40 MISCELLANEOUS PAPERS. 



been noted to travel over the leaf surface with astonishing speed for 

 so minute a creature, but in the majority of cases wliich came under 

 observation it seemed to crawl over the leaf in a slow and cautious 

 manner, turning first to one side of tlie leaf and then to the other, 

 apparently in constant searcli of its host. Unless disturbed it was 

 seldom noted to take flight, but if jarred or frightened it takes wing 

 at once. 



FLIGHT. 



This insect is quite capable of sustained flight, as shown l?y the fact 

 that Mr. Graf captured an adult in the outdoor insectary, on a shelf 

 5 feet above tlie ground and about 15 feet from the foliage wliich 

 held the parasitized thrips. On September 27, 1911, Mr. Graf 

 incorporated in his notes tlie following: 



On this date two adult parasites were noted in flight. In both instances the parasites 

 flew from the desk to the window, a distance of about 24 inches, and probably could 

 have flown a much greater distance. The characteristic rapidity of their short flights 

 in the vials was lacking and they flew slowly and in a zigzag line. Their flight 

 resembled very much that of a fly in its aimless circuit about a room. During the 

 flight they maintained about the same level, so it is probable that these insects are 

 relatively strong fliers. It is probable that in still an* or traveling with an air current 

 they could traverse quite a distance and thus be scattered quite rapidly. This fact 

 is further borne out by the rapidity with which parasitized material of Thrips tabaci 

 was taken from all poiuts of a patch of turnips once it had started to show in one place. 



SIGHT. 



Although this parasite has large eyes, it does not appear to distin- 

 guish objects very plainly or at any great distance. In many cases 

 it was observed, while searching for larvae of its host, to pass near 

 them; so close, in fact, as almost to touch them. In one instance 

 a female, while traveling across a leaf very rapidl}^, was observed to 

 run halfway over a thrips larva, and then, as if just aware of the 

 presence of its host, to stop, back off, and immediately oviposit in it- 

 It is attracted to light and will travel toward it in the vials so that 

 by turning the bottom toward the window, the cotton plugs may be 

 removed without danger of losing the insect. 



BEHAVIOR ON DIFFERENT KINDS OF LEAF SURFACES. 



In the course of the laboratory experunents with the thrips 

 parasite it was observed that it experienced considerable difficulty 

 in moving over the surface of a leaf if the latter w^as hairy or sticky. 

 On leaves with smooth, glaucous surfaces, such as cabbage, turnip, 

 or wild lettuce, this insect moved with rapidity and without ap- 

 parent difficulty. But on the underside of leaves sucli as nasturtium 

 and (liinese gourd, the movements were delayed and often ceased 

 while the insect cleaned its legs. Because of this condition oviposi- 



