|Dorsal surface of the 7-spot ladybird Coccinella 7-punctata|
|Ventral surface of the 7-spot ladybird Coccinella 7-punctata|
1. Epipleuron - the folded-under edge of the elyton which fits against the body.
2. Prosternum - the front section of the thorax (analagous to the sternum or breastbone in humans), which has a small keel running front to back (here a greyish line).
3. Mesosternum - the middle section of the thorax.
4. Metasternum - the rear section of the thorax.
5. The front section of the abdomen - you can see the curved join against the metasternum.
6. The 6th (and rearmost) abdominal segment. Ladybirds can be difficult to sex, but the shapes of these segments can be useful and there is more detail in Randall et al. (1992).
You will see the prefices pro-, meso- and meta- used elsewhere to mean 'front', 'middle' and 'rear' e.g. 'profemur' for the femur of the front leg. The plates have elastic membranes between them - the abdomen is particularly flexible in males as they need to curl it beneath in order to mate, and this affect the shape of the abdominal segments and membranes, leading to subtle differences that can be used to tell males and females apart.
That's all for now (maybe I'll write an intro to beetle appendages some time) - if you want to know more about ladybirds, especially from a UK perspective, have a look at the further reading list below, and why not get involved in the UK Ladybird Survey - new volunteers always welcome!
Randall, K., Majerus, M.E.N., & Forge, H. (1992). Characteristics for sex determination in British Ladybirds (Coleoptera: Coccinellidae). The Entomologist 111: 109–122.
Brown, P., Roy, H., Comont, R. & Poland, R. (2012). Guide to the ladybird larvae of the British Isles. FSC, Preston Montford. A fold-out laminated sheet perfect for beginners.
Majerus, M.E.N. (1994). Ladybirds. HarperCollins, London. A classic - part of the New Naturalist series.
Majerus, M., Roy, H., Brown, P. & Ware, R. (2006). Guide to Ladybirds of the British Isles. FSC, Preston Montford. A fold-out laminated sheet perfect for beginners.
Roy, H., Brown, P., Comont, R.F., Poland, R. & Sloggett, J.J. (2013). Ladybirds (2nd ed.). Pelagic, Exeter. Much updated from the 1989 edition (which of course didn't have the Harlequin which wasn't in the UK then), an excellent little book with detailed keys to species, including the 'micro-ladybirds'.
Roy, H., Brown, P., Frost, R. & Poland, R. (2011). Ladybirds (Coccinellidae) of Britain and Ireland. FSC, Shrewsbury. Details of all species including maps, identification features, ecology and so on.