Niche construction in insects

At first sight, the behaviour sequences by which insects construct their burrows appear to be intelligent. On closer inspection, they turn out to be surprisingly rigid, showing that they cannot be governed by mental states. Carruthers (2004) describes and discusses one such case.

... [C]onsider the Australian digger wasp, that builds an elaborate tower-and-bell structure over the entrance of the burrow in which she lays her eggs... (The purpose of the structure is to prevent a smaller species of parasitic wasp from laying her eggs in the same burrow. The bell is of such a size and hung at such an angle, and worked so smooth on the inside, that the smaller wasp cannot either reach far enough in, or gain enough purchase, to enter.) She builds the tower three of her own body-lengths high. If the tower is progressively buried while she builds, she will keep on building. But once she has finished the tower and started on the bell, the tower can be buried without her noticing - with disastrous results, since the bell will then be half on the ground, and consequently quite useless. Similarly, if a small hole is drilled in the neck of the tower, she seems to lack the resources to cope with a minor repair. Instead she builds another tower and bell structure, constructed on top of the hole...

The digger wasp would seem to have an innately represented series of nested behavioral sub-routines, with the whole sequence being triggered by its own bodily state (pregnancy). Each sub-routine is guided by perceptual input, and is finished by a simple stopping-rule. But once any given stage is completed, there is no going back to make corrections or repairs. The wasp appears to have no conception of the overall goal of the sequence, nor any beliefs about the respective contributions made by the different elements. If this were the full extent of the flexibility of insect behaviors, then there would be no warrant for believing that insects have minds at all.

Carruthers argues that even though many forms of insect behaviour are caused by something triggering a fixed action sequence of perceptually guided activity, it doesn't follow that all insect behaviour can be accounted for in this way. Even individuals with minds exhibit such behaviour sequences (e.g. sneezing and coughing, which involve fixed movements of the mouth and tongue to expel noxious substances from the nose or mouth). The behavioural rigidity of certain spects of insects' lives does not entail that they lack minds.

The case of the digger wasp is troubling, however. Whereas sneezing is a reaction to an irritant in the nose, burrow construction appears to a naive observer to be a carefully controlled sequence of actions, with fine-tuned motor movements. What makes it any less mentalistic than operant behaviour or navigation? The answer, I believe, is that the wasp's behaviour is not guided by learned map-like representations, so it cannot be said to have any beliefs about the construction of its nest. As such, it does not provide a counter-instance to the account of beliefs which I have defended.