190 THYSANOPTERA AND ORTHOPTERA. 



wing fringes when flight occurred, thus hardly giving them time to get 

 a secure footing. 



After few or many of these movements had been made, the insect 

 would fly, and there was apparently no way of determining when it was 

 ready to do so. Sometimes the abdomen was raised but once; in other 

 cases I have found the entire preparation for flight to occupy over 20 

 seconds. The abdomen was sometimes lowered after combing the 

 "^ings and before flight began, l)ut flight was often commenced while 

 the abdomen was still elevated. 



The flight is irregular and dancing, often not unlike that of a A-ery 

 small midge in a swarm. The rapidity of flight varied consideral^ly in 

 different species and in different individuals of the same species. One 

 specimen of Euthrips tritici flew about 30 cm., another 45 cm., in one 

 second. The only specimen of Ctenothrips hridweUi which was timed 

 flew about 90 cm. per second. 



Leaping. The more active species, like Thrips tabaci and Euthrips 

 tritici, frequently leaped for short distances. Hinds (1902, p. 112) has 

 descrite.d leaping as Ijeing effected by elevating the abdomen and l^ring- 

 ing it down forcibly upon the surface on which the insect rests. After 

 many careful observations I am convinced that the movement of the 

 abdomen is not the cause of the leap, for the abdomen was sometimes 

 plainly still elevated when the leap occurred, and at other times the 

 abdomen was lowered l^efore the leap occurred, the two acts being 

 separated iDy an observable interval. Furthermore, if the insect was 

 suddenly disturbed, it sometimes leaped without raising the abdomen. 

 Often the leap was preceded by all the movements of combing the 

 wings with both abdomen and legs; in such cases the leap might well 

 have been only an unsuccessful flight. Specimens of Euthrips fuscus 

 taken elsewhere in September usually raised the abdomen when about 

 to leap. As this is a wingless species, it is not certain what function, 

 if any, may here be served by raising the abdomen; it may ])e merely 

 to throw the center of mass farther forward over the middle legs, and 

 so prevent the anterior end of the body from being unduly raised by 

 the act of springing, or it may be functionless. 



Leaping is insignificant from the standpoint of dissemination, for a 

 leap assisted by the wings was usually found to be only 10 to 20 mm., 

 rarely more than 25 mm., while a leap without the assistance of the 

 ■wdngs varied from 3 to 10 mm. As a means of escaping from sudden 

 danger, however, springing is probably quite effective. 



Reproduction. 



Copulatioyi. I have observed this many times in Anthothrips ver- 

 hasci, representing the Tubulifera, and several times in Euthrips tritici 



