1983] Blondehim & Frankenberg — Sounds of Grasshopper 3S9 
the size of the P. syriaca male, while adults could handle even the 
large female; the frequency spectrum of the sounds of P. syriaca falls 
within the hearing range of P. h. guttatus (Werner 1976); and 
finally, a laboratory stock of this gecko was available. Though wild- 
caught, the geckos had been kept in captivity in the vivarium for 
months to years. Though the memory span of this gecko species is 
not known, it may well be that the long laboratory incarceration 
had dimmed recollections of possible previous encounters with this 
grasshopper and its ruse. 
Experimental procedure: A series of three grasshoppers was 
introduced simultaneously into the cage of a gecko whose habitual 
diet of fly maggots had been removed at least a day previous: an 
untreated P. syriaca male, a silenced P. syriaca male and a fourth 
instar nymph of L. m. migratorioides. The insects were introduced 
at noon, prior to the peak activity hours of the gecko (Frankenberg 
1979), and observations were made every half hour from noon to 
5:00 PM and from 8:00 AM to noon. The first item eaten was 
assigned the number 1; the second item, 2; and the third, 3. If two 
grasshoppers disappeared between any two readings, both were 
assigned the same number. In the few instances in which all three 
grasshoppers were alive and apparently unharmed at the end of 24 
hours, it was assumed that the gecko was not hungry; the experi- 
ment was not included in tallying the results. After an interval of 
several days, the gecko was used again. Silenced P. syriaca were 
checked at the end of the experiment to ascertain that they were 
indeed still unable to produce sound. 
Results and Conclusions 
In the cages of the 26 geckos tested, no untreated P. syriaca was 
ever the first to disappear and 69% were never eaten at all. The 
silenced P. syriaca was eaten first in 46% and the L. m. migrato- 
rioides nymphs in 78% of the experiments (Table I and Fig. 1). A 
G-test (Sokal and Rholf 1969) was carried out to test for indepen- 
dence between the three choices of prey and the order of predation. 
It was found significant (G = 49.9; df = 6, p< 0.001). A sign test 
(Siegel 1956) between each of the three combinations of paired 
insects for all the 26 instances in which a grasshopper was eaten 
showed that silenced P. syriaca were eaten before untreated ones in 
18 experiments (p^O.002), L. m. migratorioides were eaten before 
