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Psyche 
[Vol. 88 
pheromonal communication system which facilitates group move- 
ments. In the membracids, there is indirect evidence for aggregation 
pheromones (Hinton 1976, 1977). Alarm pheromones of membra- 
cids are released only when the body wall is ruptured, and this type 
of release has not been reported for any other insects. Pheromones 
causing alarm responses are known to be present in at least 3 
membracid species. They are interspecific in action but have not 
been identified (Nault et al. 1974). 
This study reports an examination of the movements of G. solani 
aggregations on host plants with particular emphasis on the female’s 
behavior. 
MATERIALS AND METHODS 
MAINTENANCE OF INSECTS 
G. solani was collected from horse nettle growing in or near 
Raleigh, N.C., and aggregations were maintained for more than a 
year on horse nettle or eggplant either in the laboratory on a 16:8 
light: dark cycle or in a greenhouse. The movements of nymphs were 
studied after an aggregation consisting of nymphs and a female had 
been transferred to a small sprig of horse nettle having an un- 
branched stem with 5 or more leaves. A piece of leaf containing a 
group was pinned to the upper surface of the second or third leaf 
from the bottom of a horse nettle stem. In time, the aggregation 
moved off the leaf fragment and onto the fresh leaf. 
FEEDING MOVEMENTS 
Feeding movements were measured in light, darkness, and with a 
light placed below the aggregation. Groups chosen for these studies 
were nymphs in the third or fourth instars, with smaller numbers of 
the other instars present. For dark conditions, an aggregation on a 
horse nettle sprig was placed in a tightly covered metal can which 
had been sprayed inside with a dull-finish black paint. Directional 
lighting was provided by placing the sprig or plant within a 
darkened enclosure and positioning a light about 0.6 m from the 
bottom of the plant. 
ALARM RESPONSE AND ALARM PHEROMONE 
G. solani nymphs exhibited an alarm response after they were 
presented with a nymph, freshly squeezed and held by fine forceps, 
