Red milkweed locust

Phymateus morbillosus

Red milkweed locust - Boca de Camarones, Guajira, Colombia

Quick Facts

Endemic
  • Scientific Name: Phymateus morbillosus
  • Spanish Name: Langosta roja de los algodoncillos
  • Family: Pyrgomorphidae
  • Known Nicknames: Common milkweed locust, Gaudy grasshopper, Stinksprinkaan
  • Average Length: 6–8 cm / 2.4–3.1 in
  • Average Weight: 5–10 g / 0.18–0.35 oz
  • Wingspan: 10–13 cm / 4.0–5.1 in
  • Key Feature: Vibrant red and black aposematic coloration with a warty, granular thorax
  • Primary Diet: Herbivore (Polyphagous, specializing on toxic Asclepiadaceae)
  • Range: Southern Africa (South Africa, Namibia, Botswana, and Zimbabwe)
  • Habitat: Semi-arid shrublands, savannas, and Karoo biomes
  • Social Structure: Highly gregarious as nymphs, largely solitary or loosely communal as adults
  • Nesting/Breeding: Underground (egg pods deposited in soil)
  • Conservation Status: Not Evaluated (NE)
  • Population Trend: Stable

The Red milkweed locust (*Phymateus morbillosus*), native to Southern Africa, is a visually stunning yet formidable insect renowned for its large size and vibrant aposematic coloration, which serves as a bold warning to potential predators. Reaching lengths of up to ten centimeters, this grasshopper features a rugged, tubercle-covered thorax and a striking palette of deep greens or blues contrasted by brilliant flashes of red, orange, and yellow on its wings and body. Its most remarkable adaptation is a potent chemical defense mechanism: when threatened, it exudes a noxious, foul-smelling foam from its thoracic joints, derived from the toxic milkweed plants that constitute its primary diet. This combination of "armor," brilliant warning signals, and chemical weaponry allows the slow-moving locust to thrive openly in its environment, as few predators are willing to risk a toxic encounter with such a well-defended marvel of nature.

Fun Facts

These insects are masters of chemical warfare, sequestering toxic cardiac glycosides from their diet to become lethal to most predators. When threatened, they discharge a noxious, foul-smelling foam from their thoracic joints, creating a bubbling deterrent that is as unpleasant as it is effective. They also perform dramatic deimatic displays, suddenly flashing vivid hindwings and emitting a raspy hiss to startle attackers. Because they are so heavily armed with toxins, they exhibit a peculiar lack of fear, often moving at a sluggish pace or refusing to hop away even when directly approached.

Habitats & Distribution

This species is native to Southern Africa, where it is widely distributed across countries such as South Africa, Namibia, Botswana, and Zimbabwe. It thrives primarily in semi-arid regions and temperate zones that support the growth of its host plants, maintaining a consistent presence throughout both inland and coastal provinces within its geographical range. Its habitat consists mainly of open scrublands, savannas, and grasslands where milkweed and other toxic vegetation are abundant. These locusts are also frequently encountered in disturbed environments, including rural gardens and the outskirts of agricultural land, provided there is sufficient low-lying flora for feeding and breeding. They favor sunny, well-drained areas that facilitate their development and allow them to congregate near their primary food sources.

Behaviours & Reproduction

These insects exhibit a sluggish demeanor, relying on their striking aposematic coloration to signal their toxicity to potential predators. When threatened, they engage in a unique defensive display by secreting a noxious, foul-smelling foam from thoracic glands, which contains chemical compounds sequestered from their milkweed diet. Although they are often found in large, conspicuous aggregations on host plants, they do not have a complex social structure, instead gathering primarily for communal feeding and protection through collective chemical signaling. During the breeding season, mating is a slow and deliberate process where the smaller male mounts the female for an extended period. Following fertilization, the female deposits her egg pods deep into the soil, providing a stable environment for the embryos to develop. They undergo incomplete metamorphosis, with nymphs emerging as wingless versions of the adults that already possess the ability to produce toxic secretions. This early onset of chemical defense is a critical survival strategy, allowing the vulnerable young to deter predators while they forage in exposed environments.

Diet

The Red milkweed locust is a polyphagous herbivore with a specialized preference for toxic plants, particularly those within the milkweed (Apocynaceae) and nightshade (Solanaceae) families. A fascinating characteristic of its diet is the sequestration of cardiac glycosides from these host plants; by consuming these chemicals, the locust stores the toxins within its own body to become highly unpalatable and poisonous to potential predators. This chemical defense is advertised through its vibrant aposematic coloration, signaling to birds and other animals that it is a dangerous meal. While they are capable of feeding on a wide range of vegetation, including garden plants and certain crops, their physiological adaptation to process and utilize plant toxins is their most distinctive dietary trait. Furthermore, the nymphs often exhibit gregarious feeding behavior, clustering in large groups to systematically defoliate a single host plant before migrating to find new nourishment.

Colors

The Red milkweed locust displays vivid aposematic coloration, featuring a dark green or black body covered in bright red or orange tubercles. Its forewings are typically olive-green with yellow spots, while the hindwings are a brilliant crimson or pink with black patterning, used as a startle defense. This high-contrast palette warns predators of the locust's toxicity, which is sequestered from the poisonous milkweed it consumes.