W. COLE ON A PARASITE OF HUMBLE BEES. 103 



favourable conditions. The astonishing fecundity of many Entozoa 

 is well known, but probably few animals more faithfully fulfil the 

 command, u Increase and multiply," than Splice rularice. The young 

 absolutely swarmed in all the infected bees I examined, and on 

 making the necessary incisions in the abdomen, they flowed out in 

 myriads, rendering the surrounding water quite milky. A few 

 drops of this fluid placed in a watch-glass, and examined under a 

 low power, presented a very curious spectacle, the whole collection 

 of worms being in a state of rapid motion. As the result of some 

 experiments, Sir John Lubbock estimated that one bee contained 

 50,000, one 60,000, and a third over 100,000 young Sphcerularup, 

 and my own observations fully confirm this statement. Even these 

 figures, however, do not represent, by any means, the numbers that 

 may possibly be developed in a single insect. At the time the 

 young are found so numerously, the ovaries of the worms are filled 

 with germs in every stage of gi-owth, and I have frequently found 

 a dozen or more full-grown Sphcerularice in one bee, each busily 

 engaged in adding egg after egg to swell the ranks of the already 

 teeming multitudes ! 



It is plain that, whatever be the economy of the parasite, the 

 destruction of the young must bear a direct proportion to the pro- 

 lilicness of the species, otherwise the prodigious increase of the 

 parasite would exterminate the humble-bees in a couple of seasons. 

 As Sir John Lubbock observes, " It is evident that, if the sexes 

 of a given species are equal in number, and if the species is neither 

 increasing nor diminishing, the chances against any given young 

 one attaining to maturity may be obtained by halving the average 

 number of young ones produced by each female." Applying this 

 principle to the species before us, we may calculate the chances to 

 be about 5,000 to one against a young Sphcemlaria finding a per- 

 manent home in the body of a bee. 



Presuming the foregoing view as to their life-history to be correct, 

 a slight consideration of the known habits of humble-bees will enable 

 us to account for the fact I have before stated, namely, that Sphoeru- 

 larice are only found in the large females. We cannot imagine that 

 the young parasites would be capable of exercising any power of 

 selection as regards the sex of their victims ; they would probably 

 crawl on to males, workers, and females quite indiscriminately. In 

 the two former events, however, their existence would be speedily 

 nipped in the bud. The female Bombi are the only individuals 



