The Eastern Lubber Grasshopper (Romalea microptera) is a large, flightless insect common in the wet grasslands and scrub areas of the southeastern United States. These grasshoppers are recognizable by their distinctive, bright coloration, typically involving patterns of yellow, red, and black. This bold appearance signals toxicity to potential predators. Despite being abundant and slow-moving, the lubber is not a common meal for generalist predators because of a sophisticated defense system.
The Lubber’s Defense System
The lubber’s vibrant colors are an example of aposematism, signaling toxicity or distastefulness to predators. This visual deterrent is paired with chemical defenses, which are both sequestered from their diet and manufactured internally. Lubbers feed on various plants, including those containing noxious compounds like oleander, allowing them to absorb and store toxins such as cardiac glycosides.
The composition of these defensive chemicals varies widely depending on the grasshopper’s diet, preventing predators from developing consistent tolerance. When disturbed, the lubber deploys a two-pronged chemical attack. It may secrete a noxious, foul-smelling froth from its spiracles, which are the breathing pores on its body.
The grasshopper may also regurgitate a dark brown liquid, known as “tobacco spit,” which is a blend of recently consumed, toxic plant material. These defenses are highly effective against most vertebrate predators, including birds, lizards, and small mammals. The varying toxicity ensures that most animals quickly learn to avoid the brightly colored insect.
Specialized Avian Predators
Despite the potent defenses of the adult lubber, a few specialized avian predators have developed methods to overcome the toxicity. The most prominent is the Loggerhead Shrike, nicknamed the “butcherbird” for its unique hunting technique. This medium-sized songbird preys on adult lubbers, which are too large to be consumed whole.
The shrike dispatches the grasshopper and impales its body onto a sharp object, such as a thorn or a wire fence barb. Leaving the lubber impaled allows the toxins to degrade or dissipate, effectively “curing” the meal before consumption. This detoxification strategy is a specialized adaptation that allows the shrike to exploit this food source.
Other opportunistic birds, such as crows and kestrels, may target the grasshoppers, particularly the less toxic nymphs. These birds may consume smaller, younger lubbers or employ strategies to remove the most noxious parts before eating. The shrike is the primary example of a vertebrate predator that consistently preys on the adult form.
Other Opportunistic Eaters
Invertebrate predators target the lubber grasshopper, often focusing on its vulnerable life stages. Parasitic flies, such as certain tachinid species, lay their eggs directly on the adult lubber. The fly larvae hatch, burrow into the grasshopper, and consume it from the inside, eventually killing the host.
Younger, newly hatched nymphs are susceptible to generalist predators before they accumulate sufficient toxins from their diet. Small spiders and predatory beetles can subdue these smaller, less chemically defended nymphs. These early stages provide an opportunity for predators that would otherwise be repelled by the adult’s size and chemical defenses.
Reptiles and small insectivorous mammals, like lizards or raccoons, typically avoid the toxic adult lubber. However, they may occasionally consume a young nymph or a deceased adult if food is scarce. The eggs, laid in pods beneath the soil, are also targeted by ground-dwelling insects and rodents.