Focusing on the familiar VI: ladybirds part 4

It's a year and a half since I started my occasional series looking in a little more detail at familiar species. In that post I looked at the 'typical' 7-spot ladybird Coccinella 7-punctata, including the yellow colour it shows when newly emerged as an adult, and compared it with the Harlequin ladybird Harmonia axyridis. This time, I decided to go back to the 7-spot and look in a little more detail at its external anatomy.

Dorsal surface of the 7-spot ladybird Coccinella 7-punctata

The dorsal surface is fairly straightforward and is what we usually see - the pair of wing cases (elytra) showing the familiar orange-red colour with seven black spot, the black and white pronotum in front of this, covering the thorax, and the head which is mostly hidden, although you can see the antennae protruding here. The ventral surface is a little more complex, and it's useful to become familiar with the standard terminology.

Ventral surface of the 7-spot ladybird Coccinella 7-punctata

I have ignored the appendages (legs, antennae and mouthparts) on this occasion but have numbered some of the other features that may be less familiar as they illustrate how the plates fit together to for the exoskeleton:

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!


Reference

Randall, K., Majerus, M.E.N., & Forge, H. (1992). Characteristics for sex determination in British Ladybirds (Coleoptera: Coccinellidae). The Entomologist 111: 109–122.

Further reading

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.