96 G. H. CORBETT. 



where the chlorophyll has been removed ; and later, if feeding is continued, the lower 

 surfaces of the leaves acquire a silvery appearance. As the feeding of this insect is- 

 prolonged, the leaves become brownish and tough, owing to the efforts of the plant 

 to repair the injury. In severe infestations the leaves wither up and fall to the 

 ground, preventing the young bolls from developing. 



Leaves frequently present a distorted appearance, curhng inwards, and in the 

 folds the larvae are often abundant. Larvae have been observed neither on the bolls 

 nor in the flowers, but are occasionally seen on the bracts. On plants grown in the 

 laboratory, larvae have been noticed feeding on the stem and root just beneath the 

 surface of the soil. This undoubtedly was due to the leaves drying up and the thrips 

 migrating for food. In no case was the larval stage completed in such situations. 



Though this insect was first observed as attacking fuUy-grown cotton trees, it may 

 be mentioned that the youngest cotton plants are not immune. For egg-laying, 

 preference is shown by the adults for the lower leaves, and then the middle leaves. 

 On young succulent leaves at the upper portion of the plant, the thrips are never so- 

 abundant as they are on the much eaten and tough lower leaves. 



Habits of the Adult. 



The usual mode of progression of the adult is walking, though when disturbed it 

 runs, and frequently takes long quick jumps. Fhght has been observed in a number 

 of cases, but this is not general. Emerging from the pupae in the ground, the adult 

 crawls up the stem to the leaves. In breeding cages it has been noticed to climb up 

 the side of the chimney, and when on a level with the leaves to take a leap to the 

 plant ; this motion is aided by the wings. 



By far the larger number of the adult thrips feed on and lay their eggs in the tissue 

 of the lower surface of the leaf, and confine their attention for the most part to the 

 lower and then the middle leaves of the plant. Flowers seem to be immune from 

 attack, but larvae have been found on the bracts. Very often the adults are found 

 resting and feeding along the veins of the leaves, but, as a rule, no particular part of 

 the leaf is preferred. 



Adults enclosed in vials with plugs of cottonwool die rapidly, but under more 

 natural conditions they have hved for a maximum of fifteen days, though the average 

 works out at five days. The males and females emerge from the pupae about the 

 same time, but there are indications that the pupal stage is shghtly longer in the males, 

 than in the females. 



The female is capable of laying eggs on the second day after emergence. On an 

 average, six eggs each day are laid in the tissue of any part of the leaf, but though eggs- 

 have not been observed, the hatching larvae are more usually found along the veins. 



Habits of the Larva. 



The young larva, on hatching, looks hke a starchy-coloured segmented worm, 

 with red eyes and with no indications of legs or antennae. Gradually it works itself 

 out of the leaf by a shght swaying motion, and standing as it were on its anal 

 segment, unfolds antennae and legs. Later, bringing its legs to the leaf surface, it 

 pulls itself free. 



