224 SCIENCE PROGRESS 



hopper, while only a single egg goes to the nutriment of each 

 myrmarid (Paranagrus and Anagrus). 



When the last report was received the advantage was 

 nevertheless held to lie with one of the two species of Parana- 

 grus. which is alone capable of destroying about 50 per cent, 

 of the hopper's eggs. The Ootetrastichus, on the other hand, 

 was slowly but surely making headway, so that in course of 

 time it will probably become the most efficient instrument of 

 destruction, although not before the year 1908. 



The imported egg-parasites are largely assisted by various 

 native insects which feed on the leaf-hopper, together with a 

 fungus which attacks the latter. Had it not been for these 

 native agencies, it is well-nigh certain that sugar-planting would 

 have ceased to be a Hawaiian industry. As it is, the loss is 

 already estimated at millions of dollars. 



If it be asked whether the combined attacks of the parasites, 

 the predaceous insects, and the fungus are now sufficient to 

 prevent serious damage from the leaf-hopper, the reply is that 

 more time must be allowed before a definite answer can be 

 given. A strong hope is, however, expressed in the Bulletin 

 that the combined array of forces will eventually prove sufficient 

 to keep the enemy under control. 



Reverting to the Central Bureau at Washington, our final 

 illustration may be directed to emphasising the fact that the 

 destruction of noxious insects is by no means its sole aim and 

 object. On the contrary, efforts are made to put such industries 

 as silkworm-rearing and bee-keeping on a more efficient and 

 scientific basis. An example of work of this nature is afforded 

 by the Bulletin on the rearing of queen bees issued by the 

 Bureau in 1905. 



It is held by the best bee-keepers to be essential (if the most 

 is to be made out of the industry) to re-stock all hives annually 

 with new queens ; but to a great extent the practice is neglected 

 — at all events, in America. This is due in a large degree to 

 the difficulty and expense usually connected with obtaining a 

 sufficient stock of new queens. The Bureau has, however, 

 succeeded in finding a method whereby they can be raised in 

 any numbers at a comparatively trifling cost, and with very 

 little trouble ; and it is therefore hoped that in the near future 

 the practice of raising a sufficiency of queens to re-stock all their 

 hives will become universal among bee-keepers. 



