THYSANOPTERA OR THRIPS. 



259 



thin, narrow, fringed wings and an imperfect suctorial mouth. 

 The metamorphosis is slight. Several of them are injurious to 

 crops and fruit, and are equally obnoxious in greenhouses. 

 Thripidee are minute dark insects in their adult state, and feed 

 by suction, although the mandibles are represented by a pair of 

 needle-like processes. One species, Thrips cerealium (fig. 149, 

 1 and 2), is often harmful to corn. The larva and pupa are 

 similar in shape to the adult, but are smaller and differ in 

 colour : the larva is deep yellow, with two dusky spots on the 

 thorax ; the pupa is pale yellow, with white legs, antenlise, and 



Fio. 149.— Thrips. 



1, Female Tlirips cerealium with wings closed ; 4, with wings 

 nat. size ; 6, larva of T, mimttissima ; 8, T. minutissima. (Curtis.) 



; 2, 3, 6, Y, 



wing-cases. The eyes and ocelli are reddish. The adult is deep 

 black and winged in the female, apterous in the male. The 

 legs are paler, and the two-jointed tarsi terminate in a little 

 gland, hence they are sometimes called " Bladder-feet.'' The 

 Corn Thrips is about f of a line long. This pest feeds off the 

 haulm, between the sheathing leaves, and off the developing 

 grain, and is especially noticeable in the furrow of the wheat 

 seed. They cause the grain to shrivel up, and often produce a 

 white sickly appearance, similar to a disease caused by them in 

 grass in Canada. Another species, T. ochraeeus, is frequently 

 most harmful to melons, cucumbers, tomatoes, &c., under glass. 



