1969] 
Davis and Russell — Commensalism 
269 
avocado buds than on either of the 2 food sources which occurred 
most frequently in the spider webs. The adults’ life expectancy was 
lowest on avocado buds also; being more than halved in the case of 
the average male. There appeared to be little difference in the utiliza- 
tion of Drosophila or honeysuckle by either nymphs or adults. 
The spider-mirid relationship appeared to be a case of commen- 
salism, since from all indications, the mirids neither damaged nor 
benefited the spiders but obtained food killed by the spider or caught 
in its web and were provided by the spider with a substrate which 
afforded some protection from rain and wind as well as from pred- 
ators. According to Carvalho (1954), Ranzovius fennahi in Trini- 
dad was predacious on spider eggs. There are several indications 
that such a predacious habit did not occur with R. moerens\ the 
small number of eggs laid by one agelenid spider compared to the 
large number (up to forty) of mirids observed in a single web, the 
tending of the egg sac by the spiders, and the observed feeding of 
the mirids on other food and not on the egg cases. 
References Cited 
Bristowe, W. S. 
1941. Comity of Spiders. 2: 334-338. The Ray Society, London. 
Carvalho, J. C. M. 
1954. Neotropical Miridae, LXVII : Genus Ranzovius Distant, pre- 
dacious on eggs of Theridion (Araneida) in Trinidad (Hemip- 
tera). Ann. & Mag. Natural History (7)74: 92-96 Illus. 
Gertsch, W. J. 
1949. American Spiders. D. Von Nostrand, N. Y. & London. 
Worth, C. B. 
1967. A Naturalist in Trinidad. J. B. Lippincott Co., Philadelphia & 
N. Y. pp. 138-147. 
Yonke, T. R. and J. T. Medler 
1965. Biology of Megalotomus quinquespinosus (Hemiptera: Alydidae). 
Ann. Entomol. Soc. Amer. 58: 222-224. 
