140 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



the stem, usually causing a slight enlargement. When the 

 worm is full grown it will be found in the crown of the plant, 

 having eaten out and totally destroyed the embryonic head, 

 its body occupying the cavity thus formed. 



"The females which deposit these eggs, being small and fre- 

 quently wingless, are in no way fitted for traveling long dis- 

 tances. The larva or worm is of a very light stra\v color, indeed 

 almost white, with brown jaws. These worms develop very 



rapidly and, as they feed 

 on the most nutritious part 

 of the plant, they become 

 robust and larger than 

 those found in the mature 

 straw in late summer. In 

 May the larva? become full 

 grown and pass at once 

 through a short pupal 

 stage. The pupic are at 

 first the same color as the 

 larvae, but later change -to 

 a shining jet black. In 

 a few days the fully devel- 

 oped insects gnaw circular 

 holes through the walls of 

 the stem and make their 

 way out. These adults are 



much larger and more robust than the individuals of the first 

 generation and are provided with fully developed, serviceable wings. 

 That they make good use of their wings, and scatter themselves 

 about over fields adjacent to their place of development, is shown 

 by their occurrence in fields of grasses (in the stems of which 

 they do not breed) situated considerable distances from wheat 

 fields. In ovipositing, the females of this generation select 

 the largest and most vigorous-growing stems in which to place 

 their eggs. 



" The adults of the second generation deposit their eggs 



6 



FIG. 102. The wheat straw-worm: 

 method of oviposition of female of 

 summer form: , female inserting 

 her eggs, b, section of wheat stem, 

 showing egg; c, and ovipositor, d; 

 c, egg, greatly magnified. (After 

 Riley and Webster, U. S. Dept. Agr.) 



