I think that they've arrived after your apples have already been eaten, probably by wasps, because as far as I know ladybirds only feed on aphids!
I'm sure not if they are harlequins, and even if they are I'd leave them be.
This site may be of interest - http://www.ladybird-survey.org/ladybirds.aspx
Yes I am amazed but they appear to be eating......although I probably need to get an eye-glass to look closely. Interesting also that they seem to be keeping the wasps at bay. Just loved the web-site.....