spin a 

 silken domicile either between forked branches or in the hollow 

 trunk, or in large leaves rolled up for the purpose. There is no 

 doubt that their food consists almost wholly of insects of 

 various kinds. Nevertheless cases are on record of the de- 

 struction of small reptiles, mammals, and birds by these 

 monstrous spiders. 



The discovery of stridulatory organs in the members of this 

 family dates back to the year 1876, when Prof. Wood-Mason 

 came across one in an Assamese species now known as Musagetes 

 stridulans. Since that year organs like that which he described 

 have been found, not merely in the solitary species as he and 

 most of his successors appear to have thought would be the 

 case, but in a great number of genera ranging from India to 

 Queensland. 



In some of the African Theraphosidcc Mr. Pocock has had the 

 good fortune to discover two stridulating organs, which are not 

 only quite different from each other, but also quite different from 

 those possessed by the genera inhabiting Tropical Asia. One of 

 these organs occurs in the genus Harpactira, the common 

 "Mygale"of Cape Colony. It occupies the same position as 

 the analogous organs existing in the Oriental species, being 

 situated between the mandible and the maxilla. The other, on 

 the contrary, found in Phoncyusa and its allies, is placed between 

 the maxilla and the basal segment of the first leg. 



What is to be said respecting the function of these organs, 

 and what evidence, it may be asked, can be adduced in support 

 of the view that they subserve stridulation ? To this question 

 the answer must be that so far as the African species are con- 

 cerned there is no direct evidence based upon observation of the 

 living animal to show what part they play in the spider's economy. 

 But that their true and probably sole function is the emission of 

 sound, is so strongly supported as to reach practical certainty 

 from what is known of the function of the analogous organ 

 detected by Wood-Mason in the Assamese genus Musagetes. 



Observations have shown that the function of the instrument 

 in spiders of this genus is to emit sound, so it may be concluded 

 that organs constructed upon the same principle, and occupying 

 the same or similar positions, will in all probability be found to 

 perform the same office ; and no further basis need be sought for 

 the belief that the African spiders, Harpactira and Phoneyusa. 

 and their allies, can stridulate as well as their Oriental 

 relations. 



What now is the use to the spider of the sounds that these 

 organs give forth ? It has been suggested that, like the call of 

 the cicada and the chirrup of the cricket, they have a sexual 

 significance, and serve to inform one sex of the whereabouts of 

 the other. This belief, however, has no foundation in fact ; for, 



1 Abridged from an article by Mr. R. I. Pocock in the Zoologist, 

 January 15. 



NO. 1476, VOL. 57] 



in the first place, there is not a particle of evidence that these 

 spiders possess an auditory sense ; and, in the second place, 

 these stridulatory organs are equally well developed in the males 

 and females, and are not, like the sexual stridulating organs 

 known in other groups, confined to the male, or at all events 

 better developed in that sex than in the female. Moreover, 

 they appear in the young at an early age, and beco me functionally 

 perfected long before the attainment of sexual maturity. So the 

 supposition that they act as a sexual signal may be regarded as 

 unsupported by evidence. 



As a matter of fact, the true key to their function is supplied 

 by the behaviour of the living spiders. From observations by 

 Mr. Peal and Mr. E. W. Pickard-Cambridge, it appears that the 

 spiders emit the sound when on their defence and acting under 

 the stimulus of fear or anger, in exactly the same way as the 

 rattlesnake makes use of its rattle. Mr. Pocock points out that 

 the only explanation that has been suggested touching the function 

 of the snake's rattle is that it serves as an advertisement of the 

 whereabouts of the poisonous reptile, so that it may be avoided 

 by enemies which might otherwise inadvertently injure it. 

 Similarly poisonous and noxious insects are decked with warn- 

 ing colours, so that they may be readily recognised and not slain 

 in mistake for harmless or edible species. If this be the true ex- 

 planation of the so-called warning coloration of the insects in 

 question, and of the whirring noise made by the rattlesnake, 

 there .seems to be no reason to doubt that the same significance 

 is to be attached to the stridulation emitted by the peculiar 

 organs recently discovered in the great African spiders. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



Oxford. — The Professor of Mineralogy has been granted the 

 sum of 50/. a year for five years, from January i, to assist 

 in the purchase of specimens and apparatus for his department. 



Sir Archibald Geikie, F.R.S., will deliver the Romanes 

 Lecture at the Sheldonian Theatre on Wednesday, June I. 

 His subject will be "Types of Scenery, and their Influence 

 on Literature." 



The Junior Scientific Club held its first meeting for this term 

 on Wednesday, February 2. Mr. A. W. Brown exhibited 

 and described some life specimens of Aphrodite and two 

 specimens of the unsegmented Cestode, Amphilina. Mr. G. 

 W. S. Farmer read a paper on " Training." Mr. A. E. 

 Boycott (Oriel) is President this term. 



Cambridge. — The Special Board for Biology have re-elected 

 Dr. Arthur Willey to the Balfour Student.ship for one year. 

 The same Board have nominated Mr. K. R. Menon to occupy 

 the University's table at the Naples Zoological Station. 



Mr. W. W. Skeat, District Magistrate of Larut, Perak, has 

 offered to the Ethnological Museum a collection of exceptional 

 interest and scope, illustrative of the fast-disappearing indigenous 

 crafts of Selangor and its neighbourhood. 



Dr. G. Elliot Smith, ad%-anced student of St. John's College, 

 has been approved for the Certificate of Research. His original 

 dissertations relate to the origin of the Corpus Callosum and to 

 cerebral anatomy. 



Mr. H. E. Durham, M.A., M.B., has been appointed one of 

 the representatives of the University at the Madrid Congress of 

 Hygiene, to be held in April next. 



Sir E. Frankland has been appointed an Elector to the chair 

 of Chemistry, Sir W. Turner an Elector to the chair of Anatomy, 

 Prof D. Oliver to the chair of Botany, Sir A. Geikie to the 

 Woodwardian Professorship, Dr. Hugo Miiller to the Jacksoniun 

 Professorship, Mr. L. Fletcher to the chair of Mineralogy, Lord 

 Walsingham to the chair of Zoology, Lord Kelvin to the 

 Cavendish Professorship, Sir W. H. White to the chair of 

 Mechanism, Prof. Schiifer to the chair of Physiology, Lord Lister 

 to the chair of Surgery, and Dr. J. F. Payne to the chair of 

 Pathology. 



In the last paragraph of the Speech from the Throne, read at 

 the opening of the new Session of Parliament, on Tuesday, it 

 was announced that measures for the constitution of a teaching 

 University for London, and for dealing in part with the subject 

 of secondary education, would be brought forward "in case the 

 time at your disposal should permit you to proceed with them." 

 As several other measures are in the same case, the outlook is not 



