Masters of disguise: the crypsis behaviour

Crypsis, the act of disguising oneself as one’s background or another unimportant object, is used in the insect world largely for survival - usually in order to avoid being eaten. PhD student James O’Hanlon of Macquarie University is researching how crypsis and mimicry are used as a signalling strategy, one by which an individual attracts the attention of other animals.

According to John Endler of the University of Utah, crypsis is when an animal resembles its background, such as the plant it lives on, whereas mimicry is when an animal resembles another organism.

O’Hanlon is studying how the Malaysian Orchid Mantis (Hymenopus coronatus) uses crypsis to imitate the orchid flower in order to lure prey, with the shape, size and colour of the mantis and its limbs resembling orchid petals. This similarity appears to trick insects into foraging near the mantis, seeking out what is non-existent nectar and then falling prey to the mantis.

The Malaysian Orchid Mantis.

O’Hanlon is also investigating how stick and leaf insects’ (phasmids) eggs mimic the appearance of some tree seeds. These eggs have a capitulum which seems to attract some species of ant. These ants have been observed to take both seeds and eggs into their nest, with the seeds collected as a food source and eaten by the colony. The curious thing is that the eggs are ignored once underground. The ants no longer care for it as a food item or anything else.

Studies are being carried out to determine why this is. There is no clearly observable benefit for an insect’s egg to resemble a tree seed or be collected by ants; however, once underground the eggs are no longer exposed to predators or environmental changes, ie, temperature and weather.

Behavioural experiments are being run to see whether the ants are attracted to the capitulum or the egg itself. This includes experiments where eggs are placed in their habitat, as well as foam balls with a capitulum attached, and eggs with the capitulum removed. Current observations show that in general, ants tend to be attracted to the capitulum more than the eggs, suggesting that it is the capitulum which is important to the ant. The chemical composition of the capitulum and why ants are attracted to it are currently being investigated by O’Hanlon.

The crypsis behaviour used by the orchid mantis and phasmids is relevant to these species’ survival, as well as how and why they evolved; this is what O’Hanlon aims to discover.

With thanks to James O’Hanlon.