524 The University Science Bulletin. 



the last one on June 23, while they reached their maximum abun- 

 dance between May 11 and May 16. Second-instar nymphs ap- 

 peared May 4, reached their maximum number about May 18 to 

 May 27, and disappeared around June 20. Third instars were first 

 taken about May 11, were most abundant from May 29 to June 3, 

 while fourth instars appeared about May 16 and reached the maxi- 

 mum from June 7 to June 10. The first fifth instars were taken on 

 June 2. They were most abundant from June 13 to June 20 and 

 began to thin out by June 27, the last two being taken on July 4. 

 The average total of days for the nymphal stages is perhaps forty- 

 five days. 



HABITS OF NYMPHS. 



• 



Perhaps the first thing of interest to note about the nymphs is 

 their restlessness in the laboratory and their agility in moving 

 around. Since they are always found in spittle masses, it is only 

 natural to think of them as being rather inactive, helpless larvae, 

 but such does not appear to be the case. The first-instar nymphs 

 especially are most active. In fact one of the greatest difficulties 

 to overcome in the rearing of these insects was the continual moving 

 of the first instars. When collecting, if the larva were brought away 

 undisturbed in their spittle masses they usually were found missing 

 on arriving at the laboratory. A satisfactory method of taking 

 them is to wrap the plants in an improvised envelope of newspaper 

 and carry them away in this fashion. When the nymphs are trans- 

 ferred to new plants it takes them some time to become settled. 

 They ramble aimlessly over the plant, seemingly looking for the 

 most favorable feeding ground. In one instance a nymph was 

 observed which wandered the entire length of the stem and back 

 again, then out on the leaf, where it rambled all over the surface, 

 and even hung poised in the air, walking on the extreme margin of 

 the leaf. During this wandering period they repeatedly fall off the 

 plant on the dirt, where, if they happen to light on their backs, they 

 struggle to regain their feet, and usually perish in the attempt. They 

 dry up very quickly if not living in their spittle masses. Many times 

 they crawl from the plant to the ground and reach the surface of the 

 glass globe, where ensues a struggle to climb up the slick glass. 

 Several times during their wanderings the first instars have dis- 

 appeared entirely, crawling through two thicknesses of cheesecloth. 

 This restlessness of the nymphs is apt to be incited in two ways, 

 namely, by disturbing them in the spittle mass and because of lack 

 of juice from the plant. While looking for molted skins it was 



