Section I: UNEP- WCMC Weblink Information


Project Title:  Forest Caterpillars


Principal Investigator: Lee Dyer

Position/Affiliations: Professor, Tulane University

E-mail address:                               

Research Sites and Local Management Status:

Napo, Ecuador, -0.583, -76.13, Biological Reserve, National Park

Sarapiqui, Costa Rica, 10.4, -82.0, Biological Reserve, National Park

Arizona, USA, 31.88, -109.2, Biological Reserve, National Forest


Scientific names of primary species being studied (if appropriate):

Lepidoptera, Hymenoptera, Diptera, Angiosperms, Nemata


Key Research Objectives (5-8 brief bullet points):

·         What affects diversity and abundance of caterpillars and parasitoids in natural forests and adjacent agriculture (banana and alfalfa)?

·         What parasitoids might be good candidates for biological control in banana plantations and alfalfa fields?

·         How do variation in precipitation and temperature affect levels of parasitism (and subsequently affect caterpillar densities)?


Date this report was completed: January 29, 2006


Data Collection and Results

Diversity relationships

One objective of our Earthwatch caterpillar research was to determine the effects of plant-herbivore-predator interactions on biodiversity. We measured grassland plant and insect diversity at our Arizona site to document patterns of diversity at multiple trophic levels. The study sites included unmanaged pasture intermixed along riparian forest, and cattle grazed pasture with flood irrigation. We found that plant abundance and richness were higher on the grazed-irrigated pasture versus the unmanaged field. Structural equation models revealed strong effects of herbivore (including caterpillars) diversity on diversity of other trophic levels (mostly parasitoids). For the grazed fields, top-down forces were important, with enemy diversity depressing herbivore diversity, which in turn depressed plant diversity. For the unmanaged fields, bottom-up forces dominated, with plant diversity causing increased herbivore diversity, which in turn increased enemy diversity (Figure 1). For all fields, detritivore diversity was enhanced by overall arthropod diversity. Increasing productivity (i.e. adding fertilizer) caused increases in detritivore numbers, but lower diversity. These results support hypotheses from other empirical studies that changes in diversity of a single trophic level can cascade to effect diversity at other, nonadjacent trophic levels. Understanding such diversity relationships across ecosystems is necessary for directing management of these systems.






Figure 1. Path diagrams based on analyses of Earthwatch plot data, as well as experimental data from managed and unmanaged grasslands. Arrows indicate positive effects, lines with a circle-head indicate negative effects. Numbers next to effects are values of significant path coefficients and indicate the size of the effect. H’ = arthropod diversity, ni = arthropod abundance.



Climatic unpredictability and parasitism of caterpillars: implications of global warming

Numerous Earthwatch teams quantified parasitism at our research sites in Louisiana, Ecuador, Costa Rica, and Arizona. Our most significant finding is relevant to the hypothesis insect outbreaks will increase in frequency and intensity with projected changes in global climate through direct effects of climate change on insect populations. While there is much concern about mean changes in global climate, the impact of climatic variability itself on species interactions has been little explored. We combined data from our 4 Earthwatch sites with 11 additional sites that covered a broad gradient of climatic variability and found a decrease in levels of parasitism as climatic variability increases (Figure 2). The dominant contribution to this pattern by relatively specialized parasitoid wasps suggests that climatic variability impairs the ability of parasitoids to track host populations. Given the important role of parasitoids in regulating insect herbivore populations in natural and managed systems, we predict an increase in the frequency and intensity of herbivore outbreaks through a disruption of enemy-herbivore dynamics as climates become more variable.


Figure 2. A linear regression of total parasitism levels of caterpillars from fifteen extensive rearing programs against year-to-year variability in precipitation (CV; R2 = 0.33). Letter codes correspond to sites of rearing studies; AZ = Arizona, USA; ACGd =  Guanacaste Conservation Area, Costa Rica, dry forest; ACGr = rain forest; LS = La Selva Biological Station, Costa Rica; YBS = Yanayacu Biological Station, Ecuador; NO = Southeast Louisiana, USA; Braz = Reserva Ecológica do IBGE, Brazil; BCI = Barro Coloardo Island, Panama; PNM = Parque Nacional Metropolitana, Panama; FS = Fort Sherman, Panama; Can = Southern Ontario, Canada; MD = Maryland, USA; MO = Southern Missouri, USA; VA = Virginia and West Virginia, USA.


Predicting caterpillar parasitism in agricultural systems

Leaf damage caused by Lepidoptera as they are responsible for the majority of the herbivory suffered by rainforest plants as well as many agricultural systems, including banana plantations. We used Earthwatch parasitism data to link ecological theory to the biological control of insect pests in banana plantations. Through our established predictive approach, ecological data on plant-caterpillar-parasitoid interactions from natural systems were used to formulate simple recommendations for biological control in banana plantations. The specific goals were (1) to determine the most effective parasitoid enemies for biological control of caterpillars in banana plantations and (2) to examine the impact of nematicides on enemy populations. To assess percent parasitism,we reared 1,121 caterpillars collected from six plantations managed under two nematicide regimens. Attack by parasitoids in the families Tachinidae (Diptera), Braconidae, Eulophidae, and Chalcididae (Hymenoptera) closely paralleled rates reported for species with similar characteristics at our Earthwatch site at La Selva, and statistical models predicted the relative importance of these parasitoids as sources of mortality. We found that tachinid flies were the most important source of early instar larval parasitism in banana plantations, and their importance increased with more intensive nematicide applications. The statistical models that we derived from data at La Selva were useful in predicting which parasitoids would be important in banana and which larval characteristics they would preferentially attack. We provided predictions for caterpillars that can occur in other banana plantations (Table 1), especially those that shift from insecticide use to biological control. This approach could be used in other managed ecosystems (e.g., near our sites in Ecuador and Arizona) where the identification of effective biological control agents is needed.



Table 1. Percent parasitism predictions (with SE in parentheses) for common species of Lepidoptera found in Costa Rican banana plantations based on logit models from Earthwatch data collected over the past 10 years. Parasitism levels over 30% are likely to result in successful biological control.



Significance/Benefits of Research

Diversity and natural history

Our most significant accomplishment is the compilation of natural history data related to approximately 2800 species of caterpillars, plants, and parasitoids. We share this natural history information with locals and scientists alike (refer to the list of talks and publications), including talks in Spanish to Costa Rican and Ecuadorian students, naturalists, and local workers; the local talks have increased awareness and respect for insect diversity. Many of the naturalist guides at our research sites now point out caterpillars in their tourist walks and discuss the role they play in the forest. We also share these data with anyone who has internet access by publishing it on caterpillar web pages at The web pages are currently undergoing major improvements and should be a very useful tool for managing and studying biodiversity for many years to come. In addition, our basic research on diversity relationships between trophic levels will contribute to a growing understanding of how parasitoids and other natural enemies affect entire biotic communities.


Sustainable agriculture

Managers of banana plantations, alfalfa fields, and other agricultural systems who are attempting to control pests without using pesticides will benefit from increased knowledge of the parasitoid community. First, we discovered at least 12 new species of parasitoids (that are still being treated by taxonomists) in the families Braconidae and Tachinidae, all of which are potentially important biological control agents. Second, our modeling approach identified the most important biological control agents in banana plantations under different pesticide management, which allows plantation owners to manage for caterpillar pests without resorting to harmful insecticides.


Sustainable employment in the rainforest

Although it is not a direct benefit from the research, our Earthwatch project benefits the local communities by supporting the research stations and by continuing collaborations with local naturalists and scientists. Field stations generally benefit the local community by providing excellent employment opportunities that are not destructive to the forest and by boosting the local economy. At the Costa Rica site, we continue to provide long-term employment to local naturalists, Gerardo Vega and Humberto Garcia; at the Ecuador site, we have provided long-term employment to at least 3 full time field assistants. We plan to continue hiring as many local naturalists as possible, depending on continued funding from other sources.


Environmental education

Finally, our work has directly benefited the educational community because many volunteers have been school teachers and have incorporated ideas learned from this project into their classes. It has indirectly benefited the educational community because the research addresses basic theoretical questions in ecology. One of the most important issues to which our Earthwatch project has contributed is the idea of “trophic cascades.” Theory predicts that the effects of predators and parasitoids on plant biomass and diversity should not be great in complex systems such as rainforests, but we have demonstrated that the enemies of caterpillars significantly enhance plant biomass and diversity by killing caterpillars. This means that the consequences of tropical predator extinctions are more severe than previously thought, and predators of all sizes and all predatory guilds (i.e. including parasitoids) should be a major focus for conservation efforts.


Dissemination of Results (all publications below are available in pdf format at:


Peer reviewed articles and book chapters

Stireman III, J.O., L.A. Dyer, D.H. Janzen, M.S. Singer, J.T. Lill, R.J. Marquis, R.E. Ricklefs, G.L. Gentry, W. Hallwachs, P.D. Coley, J.A. Barone, H.F. Greeney, H. Connahs, P. Barbosa, H.C. Morais, and I.R. Diniz. 2005. Climatic unpredictability and caterpillar parasitism: implications of global warming. Proceedings of the National Academy of Sciences 102:17384-17387.


Dyer, L.A., Matlock, R.M., Cherzad, D., and R. O’Malley. 2005. Predicting successful biological control in banana plantations. Environmental Entomology 34:403-409.


Stireman, J.O. III, Dyer, L.A., and R.M. Matlock. 2005. Top-down forces in managed versus unmanaged habitats. Pages 303-323 in: Barbosa, P. and I. Castellanos (eds.). Ecology of Predator-Prey Interactions. Oxford University Press, Oxford.


Letourneau, D.K. and L.A. Dyer. 2005. Multi-trophic interactions and biodiversity: beetles, ants, caterpillars, and plants. Pages 366-385 in: Burslem,D.F.R.P.; Pinard,M.A.; Hartley,S.E. (eds.). Biotic Interactions in the Tropics: Their Role in the Maintenance of Species Diversity. Cambridge University Press, Cambridge, UK.


Irschick, D., Dyer, L.A., and T. Sherry. 2005. Phylogenetic methods for studying specialization. Oikos 110:404-408.



Organization for Tropical Studies, Costa Rica, 2005

Yanayacu Biological Station, Ecuador, 2005

Indiana University, 2005

Ecological Society of America, Annual Meetings, 2005

University of California Davis, 2005

Bodega Marine Laboratory, 2005

Mesa State College, 2005

Rice University, 2005

University of Kentucky (Graduate Student Select Speaker), 2005

Louisiana State University, 2005


Section II:  Volunteers

February 3, 2006

Dear Volunteers,   

While I write this letter from a FEMA trailer (without electricity), I am reflecting on a year that was filled with ups and downs. The last 5 months have been difficult for everyone in New Orleans, including our laboratory. (I created a webpage with information on how Katrina affected the lab: However, despite the problems, last year was definitely highlighted by our trips to the field and our interactions with all of you. I really hope the final report provides you with a sense of how successful the Forest Caterpillars project has been because of your excellent field assistance. I am also excited to report that we have started our New Orleans Earthwatch teams, and these volunteers are helping us get back on our feet in the laboratory while also studying the effects of hurricanes on caterpillar-parasitoid interactions. For pictures of your team and a few of your caterpillars, visit this web page:

I have been impressed with the amount of high quality data that Earthwatch volunteers have collected with us over the past 9 years. I am sure that I will continue leading this research for at least 20 more years, and I hope to keep discovering new species and new associations. Perhaps the most important paper that we published from these data was our paper in the Proceedings of the National Academy of Sciences in November (2005 – the paper is available here: We discuss how extreme weather events (like hurricanes) cause a decrease in parasitism – this means that increases in extreme weather events as a result of climate change may cause parasitoid extinctions and increases in caterpillar outbreaks in forests and agricultural systems. We hope that this paper helps land managers plan for future conservation of natural enemy communities.

If you are wondering about the rest of the team of plant/caterpillar/enemy investigators, feel free to send an email asking for their addresses. Unfortunately, Marco and Santiago had to leave the Ecuador project, but we hired several new gusaneros: Maria, Rafael, and Wilmer. They are doing a fantastic job. Beto, Gerardo, Grant, Angela, Tara, Clark, and Michael are still working full-time with me on various projects, including the caterpillar work. Everyone who lived in New Orleans before the hurricane is back and all of us have at least temporary housing. John Stireman started a faculty position at Wright State University and will be with the team in Arizona again this year. Harold Greeney is still up in the cloud forest chasing after butterflies, helping researchers, and transforming Yanayacu into a major research center – the station now has a hydroelectric plant that provides full time electricity. Camden started kindergarten this January, after travelling the country with his mom for four months.

I would like to thank all of you for your hard work. As an extended team, we have a strong database and positive memories of great people. My collaborators and I have enjoyed working with all of you, and our project could not have been done without your help. We also want to thank all of you for sending us great emails, cards, pictures, slides, and other thoughtful items. We definitely appreciate all this correspondence. Please feel free to keep in touch and we will do our best to respond. Hopefully we'll see you again in the field.


Lee Dyer, gusanero,


Volunteer Tasks and Accomplishments

   In our 9th year of funding by Earthwatch, we were fortunate to have the help of 30 volunteers. These volunteers helped us bring our rearing total up to approximately 1800 species of butterflies and moths (26,000 individuals) and over 350 species of parasitoids. The four teams participated in all aspects of our Forest Caterpillars project. Team members searched for and collected caterpillars, noted possible morphological or behavioral characters, and took care of the larvae. At La Selva and Tirimbina, they also assisted with experiments on the understory pepper plants, Piper spp. and helped with encapsulation experiments.

   The four teams logged over 1400 total person hours in the field, searching for and recording data on caterpillars and working on related experiments. At La Selva and Tirimbina, they found over 1900 caterpillars belonging to 55 butterfly and moth species in 21 families; at least 9 of those were new species. From these caterpillars they reared over 20 species of parasitoid wasps and flies. At the Southwest Research Station, volunteers collected 210 individual caterpillars for a total of 45 species in 16 families. At least 8 species of parasitoids were reared. The teams in Ecuador contributed to our new NSF funded biotic survey and inventory of the eastern slope of the Andes, collecting 1400 caterpillars, including 75 species and 18 families, and a couple dozen new species. The site will continue to yield many new species of caterpillars and parasitoids (Figure 3). The levels of parasitism at our 3 Earthwatch sites were used in our important new finding that climatic unpredictability is associated with lower levels of parasitism.




Figure 3a. A new species in the family Geometridae. It will be years before this caterpillar receives a name (the genus may be undescribed). Tirimbina Biological Station, Costa Rica.



Figure 3b. A cryptic lycaenid caterpillar from the Southwest Research Station, Arizona. The plots and other survey work we completed at this research site allowed us to complete the analyses of trophic interactions described in this report.


Project Development  

   The data we have collected thus far at all sites support our hypotheses that the dynamics in these strikingly different habitats (Arizona, Ecuador, Costa Rica, Louisiana) are very similar, but the actors are different — species composition of the caterpillars and their parasitoids show almost zero overlap. The larvae that we studied exhibited a wide array of defenses, and we continued a focus on two specific defenses: frass-throwing and encapsulation. Several more years of data will allow us to make conclusions about how these defenses function against different types of parasitoids. For all sites, we will continue to focus on collecting new species (Figure 4), but we will also focus more on altitudinal gradients in parasitism, similar to the precipitation gradient that we’ve tested.


Figure 4. This Notodontid caterpillar, Nebulosa elicioi, was parasitized by an ichneumonid wasp, which has pupated in the old skin of the caterpillar (which is now dead). Both the moth and the specialized parasitoid were new species. You can find more information on the web page for this species:



Educational Opportunities


Educational opportunities were provided to: 

  • Local communities. We hired and trained four local naturalists and gave talks to local residents at all of the research sties.
  • Students. Seven graduate students in Dyer’s laboratory participated in the projects, either directly or by analysing data and working on papers. Eight undergraduates were also involved with the Earthwatch research. One PhD dissertation was completed with help from the Earthwatch funded work.
  • Early career scientists. Two post doctoral researchers (Stireman and Gentry) helped run Earthwatch teams.

Our Earthwatch project has united workers from Costa Rica, Ecuador, and the United States to maximize the effectiveness of caterpillar-parasitoid inventories. All of the research stations involved are centrally located near a wide variety of habitat types, including national parks and other protected areas. The research and associated educational activities enhance the educational and conservation missions of these field stations. More directly, the education and employment of local workers on the projects greatly enhance the credibility of conservation projects.




Research assistants:

Costa Rican paraecologists: Gerardo Vega, Humberto Garcia, Maylin Paniagua

Ecuadorian paraecologists: Rafael Maitio, Wilmer Simbana, Maria de los Angeles

Graduate students: Angela Smilanich, Malia Fincher, Michael Olson, Clark Pearson, Tara Massad, Genoveva Rodriguez, Kathleen Burke



Dr. John Stireman, Tulane University, Ecology and Evolutionary Biology

Dr. Grant Gentry, University of Maryland, Entomology

Dr. Craig Dodson, Mesa State College, Chemistry

Dr. Thomas Walla, Mesa State College, Biology

Dr. Daniel Janzen, University of Pennsylvania

Dr. Deborah Letourneau, University of California, Environmental Studies

Harold Greeney, Yanayacu Biological Station


Cooperating Institutions:  

Western Colorado Center for Tropical Research

Organization for Tropical Studies

Tulane University


Grants from additional funding sources: 

National Science Foundation – Ecology

National Science Foundation – Biotic Surveys and Inventories

National Geographic

Tulane University

United States Department of Energy