104 Bihliographical Notices. 



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

 destructive natural enemies of spiders are certain Hymeuopterous 

 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 

 the existence in the Epeiridce 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 why an auditory sense 

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

 an Ejpeira. Is not exactly the opposite the case? The Epeira, 

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

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

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

 service to the Epeira 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, jirtri jjassu, lay her open to the assaults of her enemies. Wo 

 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 Heteropoda 

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

 geographical belt over which this species is spread corresponds 

 tolerably closely with 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 reasonable 

 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 fact that to 

 say that the area of the distribution of a species corresponds with 

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

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

 charts on pp. 269 and 270, explaining the connexion between these 

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

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

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

 accept Dr. McCook's theory until reasons are brought forward to 

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

 Isovutrus maculatus or Seoloj^endra suhspinijyes are inefficient 

 to account for the similar distribution of Bettropoda venatoria. 

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



