230 REPORT UPON COTTON INSECTS. 



the first crop or third brood these places, of a few acres in extent, 

 should be thoroughly poisoned. The next brood radiating from these 

 centers may be in great part destroyed by poisoning a slightly greater 

 area 5 and the third crop will thus be greatly diminished, and may itself 

 be 'destroyed by poisoning generally over the plantation, the signal for 

 poisoning being the abundance of eggs, some of which are beginning 

 to hatch. Could such a system be followed by every person raising 

 cotton, I feel certain that it would be very few years before the cotton 

 caterpillar would cease to be the pest that it now is. 



[End of Mr. Trelease's report.] 

 PREVENTIVE MEASURES. 



The most important of the preventive measures which can be adopted 

 is the encouragement of the natural enemies of the cotton-worm. De- 

 tailed accounts of these have been given in a previous chapter; hence, 

 but little remains to be said here. 



The most practicable thing which can be done in this direction is the 

 protection by law of all the native insectivorous birds. An incalculable 

 amount of injury has been done by the indiscriminate destruction of birds 

 by the freedmen since the close of the war. In addition to the protec- 

 tion of the native species, others might be introduced. But here very 

 great care must be exercised, else more harm than good may be accom- 

 plished. No species should be introduced the habits of which are not thor- 

 oughly understood. We wish to call particular attention to this point, as 

 many planters have urged us to aid in the introduction into the cotton 

 States of the English sparrow, a species the importation of which into 

 the Northern States has been pronounced a calamity by nearly all of the 

 American ornithologists. 



The encouragement of the insect enemies of the cotton- worm, though 

 less practicable than the protection of birds, is not less important; for this 

 reason, great care has been taken to figure and describe all the predaceous 

 or parasitic insects which destroy the cotton-worm. It would be worth 

 the while of every planter to become familiar with the appearance of 

 the more common of these, and instruct his hands not to injure them. In 

 those cases in which hand-picking of the pupae of Aletia is employed, 

 much good can be done by taking care not to destroy the parasites con- 

 tained in them. The pupae, when collected, instead of being destroyed 

 should be placed in barrels or boxes covered with coarse wire gauze or 

 other netting. In this way the parasites which emerge from the pupae 

 can be allowed to escape through the raesbes of the netting, and are thus 

 enabled to go on with their destruction of the. pest ; whereas, the moths 

 which mature, being larger, cannot escape, and perish in their prison. 

 Some idea of the importance of this precaution may be gathered from 

 the results of an experiment already cited, in which it was found that of 

 1,721 pupae of the fourth brood, nearly ten per cent, were parasitized. 

 Or what is more to our purpose, there were bred from these pupae 44 

 large parasites (Pimpla, Chalcis, and Tachina), and an immense number of 



