Don't insects only behave on an instinctual level?
Many insects do behave on only an instinctual level. However,
there are also insects which exhibit learned behavior. This is
especially true of social insects such as bees. For example, bees
must learn and remember the location of food, and communicate
this to the other bees in the hive - and this example is rather
simple compared to some of the more complex tasks which bees do,
such as the democratic process through which a group of bees
selects a location for a new hive.
To find a location for a hive, many different scouts go out searching. When they return, they communicate to the other bees the location and desirability of the site which they found. The scouts then go out again and investigate a location which other bees had indicated were desirable. At this point, each scout decides whether or not this new location is preferable to the one which she herself found. When she returns back, she will communicate this to the rest of the hive. This process repeats itself, and each bee will continue to change her allegiance from one potential site to another. Eventually, certain sites will become much more popular among the bees than any of the others. The greater the number of bees which prefer a particular location, the more likely the scouts are to investigate this location and judge for themselves. In this way, the hive eventually reaches a consensus, and selects a location for their new home.
Some people will, no doubt, accuse me of using anthropomorphizing terminology in describing this process, and I am certainly guilty of this. However, it would be much more difficult to describe this process if I was not allowed to use phrases referring to what the bees "believe" or "decide".
In any case, what this story demonstrates is that there is more to insect behavior than just instinct. Instinctual behavior consists of repeating the same motions regardless of past experience. However, these bees clearly do take into account what they remember from their previous scouting missions, and they make complex decisions.
It is interesting to note that in order for this process of consensus to work, each bee has to be willing to objectively decide on the desirability of a site, regardless of whether or not this is a site which she herself found. If humans were to try to repeat this process, humans would have difficulty exhibiting such impartiality. Unfortunately, human nature is such that we tend to prefer the option which we ourselves found, regardless of whether or not it is the best one.
Follow up questions:
Do you include insects in your animal rights philosophy?
What do you do when a colony of insects infests your home?
Do you view the killing of an insect as the moral equivalent of killing a bird or mammal?
How do you know that plants can not feel pain?