CLASSIFICATION AND DESCRIPTION OF COMMON INSECTS 121 



Adult. — One-fifteenth inch long; head and thorax dark brown, 

 abdomen yellowish brown; antennas with 8 segments; 3 to 4 weeks for a 

 generation; fore- wings with two, hind- wings with one longitudinal vein. 



E^gs. — Hatch in 5 to 8 days; laid singly in leaf tissue; colorless and 

 bean-shaped. 



Nymphs. — Mature in 20 to 25 days. 



Onion Thrips or "White Blast" (Thrips tabaci Lind.). — Attacks a 

 large variety of garden plants. Found on bulbs of onion in loose soil 

 and at axils of leaves. Punctures the tissues and sucks the sap, giving 

 the field a whitish appearance. Produces also scuUions or thick 

 necks. 



Fig. 76. — Wheat thrips (Euthrips Iritici) . Greatly enlarged. (After Folsom.) 



Adult. — One-twenty-fifth inch long, active, slender, yellowish tinged 

 with black, two pairs of bristly narrow wings which fold along the back. 

 Probably winters over in the rubbish on the ground; life-cycle about 

 3 weeks, hence several generations in a season. 



Eggs. — ^Laid singly in spring or early summer within the leaf tissue, 

 3^foo i^ch long, elongate and curved; hatch in about 4 days. 



Nymphs. — Transparent at first, later greenish-yellow; mature in 

 II or 12 days. 



Control. — Spray with solution of nicotine sulphate and whale oil 

 soap (4 oz., 4 lb., 40 gal.) 



