frogwoman
Let them eat newts
Not sure if that's strictly true - other animals such as lions can be seen to play with each other in the wild - surely that's a leisure activity? Not sure about insects however. We're the only species that has developed it to such a huge degree, though.
And as Callie said maybe the lack of a consciousness could be an evolutionary advantage. For example, I can't think that an aphid which was aware of its surroundings and of its probable eventual fate - killed by a large number of different organisms in a variety of progressively nastier ways - would be incredibly happy. It would be enough to make the aphid suicidally depressed. I don't know if aphids can be depressed but if they could it probably wouldn't do much for their survival ...
"I can't face going out and eating leaves today ... what a terrible world I'm bringing my children into ... there's no point in my life, all I do is eat and produce more aphids ... I'm such a failure and any minute now I'm going to be eaten ... oh shit ..."
And as Callie said maybe the lack of a consciousness could be an evolutionary advantage. For example, I can't think that an aphid which was aware of its surroundings and of its probable eventual fate - killed by a large number of different organisms in a variety of progressively nastier ways - would be incredibly happy. It would be enough to make the aphid suicidally depressed. I don't know if aphids can be depressed but if they could it probably wouldn't do much for their survival ...
"I can't face going out and eating leaves today ... what a terrible world I'm bringing my children into ... there's no point in my life, all I do is eat and produce more aphids ... I'm such a failure and any minute now I'm going to be eaten ... oh shit ..."
ladybirds, grasshoppers, butterflies, beetles etc are something different, i feel quite upset when I see a dead ladybird or a butterfly (unless I've killed it on purpose like one of the harlequin ladybirds, but even then I still feel pretty guilty). 
