Ladybug, ladybug, fly away home

I bought a bag of ladybugs for our garden. We let them go at dusk, and in the morning they were hanging out for Chloe to play with. Alas, they only stuck around for another day. We weren't sure why they left, but later learned it was likely we did not have enough food for them. I guess it is good that there were not many aphids on our plants, but Chloe sure was sad that they left.