The Large Blue Butterfly – A close-up on insect behaviour

The Large Blue Butterfly

A BBC TV documentary series, “Life in the undergrowth”, used advanced camera and sound technology to obtain spectacular new insights into insect behaviour. Among the many insects featured was the large blue butterfly. This has long been known to have an intimate relationship with certain species of ants. The life cycle of the butterflies is as follows:

The adult butterflies are on the wing in July, when mating occurs.

The females lay their eggs in the flowers of the marsh gentian. The caterpillar hatches through the base of the egg into the flower, where it spends two to three weeks feeding.

It then chews a hole in the flower, lets itself down to the ground on a silken thread and waits.

When a red ant finds the caterpillar, it will pick it up and take it back to its nest.

Once inside the ants’ nest, the caterpillar will be fed by worker ants and will stay through the winter and spring. During this time it grows to about twelve millimetres in length.

In early summer the caterpillar turns into a pupa or chrysalis, still inside the ants’ nest. The adult butterfly emerges about a month later and leaves the nest quickly to avoid being killed by the ants.



Ant_large_blue_butterfly.jpgThe use of highly sensitive electronic cameras allowed this to be filmed for the first time without the need for strong lights, which would have inhibited the insects’ behaviour. But even more remarkable is that ultra-sensitive microphones have made it possible to hear the insects as well. It was known that the caterpillars emit chemical signals called pheromones to imitate those of the ants, but now it has been possible to detect the clicking noises made by the caterpillar, which also imitate the ants’ own communications and fool them into caring for the interloper. Playing back a recording of these noises to the ants caused them to react by tapping the microphones with their antennae.  However, the large blue butterfly also has an enemy, a rare parasitic ichneumon wasp. Unlike the ants, it seems to know that an impostor is present and enters the nest to find the caterpillar.  It also emits a pheromone, which repels the ants and causes them to attack one another. In the confusion the wasp lays its egg in the body of the caterpillar before escaping. Subsequently the wasp grub eats the caterpillar from the inside and emerges from the chrysalis in its place.


Scientists now suspect that the wasp detects the presence of the caterpillar in an ants’ nest by the very sounds which it emits to deceive the ants. One is forced to speculate how many millions of years of experimentation in the production of complex chemicals and sound systems by these insects would be necessary for them to evolve these amazing systems essential to their reproduction, and how they managed to survive until they were perfected! Surely random mutations are wholly inadequate to explain the origin of such extraordinary behaviours. Rather, the hand of the Creator Who made “every thing that creepeth upon the earth after his kind” (Gen. 1:25) can clearly be discerned.

Acknowledgementa:“BBC listens in to insect chatter”, BBC On-line News, Science section,23 Nov. 2005.