Progress 03/01/00 to 09/30/05
Outputs
Recent research has demonstrated that spiders can help control pest insects in agroecosystems. We have conducted one of the first set of studies on whether spiders are beneficial predators in greenhouses. Greenhouses are an important part of the agriculture of Massachusetts, which has over 200 certified growers (http://www.mass.gov/agr/farmproducts/plants/growers_certified.htm). We have focused on jumping spiders, which do not build webs but rather actively hunt prey. Because their potential as greenhouse predators has not been examined, our research includes generating basic knowledge of spider behavior as well as tests of their efficacy. First, it is important to know whether or not predators are likely to remain in the same home range from day to day. Predators that exhibit high site fidelity may require additional efforts in order to become established in the desired area. Once established, however, these species would be more likely to provide long-term control.
Therefore, understanding the movement patterns of predators is of value. We measured site fidelity in the field with mark-recapture techniques, and found that spiders with the highest site fidelity are adult females. Males, in contrast, were rarely site faithful. Spiders could easily be encouraged to colonize an area by providing inexpensive nest tubes constructed of plastic tubing. We also followed individual spiders as they were foraging, and found that males moved significantly further than females. Thus, females will be more useful in biocontrol than males, and the number of spiders in an area can be enhanced by the addition of nesting tubes. This work is in press in Animal Behavior. Second, we need to understand how a potential predator detects and identifies prey. A series of experiments confirmed that local jumping spiders rely on visual cues to detect prey. We found no evidence that jumping spiders, in contrast to wolf spiders, detect chemical cues from prey. Jumping spiders
responded to video images of prey, and were particularly sensitive to horizontal movements rather than vertical movements. This work resulted in one published paper in Journal of Arachnology and one in preparation, as well as a conference talk. Third, we need to understand how prey capture behavior is affected by experience. We found that the behavior of jumping spiders is malleable. They can learn to avoid distasteful prey. Further, we found that this behavior depends on the context: avoidance behaviors that spiders learn in one environment do not necessarily translate to a new environment. We are expanding this latter work, initially done in artificial situations in the laboratory, to environments more relevant to a greenhouse setting. This work has resulted in one paper in Behavioral Ecology and two in preparation. Fourth, we also conducted a study of the efficacy of spiders as biological control agents in a greenhouse. We found that a local jumping spider significantly reduced
damage on basil plants. This paper is in press at the Journal of Economic Entomology.
Impacts
This work has the potential to benefit the many Massachusetts growers who use greenhouses. Over 200 certified growers and nursery owners are in Massachusetts.
Publications
- Skow, C. and E. Jakob. 2005. Jumping spiders attend to context during learned avoidance of aposematic prey. Behavioral Ecology. 17:34-40.
- Hoefler, C., M. Taylor, and E. M. Jakob. 2002. Chemosensory response to prey in Phidippus audax (Araneae, Salticidae) and Pardosa milvina (Araneae, Lycosidae). Journal of Arachnology 30:155-158.
- Hoefler, C. and E. Jakob. 2006. The potential of a jumping spider (Phidippus clarus) as a biocontrol agent. Journal of Economic Entomology. In press.
- Hoefler, C. and E. Jakob. 2005. Jumping spiders in space: movement patterns, nest site fidelity and the use of beacons. Animal Behaviour. In press.
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Progress 10/01/03 to 09/30/04
Outputs
In recent years, research has demonstrated that spiders can help control pest insects in agroecosystems. We have been studying native spiders in the family Salticidae, or the jumping spiders. In particular, we have focused on the potential of jumping spiders to control pests in greenhouses. Greenhouses are an important part of the agriculture of Massachusetts, which has over 200 certified growers (http://www.mass.gov/agr/farmproducts/plants/growers_certified.htm). The usefulness of jumping spiders as biological control agents in greenhouses has not been previously examined, so our research includes generating basic knowledge of spider behavior as well as tests of their efficacy. First, it is important to know whether or not predators are likely to remain in the same home range from day to day. Predators that exhibit high site fidelity may require additional efforts in order to become established in the desired area. Once established, however, these species would be
more likely to provide long-term control. Therefore, understanding the movement patterns of predators is of value. We determined the frequency of site fidelity, which we defined as using the same nest site on consecutive nights with an intervening foraging bout. Using a mark-recapture technique, we found that spiders with the highest site fidelity are adult females. Males, in contrast, were rarely site faithful. Spiders could easily be encouraged to colonize an area by providing inexpensive nest tubes constructed of plastic tubing. We also followed individual spiders as they were foraging, and found that males moved significantly further than females. Thus, females will be more useful in biocontrol than males, and that the number of spiders in an area can be enhanced by the addition of nesting tubes. This work is in press. Second, we need to understand how a potential predator detects and identifies prey. A series of experiments confirmed that local jumping spiders rely on visual cues
to detect prey. We found no evidence that jumping spiders, in contrast to wolf spiders, detect chemical cues from prey. Jumping spiders responded to video images of prey, and were particularly sensitive to horizontal movements rather than vertical movements. This work resulted in one published paper and one in preparation, as well as a conference talk. Third, we need to understand how prey capture behavior is affected by experience. We found that the behavior of jumping spiders is malleable. They can learn to avoid distasteful prey. Further, we found that this behavior depends on the context: avoidance behaviors that spiders learn in one environment do not necessarily translate to a new environment. We are expanding this latter work, initially done in artificial situations in the laboratory, to environments more relevant to a greenhouse setting. This work has resulted in one paper accepted for publication and another in review. Fourth, we also conducted a study of the efficacy of
spiders as biological control agents in a greenhouse. We found that a local jumping spider significantly reduced damage on basil plants. This paper is about to be submitted.
Impacts
This work has the potential to benefit the many Massachusetts growers who use greenhouses. Over 200 certified growers and nursery owners are in Massachusetts.
Publications
- No publications reported this period
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Progress 10/01/02 to 09/30/03
Outputs
Here is a report of progress, organized according to the four goals of the proposal. A. Fidelity to retreat sites used at night We measured site fidelity by checking whether spiders were in their nests on consecutive nights after leaving the nest on the intervening day. We took advantage of the fact that spiders readily construct nests inside pieces of tubing. We set up a 30x30m grid of flags with nest tubes. After a 3-week colonization period, we collected spiders from nest tubes by gently squeezing the sides of tubes until they emerged. To identify spiders individually, we attached uniquely coded bee tags to the dorsal surface of the abdomen. We found high rates of site fidelity, with 50% of spiders returning to their tubes in July, and 90% in August. This suggests that spiders are likely to stay in greenhouses when placed there for predator control. B. Movement patterns and prey capture of foraging spiders (field and greenhouse studies) Of the many studies of
jumping spider behavior, only a handful have been conducted in the field. One of the main goals of this project is to learn about the distance that jumping spiders move in the field. We measured spider movement by conducting focal observations of individuals in the field. An observer walked slowly through the fields until he or she saw a Phidippus clarus. The observer then followed the spider for a minimum of 5 and a maximum of 15 minutes, or until it was lost from view. We placed a flag at the location of the spider when the trial began, and a second at its location at the end of the trial, and used these to measure net distance travelled. We recorded behaviors on a microcassette recorder, and scored the tapes with behavioral data analysis software. We found that spiders moved surprisingly long distances, up to 20 m in 15 m. Males moved significantly further than females. Females were more likely to feed. These results suggest that (1) the home range of spiders is large enough so
that they may effectively cover a large greenhouse and (2) females would be more effective control agents than males. C. Sensory capabilities of salticids Work on chemical cues of salticids was reported previously. Use of visual cues in prey identification is in progress. D. Learning in salticids We made a discovery not previously documented for spiders: predatory behavior is context dependent. Spiders that learn to avoid bad-tasting prey in one location forget that response in a new location. This is very interesting for the greenhouse system, as it implies that the reverse may be true: spiders that learn that some plants have prey may favor that plant in foraging. We also discovered that spiders learn landmarks affiliated with their nests, and can even learn landmark colors. E. Testing the efficacy of salticids as predators in a greenhouse setting (greenhouse study) This was previously reported.
Impacts
This is the first study, to our knowledge, to consider the impact of jumping spiders on pests in a greenhouse setting. The combination of field data on spider life history, along with experiments in the greenhouse, will establish the circumstances under which spiders may be beneficial.
Publications
- No publications reported this period
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Progress 10/01/01 to 09/30/02
Outputs
This year, we focused on two goals of the Hatch project. 1. Testing the efficacy of salticids as predators in a greenhouse setting (goal E in original proposal). Spiders have been investigated as biocontrol agents in field settings, but not, to our knowledge, in greenhouse settings. We tested salticids, which rely on acute vision to stalk prey rather than building a web, and thus are potentially capable of controlling flightless pests. We used Phidippus clarus, a common salticid found locally. Our test crop was basil, which is grown commercially in large greenhouses in the Amherst area. We focused on one pest, mirids, herbivorous insects that will feed on a wide variety of plants. Mirids damage plants by inserting their beak-like mouthparts into the leaf and extracting the juices. The potential of these insects to induce considerable damage to crop plants and their palatability to P. clarus in the field make mirids a good choice. Five 0.3 m basil plants were
positioned 15 - 20 cm apart in each of 8 cubic meter enclosures. Three treatments were randomly assigned: two control cages with neither pests nor spiders, three with only pests, and three with pests and spiders. In the 6 enclosures with pests, sixty mirids were introduced, and left for one week. Ten spiders were then introduced to each of the three cages designated to have them. After one additional week, we measured chlorophyll content with a chlorophyll meter (yielding SPAD-501 readings) on 4 randomly selected leaves on each plant, and recorded plant height. Basil plants in the pest-only treatment were significantly shorter than plants in the control and spider/pest treatments (P < 0.03). Control and spider/pest treatments did not significantly differ, suggesting that spider control of the pest was effective. Chlorophyl counts were higher in the pest-only treatment, but not significantly so. This experiment suggests that spiders may be used effectively to control greenhouse pests.
It suggests that jumping spiders can find even relatively immobile prey. It also suggests that one possible drawback with the use of spiders as control agents, their propensity to cannibalism, may be overcome: we saw no evidence of cannibalism in our cages. The commonness of jumping spiders (we have easily netted over 40 P. clarus per hour) makes them relatively easy to capture and introduce into a greenhouse. 2. The role of learning (goal D in original proposal) whether or not a predator has the ability to learn has implications for biocontrol. For example, animals that learn to recognize particular prey may then capture that species more often than would be expected by chance. This may cause problems if a learned prey species is not a pest. In other cases, predators may learn to search for prey on particular plant species, and this can again work against biocontrol efforts if a non-crop species is learned. Last year we documented that the predatory behavior of spiders can be
modified by experience. This year we are working on a study, still in progress, of the contextual cues that are important influences on learning.
Impacts
We completed the first test, to our knowledge, of the potential of spiders as biocontrol agents in a greenhouse settings. We found that jumping spiders reduced plant damage.
Publications
- No publications reported this period
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Progress 10/01/00 to 09/30/01
Outputs
We have finished much of the field work and several of the laboratory experiments proposed. We have now characterized the natural movements of spiders in the field, important for determining their efficacy as greenhouse control agents. We have found that females are much more site faithful than males, and site fidelity increases as the season progresses. We have also measured movement rates of two species of spiders in the field; these data are still being analyzed. We have also documented the use of landmarks by spiders in the field. Finally, we have shown that spiders can learn to avoid unfavorable prey.
Impacts
The project has social impact in several ways. First, it provides research experiences for undergraduates. This project provides data about the efficacy of spiders as control agents in greenhouses, which isuseful for growers.
Publications
- No publications reported this period
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Progress 03/01/00 to 09/30/00
Outputs
We have made significant progress on two goals. In goal A, we began field studies on retreat site reuse, which is an important step in understanding space use in jumping spiders. We worked in an old field in Amherst, MA. Artificial nesting tubes (black rubber tubes, approximately 4 cm in length) were placed in the vegetation. Thirty-five tubes were placed in five rows. Tubes were separated by 2 m. Tubes were checked twice daily, at mid-afternoon and dusk. If a retreat was occupied, the sex and species of the spider were noted, and the spider was given an individual mark with nontoxic paint. Four species of salticids used the tubes: 12 juvenile Phidippus audax, 12 adult female P. clarus, 7 Pelegrina sp., and one Eris militaris. We found that species differ in whether they return to tubes. Phidippus audax and P. clarus returned to the same tube for an average of 4.67 and 5.08 consecutive days, respectively. Pellegrina sp. rarely returns to tubes (average 1.0 day), and
the single E. militaris did not return to its tube. These preliminary results suggest that these species have different levels of site fidelity, and thus will be differently suited for biological control in a greenhouse. This experiment will be expanded greatly next summer. We also completed Goal 2, part b. We conducted the first test, to our knowledge, of the ability of jumping spiders (Araneae, Salticidae) to use chemical cues of prey to adjust their foraging behavior. Specifically, we examined the effects of substratum-borne chemical cues of prey on the amount of time invested in a given patch in the jumping spider Phidippus audax. We compared our results (and tested our protocol) using the wolf spider Pardosa milvina (Araneae, Lycosidae) because other wolf spiders have been demonstrated to respond to chemical prey cues on substrates. We found that wolf spiders spent more time on filter paper scented with crickets, whereas jumping spiders spent equal amounts of time on scented and
control papers. Thus, we found no evidence that jumping spiders rely on chemical cues for foraging. This work is in review: Hoefler, C., M. Taylor, and E. M. Jakob. In review. Chemosensory response to prey in Phidippus audax (Araneae, Salticidae) and Pardosa milvina (Araneae, Lycosidae). Journal of Arachnology.
Impacts
This research will generate valuable data on the efficacy of salticids as biological control agents in a greenhouse setting. As planned, the first few years of the project are taking place in a field and in the laboratory. In addition, part of the work (goal B above) was done in collaboration with a minority undergraduate student in a summer program here. She is second author on the manuscript.
Publications
- No publications reported this period
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