Enhancement of resource finding efficiency by visual stimuli in Musca domestica (Diptera: Muscidae)

In complex natural environments, flies must simultaneously perform many behaviors such as food search, mate location, or predator avoidance. The concurrent per formance of multiple behaviors may affect the efficiency with which any one task is per formed. House flies commonly land near and pounce on other flies or fly-sized dark objects. We measured the effect of fly-like visual models on food foraging behavior. After consum ing a 1 julI drop of 0.25 M sucrose, the success of flies at locating a similar drop located adjacent to a fly-sized model at varying distances from the original drop was measured. The presence of the model greatly increased the proportion of flies able to locate a sucrose drop near the model, and reduced the time to find the additional resource. The effect diminished as distance between the first and second sucrose drops increased. The response to fly-like objects may, thus, facilitate interactions among flies (e.g., mate finding) and at the same time increase the probability of locating patchily distributed and cryptic resources. In nature, local search is performed under complex and varying conditions. Animals may alter their performance of local search in response to environmental stimuli. These conditions may impinge not only on local food search, but may simultaneously elicit responses appropriate to other behavioral systems, such as mate acquisition. For example, house flies, Musca domestica, commonly land near dark objects, and frequently pounce on these if they are three dimensional and approximately fly sized. This phenomenon has been described predominantly for males, and is assumed to be a mani festation of courtship or mating behaviors (Rogoff et al., 1964). Local search behavior following ingestion of a sucrose drop has been studied extensively for M. domestica (e.g., White et al., 1984) as have the parameters that define local search pathways (e.g., Collins et al., 1994). Local search behavior as a strategy for locating aggregated (patchy) resources has also been examined (Murdie and Hassell, 1973; Fromm and Bell, 1987). However, these studies have been conducted in very simple environments without conflicting or complementary stimuli. We tested the effect of potential interactions between internally generated local search behavior and re sponses to visual stimuli (unrelated to food) on the success of food resource location in M. domestica. Materials and Methods A laboratory colony of M. domestica was initiated from flies obtained from Carolina Biological Supply Co. Pupae from this colony were placed individually in 38-ml plastic cups. Food (powdered milk and sucrose) and water were available ad libitum. Adults remained isolated to preclude interac tions with other flies that may reduce overall vigor. Flies were tested 6-10 days postemergence. Forty eight hours before testing, adults were transferred to vials containing only water. All tests were conducted in a circular arena (75 cm diam) with a white floor surrounded by white walls (30 cm high) to minimize visual stimuli. Sucrose-drop finding is apparently random with respect to external cues in this context, and neither visual nor olfactory cues are used. All tests were conducted at 25? C, 70-80% RH and 2000 lux. We examined the relationship between local search for food resources and the tendency of flies to pounce on fly-sized three-dimensional objects. The success of local search in the absence of external stimuli was compared to success in the presence of a fly-sized model. A 1-ul drop containing 0.25 M sucrose was placed in the center of the arena. A second sucrose drop of equal volume and concentration was placed 2.5 to 20.0 cm distant from the first drop. In alternate tests, a 4-by-8-mm model made of black modelling clay was placed 1-2 mm from the second drop. Flies were first guided to the center drop using an inverted 45-ml clear plastic vial (10-cm-high by 3.5-cm-diameter). The vial was removed 1 Current address: Department of Plant Science, 247 Northern Plains Biostress Laboratory, Box 2140C, South Dakota State University, Brookings, SD 57007 Accepted for publication 8 February 1996. This content downloaded from 207.46. 13.52 on Fri, 21 Oct 2016 05:51:03 UTC All use subject to http://about.jstor. org/terms VOLUME 69, NUMBER 2 205