124 



them only two or three. It proved impossible to rear the parasites 

 from most of these larvse, for the latter were nearl}^ all affected with 

 a bacterial disease and died before the parasites could attain full 

 growth. 



The records are very meager, but serve to show that Tachinidse are 

 of but little assistance in controlling the bollworm. 



During the past season the life history of one parasite, Winthemia 

 Jf-jnistulata Fab. (see fig. 26), w^as worked out. A female kept in the 

 laborator}^ deposited eggs on three different boUworms, laying five or 

 one, seventeen on another, and one on a third. The eggs are 0.8 mm. 

 in length, elongate-oval in shape, and pearly white at first, but afte 



twenty-four hours they tur 

 to an orange-yellow color. 

 The duration of the life cj^cle 

 is as follows: Egg, two days; 

 larva, three days; pupa, nine 

 to ten days. 



Summarizing the conclu- 

 sions to be reached from a 

 study of the insect parasites 

 of the bollworm, it is evident 

 that the destructiveness of the 

 third and fourth generations 

 is materiall}^ lessened by them. 

 During September, 1904, when 

 the fourth generation should 

 have been damaging much of 

 the late cotton in northern Texas, it was almost impossible to find an}^ 

 bollworms on cotton, and the few to be obtained in the neighboring- 

 alfalfa fields were invariably attacked b}^ parasites. At the same time 

 adult specimens of Microplitis could almost alwaj^s be collected in these 

 locations by the use of the sweep net. Meanwhile, the late corn nearby, 

 where the parasites could not get at the larv», was badl}^ damaged. 



Such evidence plainl}^ suggests that the dearth of larvae on cotton 

 at this time must have been, in a measure at least, due to the good 

 work of parasites. 



DISEASES. 



Fig. 26. — Winthemia k-pustulata: adult and parasitized 

 moth pupa (original). 



BACTERIAL DISEASE. 



There is only one disease that plays an important part in the econ- 

 omy of the bellworm. It is one evidently caused by bacteria, although 

 its exact nature has not been clearly worked out. Its effects are most 

 clearly apparent among larvae feeding on corn, more especially those 

 of rather large size. 



