104 Bibliographical Notices. 



their influence we read : — " Perhaps the most persistent and 

 destructive natural enemies of spiders are certain Hymcnopterous 

 insects belonging to the large family of wasps . . ," Bearing this 

 in mind, and at the same time remembering that the webs which 

 are exposed for the capture of winged flies must at the same time 

 of necessity be equally exposed to the attacks of the winged and 

 marauding wasps, a close connexion can easily be traced between 

 tlie existence in the Epeirida) of an auditory sense and the enemies 

 that attack them. Of course wasps often prey upon ground-spiders 

 like the Tarantula ; but it does not appear Avhy an auditory sense 

 should be of more use to a Tarantula in this connexion than to 

 B.n Epeira. Is not exactly the opposite the case? The Epcira, 

 owing to the exposed site of his web, must surely be much more 

 liable to the attacks of wasps than is the Tarantula, which spius 

 none. If this bo so, then the power to hear would be of more 

 service to the Epcira than to the Tarantula. Indeed, if the Epeira 

 had no such sense, it seems that the advantage gained by the 

 exposure of her snare for the interception of flies would be counter- 

 balanced by the fact that this very method of obtaining her food 

 ■would, jiari passu, lay her open to the assaults of her enemies. We 

 cannot then accept Dr. McCook's view of the matter until (1) he 

 bases his objection to the one held by Mr. Peckham, which has been 

 here supported, on something more stable than his " contradiction 

 in natural history," and until (2) he shows how an Epeira can 

 discover on which side of her web a vibrating tuning-fork is held, if 

 she is only aware of its proximity through the responsive vibration 

 of her snare. 



In an interesting chapter on the ballooning of spiders the author 

 seeks to account for the distribution of the widespread Ihtcropoda 

 venatoria with reference to this habit. Thus it is found that the 

 geographical belt over which this species is spread corresponds 

 tolerably closely Avith the zone of the trade winds ; and it is sugges- 

 ted that we may look upon these winds, in conjunction with the 

 aeronautic habit, as the agents in the dispersal of the species. The 

 suggestion is certainly interesting and at first seems rea.^onable 

 enough when we recollect that young spiders may be carried to 

 considerable distances through the air when hanging to their silken 

 strands. But it is necessary not to lose sight of the faet that to 

 say tliat the area of the dis^tribution of a species corresi)onds with 

 the area of the trades is only another way of stating that the species 

 in question is a tropical one ; consequently it is clear that the 

 charts on pp. 2G9 and 270, explaining tlie connexion between thtso 

 winds and the known localities for II. venatoria, will apply equally 

 well (o many wide-spread species, which certainly have not the 

 means of travelling which are ascribed to this one. Thus wo cannot 

 accept Pr. ^MeCooks theory until reasons are brought forward to 

 show that the agencies which have effected the distribution of, e. g., 

 Isonntrus maculatus or Scolopendra suhspiiiipes are ineffieient 

 to account for tho similar distribution of IJetiroj>oda viuaioria. 

 "What these agents have been must still be a matter lor debate. 



