Leaf Insects

I’m not going to talk about how a leaf insect mimics a leaf, that would be too obvious! Instead I’m going to discuss the nature in which Spiny Leaf insects (Extatosoma tiaratum) lay their eggs and deceive ants in the process. 

A female adult spiny leaf insect (Extatosoma tiaratum) displayed on a leaf (AUSECO, 2008)

Eggs produced by leaf insects resemble seeds often from a mixture of toxic and non-toxic plants (eg. Lupins sp. and legumes respectively). A capitula like structure formed on the crown of the egg is lipid rich and a favourite food of ants. The ants carry the egg to their nests where it is protected from birds and other predators such as wasps. Once the egg has hatched, the first instar nymph stage resembles the larvae of ants (documented in Leptomyrmex ants by Key, 1970) facilitating movement from the nest to the surface without detection. This deception allows for increased survival of leaf insects eggs, where on the surface they would have been predated by birds. Shelomi (2011) found that quails (Coturnix japonica) and chickens (Gallus gallus domestica) eagerly consume the eggs produced by spiny leaf insects, but unlike most plant seeds the eggs did not survive digestion. Just one in nearly a thousand eggs remained intact after consumption by these bird species, providing strong observations that without the protection by ants in their nests spiny leaf insect eggs would not survive long enough to hatch, detrimental to the population of the species (Key, 1970; Sellick, 1997; Shelomi, 2011).

WATCH: the interaction between ants and spiny leaf insect eggs as shown by David Attenborough 

References:

Key, J. 1970. “Phasmatodea”, CsiRo (ed.) the insects of Australia. Melbourne University Press, Melbourne, Australia pp. 348-359

Sellick, J. 1997, "The range of egg capsule morphology within the phasmatodea and its relevance to the taxonomy of the order", Italian Journal of Zoology, vol. 64, no. 1, pp. 97-104.

Shelomi, M. 2011, "Phasmid Eggs Do Not Survive Digestion by Quails and Chickens", Journal of Orthoptera Research, vol. 20, no. 2, pp. 159-162.

Image:  

AUSECO, 2008.  http://www.auseco.com.au/index.asp?pagename=eco+updates+phasmids

Accessed: 10th May 2015