136 PROCEEDINGS OF THE 



These examples will illustrate the general rule, and make the 

 case of the striking exception in the sand martin more patent. 



I do not pretend to be able to account for this curious 

 departure from the rule, but again merely suggest, that possibly 

 food may have something to do with it. Nor can I say what this 

 food actually is, but I cannot divest myself of the idea that the 

 poisonous and innumerable mosquitoes form a large part of their- 

 food supply. Unfortunately our friend Piothich did not examine 

 the contents of this bird's stomach, and so put this question of its 

 food beyond doubt; but what are all these pests created for if it 

 is not to supply food for the legions of birds that haunt the 

 tundras and river banks in summer 1 Is it not possible that if the 

 sand martins feed mainly upon mosquitoes^— I wont say entirely— 

 that the effects of the quantity of the poison which they swallow 

 may affect their colour 1 In other words, is it not possible that 

 there is a property in the said poison capable of affecting the 

 blood without injury to the bird, and yet, through the blood, 

 causing this marked variety of plumage"? 



Professor Thomson of London once asked me to catch and 

 bottle as many Persian bugs as I could (at that time I con 

 templated a visit to Persia), these bugs being so venomous that 

 their bites are sometimes almost fatal. He wished to express the 

 poison afterwards, and discover its properties and composition, if 

 possible. If mosquito poison could be treated in a similar way, 

 possibly it might be proved to contain some property which 

 might have the effects I suggested, and if it could be analyzed, 

 no doubt an antidote to the poison might also be discovered, 

 which to poor humanity exposed to its tortures would be an 

 unspeakable relief. But there is no need to go further into what 

 after all is mere hypothesis, and what may just as likely as not 

 prove to be altogether wrong. Still I think the subject is worthy 

 of some attention from this point of view. 



III. — 071 the Biscacha ( Larjostoiims trichodadijhis, Brookes), a South 

 American Rodent. By Mr Ernest Gibson, Buenos Ayres. 

 Communicated by Mr IIarvie-Brown, F.Z.S. 



The biscacha cannot be regarded merely as an interesting 

 subject for observation by the naturalist, or as affording some 

 moonlight sport for gun and revolver; for, in the province of 

 Buenos Ayres, it ranks with the thistle and the " Tuco-tuco " 



