INSECTS INJURIOUS TO SMALL GRAINS 



141 



begins in spring is effectively held in check by its natural ene- 

 mies, and notably by a minute, black wasp-like insect, Lysiphlebus 

 testaceipes Cress. (Fig. 

 120), that deposits 

 eggs singly in the 

 'green bugs, ' the 

 grubs hatching from 

 the eggs feeding in- 

 ternally on the bug 

 and destroying i t 



(Figs. 122-123). Other w 



, FIG. 121. Lysiphlebus parasite in act of depositing 



natural enemies are eKKS j n the body of a grain-aphis much enlarged, 

 the larvae of certain ( After Webster, U. S. Dept. Agr.) 



predaceous flies, and the larvse and adults of lady-beetles. The 



little wasp-like parasite first mentioned, 

 however, is the one that keeps the ' green 

 bug' in control in normal years, and in 

 years when the latter is most abundant 

 finally over-comes it, as was the case in 

 1907 in Kansas, North Carolina, and other 

 States in the more northern part of the 

 range of the pest." 



" Unfortunately this parasitic "wasp"- 

 as with other beneficial insects is active 

 only while the temperature is above 56 F., 

 or at least 10 above that at which the 

 ' green bug' breeds freely; and herein is the 

 whole secret of the irregular disastrous out- 

 breaks of the ' green bug' in grain fields. 

 As accounting for the outbreak in the year 

 1907, the ' green bug' had had a whole 

 winter and the following late spring in 

 which to breed and multiply unmolested, 

 and it accomplished its principal damage, 

 as in Texas and southern Oklahoma,bef ore 

 the weather was warm enough for the para- 

 site to increase sufficiently to overcome it." 

 " As further illustrative of the import- 



FIG. 122. Dead "green 

 bugs," showing hole 

 from which the matu- 

 red parasite of Lysiph- 

 lebus emerges. The 

 top figure shows the 

 lid still attached, but 

 pushed back; the bot- 

 tom figure shows the 

 parasite emerging. 

 Enlarged. (After 

 Webster, U. S. Dept. 

 Agr.) 



ant bearing of weather conditions, it is found that in the case of 

 the three important outbreaks of this insect, namely, for the years 



