So imagine that you are a female ladybird. Because you are already four days old you feel it is really about time that you get a hold of yourself and cease to live your life in an aimless fashion. You feel that it is time to get pregnant. While wandering about on your green plant reflecting on where your life has gone you suddenly look up and see an attractive male about 2 cm ahead (which is about how far a ladybird can see). You feel really flattered when this handsome stud mounts you, but then, when he is just about to insert his thing you instinctively start to run around, kicking forcefully backwards to get him off. This stud won't give up that easily though so in spite of the rather uncomfortable ride he hangs on. You therefore switch to a different strategy. Almost to your own amazement you throw yourself of the green plant and falls towards the ground. You make your handsome stud lands first thus making him absorb the long fall. For a second the male lets go of you and you try to escape, but luckily for the male he retains his consciousness before you have been able to run more than 2 cm away in which case he would not have been able to find you.
The stud mounts again and this time you don't fight. Instead you think to yourself, this guy can copulate right after falling down an equivalent of ten floors, now that is a trait I want my ladybird offspring to have. So the romance begins, and since you are ladybirds, and since ladybirds are fond of copulating you go on for a long time. (Here is a video of two ladybirds getting it on to the tunes of Donald Crawford's "You Know I Know".)
If both the male and the female have not mated recently they will keep going for about 275 minutes, or 4.5 hours. However, if both have had sex recently and thus feel a bit tired or drowsy or satisfied, then they will limit they will stop after only 176 minutes or 3 hours.
Following not so much cuddling you depart, exhausted but happy… However, for a ladybird sex is not just joy. Because ladybirds are really really promiscuous animals they are also very often the victims of sexually transmitted diseases, in fact the ladybird has more STDs than any other insect. According to one estimate that I found, up to 90% of some populations of ladybirds can be affected, so you better use the condom (or become a ladybird nun).
Most of what you have read here is my recollection of a lecture that was given to me by Professor Mike Majerus at Cambridge University, UK. In 2004 I attended a science summer school at Fitzwillam college and there I had the great privilege of taking a course called "sex and aggression in insects" taught by this extraordinarily entertaining ladybird world authority (I would vote for him to take over after David Attenborough if he ever quits). Though I have not read his books he has written several, so if you are interested in ladybirds and evolution I am sure that the following books are probably really good references.
Melanism: Evolution in Action: In this book majerus decribes the evolutionary forces that has given rise to melanism, or skin color. I'll bet that many of the examples are on the somewhat rare black ladybirds which he talked alot about during his course.
Guide to Ladybirds of the British Isles: As the title suggests this is a short (8 pages) guide to ladybirds.