1916] Williams — Neio Species of Tkripoctenus 57 



After the parasite's relation to the Thysanoptera had been 

 established the locality where the galls had been collected was 

 re-visited, and large numbers of additional specimens secured from 

 time to time. These galls were not, of course, the work of the 

 thrips. They were practically all on dead wood, and may have 

 been several seasons old. The commonest type, and that most 

 frequented by the thrips was the one shown in Fig. 1,1, but the 

 insects were also found in other sorts, among them the well- 

 known "pine-cone" willow gall. The original inhabitant of the 

 gall is therefore of little importance, since the thrips evidently 

 occupy any sort that will accommodate them. 



The galls are not a mere temporary shelter, as all stages of the 

 thrips from the egg to the adult were to be found in them, and none 

 were found outside, upon the twigs. There seem to be no definite 

 generations, all stages being obtainable at any time during the 

 period for which they were under observation. What they eat, 

 unless they are able to subsist on the dry wood of the gall, seems 

 a mystery, the dead willows being the only visible source of nour- 

 ishment. The other insects found in the galls are scarcely suffi- 

 cient to permit of a regular carnivorous habit, although occasional 

 cannibalism is not unlikely. 



Habits oj the Parasite. 



The life-history of Thripoctenvs russelli has been studied in 

 detail by Mr. H. M. Russell of the Entomological Bureau. The 

 writer has not been able to treat the present species so exhaustively 

 within the time at his disposal, but the details gathered show many 

 points of similarity between the two species as well as several in- 

 teresting differences. 



Oviposition : On the 16th of August no parasites had issued 

 from the new lot of galls, and to hasten matters a number were 

 cut open, several female parasites rewarding the search. Two or 

 three of these were placed in a vial with an immature thrips. 

 At first they ran around without paying any particular attention 

 to it, but before very long one of them ran up, examined the thrips 

 briefly with its antennae, and then immediately thrust its abdomen 

 forward between its legs and punctured the larva with its oviposi- 

 tor. After a moment, however, it relinquished its attempt for no 

 apparent reason. Later the same thrips was approached by a par- 



