The Life Collection

Intimate Relations (8x4)

Air date: Dec 14, 2005

The penultimate episode focuses on the relationships between invertebrates and plants or other animals. It begins with ants and aphids: the former 'herd' the latter and protect them in return for secreted honeydew. The activities of gall-inducing insects are described, using the example of the oak tree. Many plants recruit insects to aid pollination, offering nectar for doing so, and some predators have adopted camouflage to take advantage of this, such as the crab spider. Stick insects rely on ants to hide their eggs underground for them in safety. In the Californian desert, the blister beetle's larvae congregate on a stem and, by releasing a pheromone, attract a male digger bee on the lookout for a female. They climb aboard their visitor and eventually transfer to its mate, which will in turn unwittingly deposit them in its nest — providing sustenance. An orchard spider is shown enduring a parasitic wasp grub, which injects its host with a hormone that deranges it and halts the spinning of webs. The grub then sucks the liquid from the spider's body and uses the remaining silk to form its cocoon. Fairy wasps are so small that they can lay their eggs inside those of water beetles — and can even mate while inside them. The tiger beetle larva ambushes ants by plugging its burrow with its head and pouncing. However, this doesn't work with Methocha, an ant-like wasp, which avoids the jaws of the beetle larva, paralyses it with a sting, and lays its eggs on the host. After dragging the paralysed larva deeper into the burrow, the entrance is carefully plugged and concealed.