198 A. D. PEACOCK — ENTOMOLOGICAL PESTS 



Farias biplaga, Walk. (Plate XXIV, fig. 5). 



The eggs are unknown. The larva is ; spiked ' in appearance and pleasingly 

 coloured, being blotched with green and yellow with touches of red. It grows 

 to about | inch in length and then spins a cocoon of white silk about J inch in 

 length, and shaped like an overturned boat. These may be found on bracts of 

 the bolls and even on weeds in the cotton field. The pupal stage lasts from 1 1 to 

 15 days. 



Chloridea obsoleta, F. (Plate XXIV, fig. 10). 



The eggs have not been observed. The larvae noted were of a green colour 

 and reached a length of about 1J inches, being much larger than those of either 

 of the other two species. The pupal period occupies 14 days, the larva pupating 

 in the soil. 



The indigenous food-plants of these pests have not been ascertained, nor is 

 there any information as to the number of generations in a year. But the serious 

 condition of a great number of plants observed in 1911 must mean either a large 

 first generation or the quick succession of more than one generation. 



No natural enemies have been discovered so far in the Colony, but it is prob- 

 able that there are such. 



Diparopsis castanea and Farias biplaga were detected during the cotton season 

 of 1911, the former being the principal boll pest. Chloridea obsoleta was not 

 observed till the 1912 season, but the caterpillars were then very plentiful, 

 though their relative importance as compared with D. castanea is not known. 



Indigenous cotton also suffers from the attacks of these insects, but it is diffi- 

 cult to compare the damage with that done to the American varieties, for the 

 size of the native plants makes investigation almost impracticable. But the 

 condition of the plants towards the end of the 1911 season was found to be 

 serious. 



Treatment. 



Imported Cottons. — Experience has shown that the time taken to examine, 

 detect and hand-pick the affected bolls was very long ; and dusting the bolls with 

 dry poisons would also be too lengthy a process for practical purposes. Of 

 course young children might be taught to do the work quickly and skilfully, but 

 the advantages of spraying are greater, and this method is effective against 

 the leaf-rolling caterpillars as well as the boll-worms. 



The method of attack may be outlined as follows : — 



(1) A careful look-out should be kept for leaf-rollers and boll-worms during 



August and September. 



(2) Immediately the presence of the insects is detected, the leaves, bracts, 



bolls and buds in the affected area should be most thoroughly sprayed. 



(3) The number of sprayings must depend upon the condition of the crops 



as the season advances. 



(4) At the end of the season all the old stalks with the diseased bolls should 



be burnt. 



