318 INSECTS AND MAN 



why, when once established in Florida, these two minute 

 insects should not work miracles among the orange groves. 



America has done its share of exporting, as well as im- 

 porting, enemies of injurious insects. For a number of 

 years the larva of a moth known as Chloridea obsoleta has 

 been an inveterate enemy of various crops, among them 

 being cotton, maize, tomato, and tobacco. This moth, 

 which is practically cosmopolitan, also occurs in Sumatra, 

 where it does immense damage to rice, maize, tobacco, and 

 cotton. In the United States the pest has been kept 

 under control by a hymenopterous parasite, Trichogramma 

 pretiosa, and the experiment was tried of shipping a 

 number of parasitised Chloridea eggs to Sumatra in cold 

 storage, in the hopes that the resultant insects would 

 lessen the pest. As with almost all similar experiments, 

 the early efforts were doomed to failure the parasitised 

 lepidopterous eggs could not be transported in good condi- 

 tion over the long journey from America to Sumatra. Not 

 to be thwarted, an intermediate station was instituted at 

 Amsterdam in Holland; parasitised material was safely 

 transferred there from America, carefully tended in its 

 new home^ and a fresh generation was transhipped to the 

 South Seas. This second effort proved more successful 

 than the previous one, in that all the parasites arrived 

 alive, but when they emerged from their hosts they were 

 found to be all males. Further efforts showed that the 

 trouble that had been expended was not in vain, a large 

 percentage of parasites hatched out in their new home, and 

 there was such a proportion of males and females as to 

 ensure a continuance of the race. 



As in America, so in the land of its adoption, Tricho- 

 gramma proved catholic in its tastes and was observed to 

 parasitise over twelve species of lepidoptera. The import- 

 ance of this will be easily realised when we consider that 

 in a new country the supply of one insect may fail for a 

 season, owing to climatic or other causes. If the imported 



