4 BULLETIN 421^ U. S. DEPARTMENT OF AGEICULTUEE. 



HABITS OF NYMPHS OF THIRD AND FOURTH STAGES. 



The nymphs of the third and fourth stages congregate at some 

 isolated portion of the plant, as along the midribs, at the base, or 

 among the dead or dying leaves (fig. 1), where they remain during 

 transformation. When the attack on the plant has been severe, they 

 will be found more often among the dead leaves. 



The third-stage nymph remains practically motionless unless dis- 

 turbed, when it becomes active and moves rapidly. While at rest it 

 is flattened against the leaf surface. 



Fig. 1.— The sugax-beet thrips (Heliofhrips femoralis): Section of sugar-beet leaf showing fourth-stage 

 nymphs along midribs. Enlarged. (Origiaal.) 



The nymph' of the fourth stage remains motionless and in the same 

 position as in the preceding stage. It is not so active, moving slug- 

 gishly and only for a short distance when disturbed. 



HABITS OF THE ADULT. 



When the adult emerges from the pupa case it is light yeUow and 

 very dehcate, but as it hardens it gradually assumes its character- 

 istic normal dark brown or black. It remains for a short period in 

 the spot where it transformed before seeking food. As in the mature 

 stages, nourishment is obtained by puncturing the leaf cells and with- 

 drawing the plant juices, the adult apparently requiring less food 

 than the nymph. While resting it remains flattened against the leaf 

 surface along the veins and other parts of the plant. It crawls slowly 



