Too much time in the gym!
I love the nature reserve at this time of the year, when new insects seem to be appearing every day. This is one I look forward to seeing in June - Oedemera nobilis or Swollen-thighed beetle. This is the male, who seems to have been spending too much time on leg muscle development at the gym. The female, sensibly, has normally shaped legs...but no doubt her head is completely turned by a male with enormous swollen thighs. Any striking feature on an insect is there either for sex or protection...simple!