530 THYSANOPTERA CHAP. 



of the plant being pierced only when a supply of food from 

 the usual sources falls short. Members of this family have 

 been reputed as being very injurious to cultivated plants, especially 

 to cereals, and it is said that as a result the harvests in Europe 

 have been seriously diminished. Several species may take part- 

 in the attacks. These appear to be directed chiefly against 

 the inflorescence. Lindeman thought that LimotJirips denticornis 

 ( = Thrips sccalina), and Anthothrips aculeata ( = Phloeothrips 

 frumentarius), were the most destructive species in an attack of 

 Thrips on corn that he investigated in Russia. Uzel suggests 

 that injuries due to other causes are sometimes ascribed to Thrips. 1 

 In hot -houses these Insects are well known, and sometimes 

 occasion considerable damage to foliage. The German horti- 

 culturalists call them black-fly, in distinction from Aphidae or 

 green-fly. Some Thysanoptera live under bark, and even in 

 fungi, and in Australia they form galls on the leaves of trees. 

 This observation is due to Mr Froggatt, and is confirmed by 

 specimens he sent to the writer. Vesicular bodies in the leaves 

 of Acacia saligna were traversed on one side by a longitudinal 

 slit, and on a section being made, nothing but Thrips, in various 

 stages of growth, was found inside them. A second kind of gall, 

 forming masses of considerable size on the twigs of Callistemon, 

 is said by Mr Froggatt to be also due to Thrips, as is a third 

 kind on Bursaria spinosa. It is curious that Thrips' galls have 

 not been observed in other parts of the world. 



Thysanoptera are devoured by small bugs of the genus 

 Triplileps, as well as by beetles ; a small Acarid attacks them by 

 fixing itself to the body of the Thrips. Nematode worms and their 

 eggs were found by Uzel in the body-cavity. He found no less 

 than 200 Nematodes in one Thrips, and noticed that they had 

 entirely destroyed the ovaries. Woodpeckers, according to him, 

 tear off the bark of trees and eat the Thysanoptera that are 

 concealed thereunder, though one would have surmised that 

 these minute Insects are too small to be game for such birds. 

 They have, it appears, no special protection, except that one 

 species (a larva of Phloeothrips sp.) is said to emit a protective 

 fluid. 



Parthenogenesis seems to be frequent amongst Thysanoptera, 



1 See Lindemann, Bull. Soc. Moscou, Ixii. 1886, No. 2, p. 296, and Uzel, Mon. 

 1895, pp. 397, 398. 



