GRAMINEOUS CROPS. 109 



furnished •witli four nearly equal, flat wings, destitute of 

 veins ; but are provided with very long and delicate 

 hairs, which extend all round the wings. All the species 

 of Thri^s are remarkable for the " power of executing 

 leaps of considerable extent in comparison with their 

 size, by the agency of their abdomen, which they bend 

 under them, and suddenly extend." T. cerealium is a 

 small blackish species, not more than one-tenth of an 

 inch in length, which infests the ears of wheat in all 

 stages of growth. According to Vassali-Enandi (an 

 Italian authority), this insect also " attacks the stems of 

 the wheat plants, gnawing them above the knots." It 

 destroys the plants by extracting their juices — thereby 

 causing a lowered vitality, resulting in disease. The 

 male insect is devoid of wings. The metamorphosis is 

 incomplete, the larva being as active as the perfect insect, 

 to which it bears a close resemblance both in structure 

 and habits. In colour both larvse and pupse are yellow, 

 while the perfect insects are black. 



Various species of Thrips attack grasses, clover, 

 potatoes, hops, and other plants .1 



Prevention. — (1) As these insects prefer moist situa- 

 tions to dry ones, it is advisable to thoroughly drain all 

 wheat-growing lands. (2) Miss Ormerod states "that 

 Thrips do most mischief to late-sown wheat, the early- 

 sown crop being too hard at the time the Thrips appear 

 {i.e., in June) for them to injure it." Good cultivation, 

 and the judicious use of manures, are important (although 

 indirect) means of preventing the attacks of this farm 

 pest. Cereal crops generally are greatly benefited by 

 mantiring the land with soluble and insoluble phosphates. 



1 Dr. Eiley's Insect Life, Tol. i. p. 141. 



