Georgetown College. Georgetown University.

Tucked away in a quaint, historic corner of campus by the Yates Field House, Dr. Martha Weiss’ Ecology Laboratory is buzzing with insects and activity. She and her students are busy making breakthrough discoveries about the tiny minds of these sometimes beautiful, and other times annoying or frightening, creatures that are vital to our world’s ecosystems.

While pursuing her Ph.D. in Botany at the University of California at Berkeley, Dr. Weiss observed the blooms of common flowers changing color as they matured and asked herself, “why do flowers change color?” In nature, it is rare that change happens arbitrarily, and the answer to her question led Dr. Weiss to the rich and complicated world of plant-and-insect interactions.

Dr. Weiss’ dissertation was among the first projects to demonstrate tangibly that the changing color of flowers or floral parts serves as a mode of communication with insects that feed off of and pollinate them. She learned that the plants effectively train the pollinators to visit the more fertile, nectar-rich flowers. An insect’s more frequent visits to flowers of a particular color that bear more nectar (the younger flowers on the plant) results in a more efficient pollination for the plant, making for a mutually beneficial, efficient ecosystem driven by dynamic interaction. Through various experiments with butterflies, Weiss confirmed that while some butterflies innately prefer certain colors, they readily adapt their feeding and pollinating behaviors based on the colors of the most rewarding flowers in their environment, thus demonstrating a dynamic capacity for learning in the butterflies. “A capacity for rapid and flexible associative learning presumably allows butterflies to adjust their foraging efforts in response to floral rewards that vary over space or time.” (MRW 1997)

Dr. Weiss’ current work at Georgetown as an evolutionary ecologist focuses on the dynamic interactions of ecologically interdependent plants and insects. Many of the interactions that she and her colleagues study, specifies Dr. Weiss, are tri-trophic, meaning they are composed of three actors that rely on the relationship for nourishment. Thus, plants, herbivorous insects (such as butterflies and caterpillars), and predatory insects (such as wasps, who prey on the caterpillars), are all interdependently involved. A key element in these interactions, according to Dr. Weiss and her colleagues, is learning and memory in insects (both herbivorous and predatory), which is the focus of her and her students’ projects.

Most research on learning and memory in insects has centered around social insects, such as honeybees or ants. Solitary insects are required to be self-sufficient multi-taskers, and learning and memory skills allow them to adapt to their environments, which is vital to their optimal survival. Dr. Weiss and her students’ research is yielding new information that solitary insects, such as butterflies, caterpillars, and wasps, also have the ability to learn and remember, possibly even more so than social insects.

While extensive work has been done in Dr. Weiss’ lab regarding color and smell learning in butterflies, Maria Wadlington, an undergraduate, is conducting experiments with Monarch butterflies to determine pattern and structure learning abilities. Wadlington begins by constructing fake flowers out of cardboard cutouts with printed patterns on them, including concentric circles, radial patterns, stripes, polka dots, and a target (a single dot in the middle). She also creates flowers with lines leading either to the center or to the edge of the flower, using both flat and folded flowers. She tests both innate preferences and the butterflies’ ability to distinguish and learn certain patterns and/or leading lines. Wadlington affixes the fake flowers to Petri dishes or pipette tips, which are then selectively filled with nectar, and then she records the frequency and duration of the butterflies’ visits to each flower. So far, Wadlington has found that monarch butterflies are able to distinguish patterns in flowers, having an innate preference for flowers with a radial pattern, and are able to be trained to visit flowers with a target pattern. She has also found that they have a preference for flowers with lines leading to the center, while so far her data has not shown a differentiation of folded versus flat flowers by the butterflies.

Megan Dougherty, an undergraduate in her senior year, is studying predatory behaviors in praying mantises. She has been observing adult female mantids presented with both palatable and “dangerous” (likely to fight back) or noxious (toxic or odor-emitting) prey. Dougherty has found that mantids do indeed eat all of them, with a longer handling time for the dangerous ones, and innately leave untouched the noxious parts of their prey (for example, the wings of a monarch butterfly are toxic, and the mantids do not eat them, while they will eat wings of other kinds of butterflies).

Dougherty is also working alongside graduate student Heather Mallory, who is studying mantid learning abilities at different times in their life cycle, as well as their brain structure and their ability to learn make use of olfactory cues. Dougherty is particularly interested in the influence of environmental stimuli on the development and size of mushroom bodies in their brains. Mushroom bodies are hypothesized to be centers of learning and memory in insects, and their size has been shown to vary with environment and experience in other animals such as bees and rats.

Dougherty and Mallory have been raising mantids in both social and asocial environments, where the social ones are given extra stimuli (visual and floral cues, playdates, different and novel prey items). Dougherty and Mallory will be the first to dissect mantid brains and identify and examine their mushroom bodies, so they are treading on new territory.

There are currently three other graduate students and a post-doctoral student working in Weiss’ lab. Doug Blackiston, a graduate student, has been conducting experiments that have demonstrated the ability for manduca moths to remember something they learned as caterpillars. Divya Uma, a graduate student in Weiss’s lab, is studying predator-prey interactions between mud-dauber wasps and spiders in the wild. Uma is looking into factors affecting hunting success of these spider hunting wasps. Currently, she is testing whether three-dimensional webs built by spiders act as defensive structure to avoid wasp attacks. Daniela Rodrigues, who comes from southern Brazil, is doing post-doctoral work in the lab, building upon Weiss’ work with monarch butterfly learning and memory.

Diverse research interests abound in Weiss’ lab, making it into an even more vibrant learning community for her students. According to Uma, “Dr. Weiss is very encouraging and gives her students the opportunity to explore and study anything of their choice. Though one of the main themes of our lab is insect learning, many of us work on different systems and are asking different questions. Interacting with lab mates thus gives a holistic approach in understanding insect behavior.”

“Dr. Weiss creates a lab atmosphere which is welcoming and personal. Each student gets to work with one another, constantly learning and growing together. As an undergraduate this is vital, to have the graduate students and a post-doc readily willing to help, serving as great mentors for us as well,” adds Wadlington.

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