4 PRESIDENT'S ADDRESS. 



very great, and if a good proportion reached maturity, the 

 world would be overwhelmed by them, but fortunately they 

 have many enemies, and the numbers keep fairly constant. 

 Given however, propitious circumstances, this fact will easily 

 account for the swarms which occasionally appear, and for an 

 insect which is rare one year being common the next. The 

 same observer noted that the tenants of a rather small nest 

 of the common wasp, Vespa germanica, brought home about 

 2,000 flies in a day. In speaking of wasps, I should like to 

 allude to the most interesting and, I believe, hitherto unnoticed 

 colour sense in a solitary wasp (Odynerus parietinus, L.) 

 which was observed by Major Platt of Dorchester, and 

 which is the subject of a paper by myself contained 

 in our last volume of Proceedings. The wasp showed its 

 preference for light blue (a colour to which honey bees 

 are partial) by choosing three reels of this colour in which 

 to make its nests, out of about 32 reels of variously coloured 

 cottons. For further particulars I must refer you to the paper 

 in Vol. XLI of our Proceedings. From investigations carried 

 on in the Parasitical Laboratory at Aberdeen, it would appear 

 that the Isle of Wight Bee disease is caused by a small mite 

 (Tarsenemus) which inhabits the respiratory system of the bee, 

 where it breeds and finally stifles the bee by cutting off the 

 air supply by its numbers. The disease had been believed to 

 be due to a Protozoon. I referred just now to our ignorance 

 of an early stage in the growth of the lobster. Until recent 

 years the method in which fresh water eels were propagated 

 was a complete mystery and there was some excuse for the 

 ancient idea, probably still much believed, that they were 

 developed from horsehairs. It is now known that eels live for 

 years in fresh water, and when at length they attain maturity, 

 they migrate to the depths of the sea and there spawn, though 

 so far, no one has seen a spawning eel. The young ones, about 

 a third of an inch long, in what is called the Leptocephalm 

 stage, have however been met with at a depth of 2,000 fathoms. 

 Our ignorance of even the best known fishes was much insisted 

 on by the President of the Zoological section of the British 



