Daily energy intake and expenditure of the weaver ant Polyrhachis simplex (Hymenoptera: Formicidae) collecting honeydew from the cicada Oxyrrhachis versicolor (Homoptera: Membracidae)

Abstract

The weaver ant Polyrhachis simplex inhabits areas characterized by high ambient temperatures and Homoptera-hosting plants. Its main source of food is honeydew excreted by several species of Homoptera. We estimated the daily energy expenditure of P. simplex and measured its food and energy intake when it attended the cicada Oxyrrhachis versicolor. In addition, we estimated the energy intake and output of a population of weaver ants. The study was made on a single tamarisk tree (Tamarix mannifera) which had an ant nest at its base. There were 750 ants collecting honeydew on the tree and there was a ratio of ants:cicadas of approximately 1:1. Each ant made six trips from the nest to the cicada clusters and each trip required approximately 2 hours. Daily energy expenditure per ant was 1·51 to 1·68 J and the total expenditure for all 750 ants was 1·13 to 1·26 kJ/day. Honeydew intake per trip was 0·54 mg dry matter or 10·51 J, and the total energy brought into the nest was 37·37 kJ/day. Total energy expenditure of the ants was only 2·4 to 2·7% of the total intake and 97 ·3 to 97·7% remained for social life and for larval development and queen reproduction. We concluded that weaver ants developed an extremely efficient foraging system, expending only a small fraction of their energy intake on foraging.