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.

Dining on smut and other corny puns

A couple of weeks ago, I wrote about the smut fungus Ustilago maydis that grows on sweetcorn. While doing that, I found out that it is edible, and in Mexico is eaten as a delicacy called 'huitlacoche'. I also mentioned that if I found some more that wasn't quite so over-mature, I'd try it. I found some, I cooked it, and I ate it. So, in a rare departure from ecology on 'the spot', here are a couple of pics of the taste test.

A cob with U. maydis growing on it, being chopped and prepared.

Bits of huitlacoche fried and ready to eat.

The outcome of the taste test was pretty favourable - unsurprisingly a kind of cross between mushroom and sweetcorn, and quite subtle. I've found another growth in our sweetcorn patch, so that will be cultivated and I'll try more next time...

Grubs within grubs within grubs

Back in the 17th century, Jonathan Swift (he of Gulliver's Travels fame) wrote:

"So nat'ralists observe, a flea
Hath smaller fleas that on him prey;
And these have smaller fleas to bite 'em.
And so proceeds Ad infinitum."

Then, in the 19th century, mathematician Augustus De Morgan updated this to the more familiar

"Great fleas have little fleas upon their backs to bite 'em,
And little fleas have lesser fleas, and so ad infinitum."

Well, this might not proceed quite ad infinitum, but there certainly can be several tiers of parasitism. One common example involves the small wasp Apanteles glomeratus (family Braconidae) which parasitises larvae of the 'cabbage' white butterflies Pieris brassicae and P. rapae. Eggs are laid into the butterfly larvae, where they hatch and develop - after about 15 to 20 days the wasp larvae emerge and the host dies. The wasps then pupate in silken cocoons next to the dead host, creating the arrangement that can be seen attached to a wide range of substrates, sometimes in very exposed situations (such as the middle of a glass patio door...), with the whole cluster attached by silk threads.

A typical arrangement of Apanteles glomeratus cocoons by the dead host larva of Pieris brassicae.

Apanteles glomeratus cocoons showing the tangle of silk threads.

I have seen  numerous examples of this arrangement over recent days, largely because following several very poor summers in the UK, Pieris spp. are some of the few butterfly species to have done well, and consequently there are many of their larvae for parasites to target. Also, as Pieris spp. are ravenous eaters of brassicas in farms and gardens, A. glomeratus is a vegetable-grower's friend. However, if I look more closely, I might find 'hyperparasites' (parasites of parasites) such as the tiny ichneumon wasp Lysibia nana which targets braconids such as A. glomeratus. Closer still and - well, I don't think anyone has investigated - but I'd expect to find microscopic protozoan, fungal or nematode parasites. Maybe I need to capture some L. nana and have a look.

If you would like more technical detail about parasitic wasps, Ronquist (1999) gives details of their phylogeny, classification and evolution (including, in Table 1, some examples of who parasitises who). In contrast, if you fancy an excellent (and silly) photo of a braconid larva, try here instead (or, as well - I like both, and Myrmecos is a fine blog looking at entomology, often ants, from a more photographic viewpoint).

Reference

Ronquist, F. (1999). Phylogeny, classification and evolution of the Cynipoidea. Zoologica Scripta 28(1-2): 139-164.

Smutty farming

Yup, an obvious pun I know, but hey... as you may know if you read this blog regularly, I am a stakeholder in a community farm - we're chemical-free and pretty wildlife-friendly, and as such use either (a) cunning or (b) many pairs of hands to deal with pests. Of course, we get a few, but they can be interesting in their own right - like yesterday when I found a single fist-sized growth of common smut fungus (Ustilago maydis) at the base of one of our sweetcorn plants.

Common smut Ustilago maydis on sweetcorn

Close-up of U. maydis showing a small growth of the sweetcorn plant.

The fungus can grow on any part of the plant, though, as here, it most commonly affects the cob/seeds which expand and become filled with spores - essentially it causes a gall. It is fairly common, and its presence this year is unsurprising as conditions have been ideal - hot, dry weather while the plants are establishing, followed by rain as they mature - exactly what has occurred. It can cause major crop losses, though our non-intensive 'hands-on' approach means that we'll simply look out for and remove any more if they appear (the standard advice is to burn or bin them, but not compost them as the spores will survive and spread).

Interestingly though, I have found out that the fungus is actually edible, particularly if relatively young (this specimen was very mature and entirely spore-filled), and in Mexico is a delicacy known as 'huitlacoche' which is eaten in a succotash, or in tacos or omelettes. Apparently it's kind of nutty-mushroomy and quite nice but not popular elsewhere as it's seen as a 'disease'/'rot' rather than food - and I must admit it doesn't look that appealing. However, if I find another, less mature one, I'm going to try it - seems a good use of a failed cob! I may report the results here...