208 INSECTS AFFECTING VEGETATION 



once, cutting it low and clean, and in so doing starve a large ma- 

 jority of this generation of worms, thereby protecting the next crop 

 as well as saving a part of the one already affected. Get the ranch 

 in the best possible cultural condition. Irrigate often and thor- 

 oughly and as soon after cutting as the crop of hay can be gotten 

 off the ground. Cut close to the ground and clean, especially along 

 the ditch banks, borders, and turnrows, as well as in the main part 

 of the field. Cut the crop early. When just coming in bloom is the 

 proper time. Watch for caterpillars in the early spring crop, and 

 if many are observed about grown cut the hay a few days before it 

 is in bloom, and thus save the next crop. Pasture alfalfa whenever 

 possible, as a minimum amount of damage occurs in such fields. 



Use the methods just mentioned on early spring crops, no mat- 

 ter whether any worms are noticeable or not, and thus avoid any 

 risk of having overlooked them. The satisfactory results must come 

 from an application to an early crop. Renovate every winter, either 

 by disking or by the use of an alfalfa renovator, thus disturbing any 

 pupae that may be wintering over, and putting the land and alfalfa 

 in condition for good growth the following spring. 



These methods, while they will probably be of value in other 

 sections, have been tried only in the Imperial Valley of California, 

 and they are not specifically recommended for sections where cli- 

 matic and other conditions differ from those found in this valley. 

 (Cir. 133, U. S. D. A. B. E.) 



The Grass Thrips. The adults pass the winter at the bases of 

 the grass stems just above the ground. In the spring as soon as the 

 weather is sufficiently warm to start the grass, they become active and 

 begin to deposit eggs, continuing to do this for from four to six 

 weeks. The eggs are deposited in the tissues of the fresh and ten- 

 der parts of the leaf, and one female may lay quite a number, in- 

 dividuals kept in confinement averaging from fifty to sixty each. 

 The length of time between egg-laying and hatching appears to vary 

 somewhat according to the weather. Eggs laid in early, spring 

 hatch in from ten to fifteen days, but during the summer much less 

 time is required. When the egg hatches the young thrip works its 

 way up out of the leaf till it is nearly free, where it remains until its 

 body has sufficiently dried, when it pulls itself entirely out and soon 

 begins feeding. When full grow r n it is about four times as long as 

 when it left the egg. 



The full grown larvae or young, now seek for some protected 

 place in which to pass through the next stage of life the pupa. 

 Sometimes the place selected is between the stem of the grass and 

 an upper leaf sheath, but usually it is in similar places at the base 

 of the stem near the ground. Here they move about but little, doing 

 no feeding. In this condition they remain for a few days, at the 

 end of which time, the outer covering is thrown off and the adult 

 insect appears. 



The adult insects are of two kinds, viz., those with wings and 

 those without. Over 90 per cent of those of this first spring gen- 

 eration are winged, and are thus able to fly and infest new fields. 



