Looking after babies can be a time-consuming business, but it is important to give your offspring as good a start in life as possible. The mud-dauber wasp Sceliphron laetum takes great care in protecting and feeding its young - it makes a chamber out of mud, lays an egg in it, and then fills the chamber with a supply of edible spiders for its developing offspring to eat.
Researchers Mark Elgar and Matthew Jebb at the University of Melbourne in Australia took a close look at mud-dauber wasp chambers on the walls and under the floorboards of the Christensen Research Institute in Madang, Papua New Guinea, to examine what female wasps were putting into storage with their eggs.
They found that the mothers-to-be collected more than 12 different species of spider and that rather than simply filling the chamber to the brim, they stopped once a certain mass of prey had been stored. Interestingly, they packed the spiders into the mud chamber in a certain order - spiders of one genus, Gasteracantha, were never put first.
A newly hatched larva’s first meal has to be soft and easy to eat. Only when more mature can it manage to digest species such as Gasteracantha, which have tough outer layers. But because a larva consumes spiders in the order in which they were stored in the nest, careful selection and packing by a mother mud-dauber can ensure that her offspring has access to the best possible food as it grows.
(Behaviour, vol.136, pp147-59).
Background
Many wasps have found ingenious ways in which to look after their eggs - or to get others to do the job for them. They exploit a diverse range of hosts from other insects such as live caterpillars to fruits such as figs.
The parasitoid wasp Trichogramma minitum, for example, lays its eggs inside the eggs of other insects. When it finds a suitable host egg, it injects its own eggs using an ‘ovipositor’. Once in place, the eggs develop, and the young consume the ready supply of food - the host egg.