Common darter

I made up my mind that today's blip would be a ladybird. I haven't seen many this summer, but I was sure there would be plenty if I rummaged about in the foliage. There were none to be found. I then realised that there were no Alder beetles either, and there are usually tons of them about. Luckily this obliging dragon posed for me so I settled for that. Alder beetles were everywhere last summer. Is there an explanation for the lack of insects?