Answer: There are different species of ladybugs (Hippodamia), so this may explain part of the difference in coloring you are noticing. Also, there can be color differences within a species and between male and female ladybugs. Here is a link to an article that shows some photos with tremendous variation in the coloring. You may need to cut and paste teh complete url into your browser to make it work correctly.
Ladybugs (their larvae in particular) assist in controlling pest insects such as aphids so they are very useful. In my experience the ladybugs tend to appear on a plant that is suffering an aphid infestation and then will move on when the aphids are gone.
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