Peter Evans & Geoff Deehan, The Descent of mind: The Nature and Purpose of Intelligence, Londres, Grafton, 1990, p. 139.

There is further evidence from the efforts of some animals to manipulate their environment. Birds’ nests are perhaps the most familiar of these but there are many others examples. The larvae of caddis flie, for instance, will cover themselves with. accretions of sand, leaves and other matter It might seem that caddis flies can’t bee choosers- that they would make use of of anything that floats past. In fact, the various species display considerable discrimination in choosing their building materials. They seem to do this assessing the materials with their mouths, rejecting those that do not appeals. Again, it is easy to speculate that the caddis fly is a slave to its genes. But the list of genetic instructions that would account for this master builder’s abilities is a very long one indeed. A far simpler insight into the behaviour is to suppose that the larvae know what they are doing at some level, and that their behaviour is purposeful and directed