No doubt you have seen them around this spring – those brightly coloured grasshoppers in gaudy colours of black and red, known as “Koppie Foam Grasshoppers”. You were probably hesitant to pick one up because you know instinctively that brightly coloured insects are to be avoided. You would be right to be cautious. Such aposematic (warning) colours usually tell would-be predators to “beware; I’m toxic”.
The Koppie Foam Grasshopper (Dictyophorus spumans) is a southern African insect. Spumans means foam. It is also called the ‘Rooibaadjie’ (Red Jacket) or the Foaming Grasshopper.
Koppie Foam. Photo credit: Phillipskop Mountain Reserve
The Koppie Foam Grasshopper is a local example of an insect that assimilates toxins from the plants that it eats. Its main diet consists of the poisonous Milkweed family, although other species of plants like arum lilies are also included. As they feed on the plants, the toxins they ingest are bio-accumulated in the insects’ body tissues.
When attacked by a predator, the Koppie Foam releases bubbles of toxic foam from thoracic glands just behind its head, which contain the bio-accumulated toxins from its food plants. It smells awful, tastes awful, and is poisonous. No self-respecting predator will attempt a second bite. Predators will remember that the grasshopper’s bright colours indicate that it is noxious tasting – even a potentially lethal meal.
Another well-known example is the caterpillar of the garden Acraea butterfly that consumes the poisonous leaves of the wild peach (Kiggelaria africana), rendering it toxic to most predators. The adult butterfly is bright orange with black markings, like the Monarch butterfly, which also feeds on toxic milkweeds.
Like most other grasshopper species, the male Koppie Foam has a nuptial song to attract the female, “fiddling” on striations on the enlarged back legs.
After mating, the female lays her eggs on a milkweed plant. The eggs develop during the driest part of the year. They hatch into miniature grasshoppers called nymphs. The metamorphosis is incomplete in that there are no larval or pupal stages – only nymphs that moult several times, resulting in different developmental stages called instars. Each instar is more toxic as it consumes more milkweed and has slightly more developed wings, though adult wings are still underdeveloped. These grasshoppers are, therefore, hoppers rather than flyers.
The warning aposematic colours in the Koppie Foam are produced by accumulated pigments – black melanin and red pterins.
Gomphocarpus physocarpus is an example of indigenous milkweed (also called balloon milkweed, hairy balls, ‘balmelkbossie’, or ‘balbossie’). It has striking yellowish, ball-like fruits and is an excellent plant to attract butterflies or foam hoppers to your garden. However, it is poisonous if ingested, so keep it away from small children.
Oleander (Nerium oleander) is a popular exotic milkweed grown on local road verges. It is also poisonous.White, pink or red five-lobed flowers grow in clusters year-round, peaking during the summer. The fruit is a long narrow pair of follicles, which splits open at maturity to release numerous downy seeds.
Photo right: Hairy balls: Sanbi
Photo left: Oleander: Wikipedia
So next time you spot a Koppie foam, try to identify the toxic milkweed host the nymphs were munching.