Wasp Size and Prey Load in Cerceris fumipennis (Hymenoptera, Crabronidae): Implications for Biosurveillance of Pest Buprestidae

Abstract

The relationship between predator and prey size was studied in the buprestid hunting wasp Cerceris fumipennis Say in eight widely distributed nesting aggregations in North Carolina, USA. Initial work indicated a significant linear relationship between wasp head width and wasp wet weight; thus, head width was used to estimate wasp body mass in subsequent studies. Prey loads of hunting females was studied by measuring the head width of the wasp, then identifying and weighing the prey item brought back to the nest. There was significant variation in wasp size among nesting aggregations; the average estimated wasp body mass in one site was double that in another. Prey weight varied with wasp weight, but larger wasps had a slight tendency to carry proportionally larger prey. Beetles captured by large wasps (≥120 mg) were significantly more variable in weight than those taken by small wasps (<80 mg). All but the smallest wasps could carry more than their own body weight. Prey loads ranged from 4.8⁻150.2% of wasp weight. Evidence suggests that small wasps bring back more of the economically important buprestid genus Agrilus and thus would be most efficient in biosurveillance for pest buprestids.

Keywords: Agrilus; emerald ash borer; flight load; insect survey; invasive pests; nest provisioning; prey.

Figure 1

A linear relationship between head width and body mass (wet weight) in Cerceris fumipennis (P < 0.001) at one North Carolina site.

Figure 2

Relationship between predicted wasp weight and prey beetle weight in hunting Cerceris fumipennis. (A) Prey beetle weight as a function of wasp weight. The relationship is best described with the equation: Beetle wt. (mg) = –59.19378 + 1.3317934 * Wasp Wt. (mg) + 0.0037293 * (Wasp Wt. (mg) − 103.066)²; R = 0.55, p < 0.0001. (B) Percent body weight (prey load) carried by C. fumipennis females ((beetle weight/wasp weight) × 100)). Points above the line indicate females carrying more than their own body weight. Data point 1: smallest prey load (4.8%, a wasp weighing 72.3 mg carrying a 3.5 mg Agrilus subrobustus); data point 2: largest prey load (150.2%, a wasp weighing 125.8 mg carrying a 188.9 mg Buprestis rufipes); data point 3: smallest wasp carrying more than her own body weight (113.6% prey load, a wasp weighing 57.2 mg carrying a 65.0 mg Buprestis maculipennis).