THE SHAEP-HEADED GKAIN LEAFHOPPEK. 13 



HATCHING OF THE EGGS. 



The emerging nymphs burst the end of the eggshell irregularly and 

 emerge head first. Eggs deposited in the leaves hatch sooner than 

 those in stems, as there is not so much plant tissue covering them. 

 Those in stems appear to be inserted more deeply into the plant. 

 The nymphs issue at about the same time, irrespective of the posi- 

 tion of the eggs in the pocket. 



MOLTING OF THE NYMPHS. 



The fourth molting of a nymph was minutely observed, the whole 

 operation taking 20 minutes. The old skin split dorsally along the 

 head and thorax. The head of the nymph first came out, slowly fol- 

 lowed by the thorax and abdomen. The abdomen was pulled for- 

 ward through the old abdominal skin and put through the thoracic 

 slit. As the nymph gradually emerged it leaned or threw its weight 

 backward until the tip of its abdomen was nearly out; then it shifted 

 and spread its legs, taking a firm hold on the leaf surface. After com- 

 pleting the molt it remained still for several minutes. 



In examining the last-molt nymphal skin an indication of sex was 

 discovered. Outlines of the ovipositor or genitalia were quite promi- 

 nent and plain on this cast skin. Attention was then directed to the 

 examination of the last-instar nymphs, and it was found that there is 

 a sex indication with all nymphs of the fifth instar, as the distinction 

 between the male and female genitalia could readily be recognized. 

 (See fig. 1, i, j.) No sex indications appear in the nymphs of the 

 fourth instar. 



ADAPTABILITY OF SPECIES TO CHANGE OF FOOD PLANT. 



Only the nymphs of the last two instars can adapt themselves to a 

 change of food plants to any extent. This fact offers a suggestion in 

 the control of the species, in that cutting or grazing their food at the 

 time the nymphs are young will tend to starve them, and thus many 

 will be destroyed. 



However, the adults find no difficulty at all in a change. If their 

 food plants be destroyed or cut down, they immediately hunt for sub- 

 si it uf.es. Starving the adult3 in the fields would be next to impossible. 



MIGRATION. 



The species docs nol spread itself throughout one field or into other 

 fields by the dissemination of the young nymphs, but almost wholly 

 by the flight of the adults. The latter migrate freely from one 

 field to another in search of attract ive areas for food and oviposit ion. 

 Bi ides this, Prof. Osborn remarks: 1 "The insect shows at times a 

 distinct habit of migration at night." They have been reported 



lOp.cIt., p. 69. 



