THE SHARP-HEADED GRAIN LEAFHOPPER. 11 



jump at the slightest provocation. Because of this fact they are 

 readily caught in the hopperdozer. A clump of tall grass was 

 observed one day to be almost alive with adults, and although there 

 was no wind and apparently nothing to disturb them, the adults 

 suddenly hopped away, all at once. What caused the alarm was not 

 determined. Adults, as well as nymphs, have the habit of dodging 

 to the opposite side of a leaf or stem when approached by a foreign 

 object. On days when there is a strong wind they remain in hiding 

 close to the ground. They are most active during midday, and 

 seldom may they be seen hopping about when dew is on the plants. 

 As the sunlight recedes in the late afternoon they seek shelter under 

 dried leaves and refuse, and at the base of the plant stems. While 

 adults are most active on warm sunny days, during the intense heat 

 of the summer they seek shade and damp places. From a series of 

 observations it has been noted that they are more active on sunny 

 than on cloudy days. Many adults, but not in such numbers as 

 nymphs, can often be found feeding or resting on the same stem or 

 leaf. They both rest and feed with head upward on the plant. 



GENERAL ACTIVITIES OF THE NYMPHS. 



Nymphs are even more active than adults, doing more running 

 and dodging and less jumping about the plants. They seem to group 

 themselves together; oftentimes 15 to 20 nymphs can be found on 



1 square inch of leaf surface, and it is because of this that their 

 feeding becomes injurious to the plant. Mr. Wildermuth has ob- 

 served that the nymphs commence feeding immediately after hatch- 

 ing. The wind has a stronger effect upon the nymphs than upon 

 the adults, and oftentimes a gust of wind will blow the nymphs 

 several yards. They attempt to keep out of the wind by hiding 

 but are rather easily blown from one plant to another, the throats of 

 young corn plants making a favorite hiding place. When resting the 

 first-instar nymph assumes a characteristic posture, carrying its 

 abdomen slightly curled up and over. The nymphs are very sensi- 

 tive 1o heat, and the direct rays of the sun for more than a minute or 

 two on hot days will kill these young stages. Many times they have 

 been observed 1<> burst a bubble of excreta from the tip of their abdo- 

 men when disturbed or approached by a foreign object, and Mr. 

 Wildermuth suggests that this may be a means of defense as it is in 

 the case of nymphs of (he three-cornered alfalfa hopper {Stidoce/pliala 



OPPOSITION. 



A few days after the male and female adults have emerged from 

 the jiist iiviii|>h;iJ moll copulation has been noted to take place. 

 In L0 experiments carried on in confinement (lie male died within I and 



2 days after copulation, although the females, in the same cxperi- 



