CHAPTER IX. 



THE THYSANOPTERA. 



The very small black flies which are such a source of annoyance 

 to travellers in the summer-time, and which fly into our eyes and 

 crawl over our faces during the prevalence of warm windy weather, 

 principally belong to a kind of insect which is characterised by 

 having very remarkable wings when in the adult condition. These 

 insects exist by myriads, and there are several species of them ; 



The adult insect. 



Tlie lan\i. 



(Magnified.) 



THE INCOMPLETE METAMORPHOSIS OF ThripS cercaliuDl. 



and they are all exceedingly destructive to flowers, and especially 

 to the bloom of cereal plants. The little black insects are to be 

 seen on almost every flower, and they devour the delicate cellular 

 tissue of the petals. TJirips cercaliitm is very destructive when 

 it occurs in multitudes upon the wheat, barley, and oats, for it 

 interferes with the proper nutrition of the grain, by nibbling the 

 protecting envelopes and the tissue which connects it to the 

 stalk. 



All the members of the genus TJirips — and they alone ccn- 



