192 THYSANOPTERA AND ORTHOPTERA. 



supposes enables the insects to go through small jDassages. The same 

 author states, however, that this tooth is sometimes larger in the male 

 than in the female, an observation confirmed by Hood (1908 a, p. 371) 

 for Neothrips corticis and by my own work. Furthermore, the tooth 

 is sometimes present in the male and wanting in the female. It seems 

 to me more probable, since the tooth is located on the inner side and 

 hence is not in a position to be thrust into plant tissues, that it serves 

 rather to enable the male to hold on to the back of the female. I am 

 led to this belief the more strongly, notwithstanding the fact that the 

 females of some species also possess these teeth, because the tarsi of 

 the majority of the members of the suborder Terebrantia are unarmed; 

 and I believe it will be found on further observation that in most of the 

 species of this suborder the males are not carried by the females dming 

 copulation. However, the Aeolothripidae have armed tarsi and it will 

 be interesting to learn how they copulate. 



Mode of Reproduction. It is not known of any one of the species 

 taken, so far as I can learn, what the ^lethod of reproduction is through- 

 out the season under natural conditions. At least one species (Anapho- 

 thrips striatus) has been bred parthenogenetically in the laboratory 

 (Hinds, 1902, p. 163). The male exists, however, for out of some two 

 hundred specimens collected at fourteen different times and places at 

 intervals from June 15 to August 20, two individuals were males. Both 

 of these were taken from sea sand-reed (Ammophila arenaria) on July 

 7. The male of this species has not, so far as I know, been known 

 hitherto. It seems very doubtful if these rare males ever fertilize any 

 eggs. Other species w^hose males are unknown or rare are presumably 

 either exclusively or occasionally parthenogenetic. I have found no 

 evidence in any species that the males are common only at certain 

 times of the year. 



Those species whose copulation has been observed (Eutkrips tritici 

 and Anthothrips verhasci in my own work) are of course presumably 

 bisexual; and the fact that males are common in both these species 

 throughout the active season suggests that they may be exclusively 

 bisexual. Yet, it may easity be that females of any of these species, in 

 the absence of males, reproduce parthenogenetically. There is need 

 of further study of eA'ery species to determine this matter of partheno- 

 genesis. 



Dissemination. 



Local distribution. A species which can and does readily change its 

 location, especially over considerable distance at one time, should be 

 nearly equally distributed over its habitat wherever external conditions 

 are the same. Such a species, unless it were a social one, if unusually 



