23 



on a small area near the river at Central Fortuna is said to have 

 resulted in a noticeable decrease in changa injury. Nymphs or adult 

 changas are not killed even by complete submersion for three hours, 

 and in the field all instars usually will make their way to the sur- 

 face within that space of time. In laboratory tests, changas readily 

 made their way to the surface through 6 inches of flooded soil, and 

 once on the surface of the water they float easily, owing to their 

 air- retaining, pubescent coat. Exposure for even a short time in the 

 field will give insectivorous birds, such as the martinete, ample op- 

 portunity to devour them. Although active swimmers, probably few 

 of the insects will escape the watchful eyes of the water birds. 



In four laboratory tests clusters of changa eggs, either newly laid 

 or almost ready to hatch, failed to survive a submersion of 24 hours. 

 The checks hatched normally. 



Poison baits. Poison baits against the changa are most successful 

 upon small areas, such as garden plats. The cost is an important 

 objection to their use over larger areas, although they have been 

 found practicable by large tobacco planters. Success depends on hav- 

 ing the land so clean of all vegetation that when the bait is applied 

 the changas will be hungry enough to accept it greedily. As the 

 native grasses are among the mole cricket's favorite food plants, 

 clean culture applies to the grasses as well as to crop remnants. 



The most satisfactory bait yet found is a dry mixture of 3 per- 

 cent Paris green with cheap flour. Flour of the poorest quality, even 

 that ruined by weevils and moths, is satisfactory for this purpose, 

 corn meal, cottonseed meal, and bran making good substitutes, though 

 flour seems to be preferred by the changa. Barrett (2, p. 16) re- 

 ported very satisfactory results from the use of a mixture of grass 

 stems, molasses, and Paris green. The Paris green and phosphorus 

 mixture used against crabs is said to be acceptable to changas as well. 



The Paris green and flour bait may be applied in a shallow trench 

 around the young plant at a distance of an inch or more from the 

 main stem, it may be introduced into a changa gallery where it 

 approaches the surface, or it may be spread broadcast over the land. 

 The last method is applicable to especially heavily infested lands. 

 After the area to be treated has been kept clean of vegetation for 

 three or four days, the mixture should be applied, preferably in the 

 late afternoon, at the rate of 300 pounds to the acre. The crop may 

 be planted three to five days after spreading the bait. This treatment 

 on cabbage beds at the Mayaguez station resulted in 50 per cent 

 better stand on the treated plats than on the checks. The broadcast 

 treatment has the added advantage of killing other injurious plant- 

 feeding insects, such as other crickets and cutworms. 



