Thorn Bug

The thorn bug is a small treehopper native to the tropical and subtropical Americas, ranging from the southern United States through Central America and parts of South America and the Caribbean, and it has also become established in other warm regions where suitable host trees grow. It belongs to the family Membracidae, a large group of Hemiptera known for the dramatically enlarged, often bizarrely shaped pronotum, the plate covering the thorax, which in this species is drawn out into a sharp, laterally flattened spine resembling a thorn.

This exaggerated body shape is a striking example of camouflage, allowing individuals, and especially clusters of thorn bugs lined up along a stem, to closely mimic a row of woody thorns to the eye of a potential predator. Colours range from green to orange, red, or brown depending on age, and nymphs and adults are commonly found together in dense groups feeding on the same host plant.

Thorn bugs feed on plant sap and are frequently attended by ants, which protect them from predators in exchange for the sugary honeydew the treehoppers excrete as a by-product of feeding, an example of a mutualistic relationship common among sap-feeding Hemiptera.

• Small, wedge-shaped body with a greatly enlarged pronotum extended backward and upward into a sharp, laterally compressed thorn-like spine
• Colouring varies with age and can be green, yellow, orange, red, or brown, often with darker mottling
• Found in dense clusters of nymphs and adults lined up along a single branch or stem, enhancing the thorn-mimicking effect
• Piercing-sucking mouthparts typical of true bugs, used to feed on plant sap rather than to bite
• Nymphs are smaller and often more brightly coloured than adults, lacking the fully developed thorn shape until later instars
• Distinguished from true plant thorns by careful inspection revealing legs, antennae, and slight movement when disturbed

Thorn bugs are found on the branches and young stems of a variety of trees and shrubs, particularly members of the legume family such as mimosa, acacia, and related species, in warm subtropical and tropical climates. Their native range extends from the southern United States, including Florida and Texas, south through Mexico, Central America, and into parts of South America and the Caribbean. They are active year-round in frost-free climates, with populations often building up on host trees during the warmer growing season.

Thorn bugs feed in aggregations of nymphs and adults on the stems of host plants, inserting their needle-like mouthparts into plant tissue to feed on sap, which can occasionally stress ornamental or garden host plants when populations are dense. Feeding produces excess sugary honeydew, which is commonly collected by ants that tend the thorn bugs in a mutualistic relationship, gaining a food source while providing the treehoppers some protection from predators and parasites. Female thorn bugs also show a degree of maternal care, sometimes remaining near their egg masses and offspring, an unusual trait among true bugs. The thorn-like pronotum serves primarily as camouflage against visually hunting predators such as birds, allowing groups of thorn bugs to blend in with the actual thorns and buds of the host plant.

Females lay eggs in slits cut into the bark or stems of the host plant using a saw-like ovipositor, sometimes covering the egg mass with a frothy secretion for protection. Nymphs hatch and feed in groups on the same stem, passing through several instars with increasingly developed pronotal spines, in an incomplete metamorphosis without a pupal stage. Development from egg to adult typically takes a few weeks to a couple of months depending on temperature, and in the warm climates thorn bugs inhabit, multiple overlapping generations can occur throughout the year. Adults continue to feed and reproduce on the same or nearby host plants, often remaining in loose aggregations with nymphs of various stages.