272 TOBACCO 



on the voyage to the Dutch East Indies. There the 

 various kinds were multiplied as fast as possible. The 

 most important of these is Trichogramma pretiosa, which 

 it is now possible to increase artificially almost in a whole- 

 sale manner; this little wasp parasitizes the eggs of a 

 large number of insects, chiefly tliOiSe of Heliothis, 

 Prodenia, and Plusia. Hundreds of thousands of speci- 

 mens of it are liberated annually in the tobacco planta- 

 tions when it appears that there are many Heliothis 

 eggs present. It has already been proved that this little 

 wasp can maintain itself in a wild state for more than 

 half a year, and there is therefore every reason to assume 

 that it is either already a member of the fauna or will 

 soon become one. 



The propagation in the laboratory of a few other kinds 

 of wasp which parasitizes the eggs or the caterpillars has 

 not been successful, so that only a very small number 

 of them could be liberated. 



Certain Coccinellides (e.g-, Megilla, Hippodamia, 

 Chilocoms, and Coccmella) which devour green-fly have 

 been imported from America and Europe, but only in 

 the case of Megilla maculata has it been found practicable 

 to breed them on a large scale. From its very nature 

 this beetle cannot, however, be produced in such large 

 numbers in a short time as the small Trichogramma. 

 Several thousands of the Megillas have been liberated 

 annually at apparently suitable spots, but so far no 

 specimens of succeeding generations which have 

 developed entirely in a wild state have been found. 



As maize is a very favourite plant of the female 

 Heliothis on which to deposit her eggs, experiments have 

 been made on a large scale with a view to utilizing this 

 plant as a trap plant. The results vairied greatly in 

 different localities. 



It was found that Prodenia is very fond of depositing 

 its egg-nests on the large leaves of the very common 

 Limno charts flava, which came here from South America 

 via Java; it appeared to be of importance to have 

 this plant, which grows in ditches, regularly examined 

 for Prodenia nests, not only when the tobacco is growing, 

 font at other times also. 



