THE BOLL WORM REMEDIES. 377 



Under this head of predaceous enemies we may properly mention He- 

 liothis itself, but we have already given particulars of its cannabalistic 

 habits. 



It was thought for a long time that the Boll Worm was absolutely 

 free from true parasites, but this has been proved untrue. Three spe- 

 cies of parasites have been bred and undoubtedly more will be found. 

 In 1872 we bred Tachina anonyma Riley from Heliothis armigera^ and 

 mentioned the fact- in a foot-note to page 129 of our Fourth Missouri 

 Entomological Report. In 1879 the species of Tachina which we have 

 described as Tachina aletiw {Canadian Entomologist^ XI, p. 162), and 

 which is also, as the name implies, an important parasite of Aletia, was 

 bred at the Department from a Boll Worm collected at Selma, Ala., by 

 Mr. Trelease. The white eggs of this Tachina have also been observed 

 by Mr. Hubbard at Crescent City, Fla., by Judge Johnson at Holly 

 Springs, Miss., and by Prof. R. W. Jones at Oxford, Miss. The latter 

 says : 



In the latter part of tlie season a great many larvae of Heliothis and Aletia bore a 

 white egg which was found to be Tachina. In some instances the moths hatched out 

 notwithstanding the eggs of the parasite. In other cases the chrysalis was destroyed 

 by the grub ; the latter was generally the case. Sometimes as many as five eggs of 

 Tachina would be found on one larva of Heliothis or Aletia ; more generally on Ale- 

 tia than Heliothis. This Tachina must be an exceedingly formidable enemy of both 

 Aletia and Heliothis. 



It is interesting to note that Tachina eggs were observed on Boll 

 Worms many years ago. Mr. J. W. Boddie, writing in 1850, says (see 

 Bibliographical List): "I cannot account for their disappearance, for 

 the season was favorable. They may have been destroyed by some of 

 the Ichneumonidae family, perhaps the white ohlong dots we saw on them. 

 I never saw them on the first brood or their eggs.'' 



The remaining parasite is also one which is common to Aletia. It is 

 the Trichogramma egg-parasite, Trichogramma pretiosa Riley (see page 

 102). It was bred by Mr. Hubbard from the eggs of Heliothis at Cres- 

 cent City, Fla., and the specimens sent were accompanied by the note: 

 "Eggs of both Aletia and Heliothis parasitized turn black on or by the 

 second day j the Chalcids disclose about 7 or 7 J days from the time the 

 eggs are stung." The only point in which the parasitism of the eggs 

 of the Heliothis will be found to differ from that of Aletia eggs is that, 

 owing to its greater capacity, the egg of Heliothis will probably sus- 

 tain more of the parasites. 



REMEDIES. 



Under the head of remedies we may briefly mention in the first place 

 two plans which have had strong advocates for many years. These are 

 topping the cotton and rotation of crops. The first of these plans has 

 been followed by many planters, but it is an easy matter to show, as has 

 been done with Aletia, that the number of eggs laid upon the part of 



