176 THE HOUSE FLY— DISEASE CARRIER 



best, and it would also undoubtedly be the best in any 

 event if, by co-operation of the residents or by the 

 active efforts of a central body, like the boards of health 

 in cities, it were possible to do thorough work with the 

 breeding places. 



In cities and in towns, however, where the requisite 

 co-operation cannot be obtained, and where boards of 

 health are still indifferent, careful consideration must 

 be given to the second method, namely, keeping flies 

 out or killing them after they enter. 



A third method has been proposed and is enthusi- 

 astically advocated by Professor Hodge, of Clark Uni- 

 versity, Worcester, which is based upon the supposed 

 time elapsing between the issuance of the adult fly and 

 the period when it lays its first eggs. Professor Hodge, 

 as will be shown later, thinks that it is quite possible 

 to trap these sexually immature adults during this 

 period, which now seems comparatively long, and thus 

 to prevent not only their entrance into houses and shops 

 and markets, but to destroy so many of them that the 

 comparatively few which reach sexual maturity will 

 not be able to lay their eggs in sufficient numbers to 

 make the next generation a nuisance. In other words, 

 he thinks that it will be possible to bring about such a 

 condition that the manure pile may be left undisturbed 

 until it is needed to fertilize the land. 



Whether this can be done or not — and Professor 

 Hodge's argument seems reasonable — will again de- 

 pend upon co-operation in communities, although indi- 

 vidual effort in isolated places may bring it about. 



