THE GREENHOUSE THRIPS. 49 



turbed, but generally they simply move rapidly. The writer has 

 never observed adults in flight, but that they do fly is certain, as he 

 has found that plants free from thrips and at a distance from infested 

 plants after a time will become infested by adults. As the study of 

 the life history of this species was carried on in an unheated green- 

 house with low temperature, it is quite possible that the adults were 

 rendered sluggish. It seems strange that the writer has not observed 

 their flight, for in studying this thrips he has examined a large num- 

 ber on plants and has purposely disturbed them to induce flight. 

 Adults often remain motionless for long periods, and in such cases rest 

 close to the veins of the leaf. 



The eggs are laid singly in the tissues of the leaf, the female first 

 making an incision with her ovipositor and then pushing the egg into 

 the incision. She probably lays only 1 or 2 eggs in a day, as the eggs 

 are large and the ovaries will hold only a few matured eggs at one time. 

 One female examined had 6 eggs partly formed in her ovaries and 3 of 

 these were quite small. As the leaves become exhausted from the 

 feeding of larva? and adults, the latter leave them and oviposit in 

 fresh young leaves, so that in time the exhausted leaves are deserted 

 and fall off and gradually the remainder of the plant becomes infested. 



HABITS OF THE LARV^J. 



On March 5 larvae were observed hatching from the eggs about 10 

 a. m. In all cases where larvae emerged the leaf was marked by a 

 dark spot and the surface was slightly swollen. 



When first observed the head of the larva was projecting slightly 7 " 

 out of a slit in the leaf epidermis, probably the same one that was 

 made in depositing the egg, and the light red eyes were very conspicu- 

 ous. Little by little the body is w T orked more and more out of the 

 opening, and as it projects in the air, working vigorously back and forth, 

 with its limbs folded against the body and invisible, it has the ap- 

 pearance of a minute worm in motion. When all but the tip of the 

 abdomen is free the tiny larva remains quiet for a very short time, 

 then one by one, beginning with the antennas, but the legs in no regu- 

 lar order, the appendages unfold. The larva moves them around 

 freely for a time and then, bending over, grasps the leaf surface and 

 commences to pull, in an effort to free the end of the abdomen. Aft er 

 considerable work the larva frees itself and after a short rest moves 

 around in search of a place to feed. Some only travel a few inches. 

 others travel over a considerable portion of the Leaf surface before 

 settling down to feed. The time required for the larva to emerge 

 varies from 6 to 12 minutes. 



As a rule the larvae are found on the underside of the leaves, but 

 when crowded, as in severe infestations, they attack the upper surface. 



