6 DECIDUOUS FRUIT INSECTS AXD INSECTICIDES. 



THE NYMPHAL STAGES. 



The young " hoppers," or nymphs, commence to appear about the 

 middle of June, and a close examination of the underside of infested 

 leaves at this time is likely to reveal a number of recently hatched 

 nymphs, at about the stage shown in figure 2, running actively over 

 the surface. In hatching from the egg the young ;; hopper " has to 

 force its way through the pubescence on the underside of the leaf, 

 and in doing so appears as a minute, whitish object, which, when 

 examined under a lens, is seen to possess a pair of red eyes. After 

 a few minutes of laborious struggling it forces itself to the surface 

 of the pubescence, where its legs and antenna? spread and become 

 disengaged and the tiny creature is ready to commence its destructive 

 operations. This it does by thrusting its tiny beaklike mouthparts 

 into the tissue of the leaf and extracting the juices. As the season 

 advances it is not uncommon to find individual leaves supporting 

 from 200 to 300 of these nymphs in the various stages of nymphal 

 development. 



As the nymph increases in size it casts or molts its old skin for a 

 larger one. There are five of these molts before the nymph reaches 

 the adult stage. The first four require a period of 5 days for each 

 molt, and between the fourth and fifth molts there is a period of 12 

 days. Hence about a month is required in which to complete the 

 nymphal period. Figure 3 represents a nymph after the fourth 

 molt with fully developed wing pads. 



The term "hopper" applied to this form of the insect is a mis- 

 nomer and is likely to create an erroneous impression concerning the 

 movements of the insect at this period of its life history. The 

 nymphs do not hop or leap, as the term " hopper " would imply, and 

 although they run about very actively on the underside of the leaf 

 and sometimes a few of them may be seen running down the stem of 

 the leaf and also upon its upper surface, it is doubtful if the journeys 

 of more than a very small percentage of them extend beyond the con- 

 fines of the leaf upon which the eggs from which they were hatched 

 were deposited. This limited area of movement of the insect during 

 this period of its life is exceedingly important from an economic 

 point of view, since it admits of its destruction during the more rapid 

 gTOwing season of the vine and at a period when there is slight 

 possibility of reinfestation of treated areas. 



THE ADULT. 



With the final molt and the full development and use of its wings 

 the adult leafhopper becomes an extremely agile and active creature, 

 leaping and darting rapidly from leaf to leaf at the slightest dis- 

 turbance, being much more active during the warm weather than on 

 cold, windy days, when it can be dislodged from its shelter under the 



