#GBB13 - The 7-spot ladybird

This post is the first in a series covering the ID of a selection of species which are likely to be in and around everyone's gardens, parks, etc, created for the 2013 Garden Bioblitz (details at http://www.naturewatched.org/gbb.html - everyone join in!)

The 7-spot ladybird, Coccinella septempunctata, is the archetypal ladybird. Featured in toys, games and company logos, this is one of the very few insect species with a positive public image - in fact, it's nicknamed 'the gardener's friend' for its habit of devouring pest insects such as aphids.


An adult 7-spot ladybird, sunbathing to warm up

The adults are amongst the easiest insects to identify - big (5-8mm long) and bright orange, they make no effort to hide (their bright colours are a warning to predators of their foul taste), and they only come in one colour form, unlike species such as the 2-spot or Harlequin ladybirds (the snowflakes of the insect world, with no two individuals alike).

99.9% of the 7-spots you'll ever see will look almost exactly like the one pictured above - the wing cases (elytra) a bright orange/red, with a pyramid of three roundish black spots on each, and a 7th stretched across both elytra at the front, just behind the black-and-white head and thorax. Occasionally specimens miss spots, or have tiny extra ones, but in general, the picture is what they'll look like.

As a double-check, the 7-spot is one of the largest ladybirds in Britain - most of our 47 species are less than 5mm long. The only species which can look similar, and is a similar size, is the Harlequin (Harmonia axyridis), which can sometimes have very few spots, but the orange colour form of the Harlequin always has a black 'M' on the thorax, which is never present in the 7-spot.

Definitely not a 7-spot ladybird. The spotless form of the Harlequin ladybird - note the 'M' marking

Ladybirds, like most insects, have the 4-stage life cycle familiar from butterflies - egg, larva, pupa, adult. In butterflies and moths the stages can have different names - caterpillar for the larva and chrysalis for the pupa, for example - but with ladybirds, it's just egg, larva, pupa, adult.  Although not as easy as the adult, it's still entirely possible to successfully identify pupae and fully-grown larvae of the 7-spot.

Pupa of a 7-spot ladybird

A lot of people will have seen a ladybird pupa without realising what the strange, blob-like creature on the leaf actually was, and it's true, they do look a bit odd - especially when they feel threatened and rear up and down like a globular hinge! Only found in the vicinity of aphids, 7-spot pupae are rounded, orange-and-black, and big enough to fit an adult ladybird inside them (again, much larger than most of the other ladybird species), and with the shed skin of the larva at the back end, where it's attached to the leaf. The shed skin is an important feature for distinguishing 7-spot pupae from Harlequins, which are brighter orange and have a very spiky shed larval skin.

Not a 7-spot. A Harlequin ladybird pupa, note the brighter orange and obvious spines on the shed larval skin

The combination of size and lack of spines is a good pointer for the larvae, too. Again, they're big, and covered in warts (not spines), and they have a couple of orange flashes on either side, each made up of two warts, one on top of the other. There are a few fairly similar species, but none of them have the combination of large size and the 4 orange patches.  They have a voracious appetite for aphids, and you won't find them far from an aphid colony (or underneath one).


Two views of 7-spot ladybird larvae

Any ladybirds you see should be recorded at the UK Ladybird Survey website (http://www.ladybird-survey.org/), which is also well worth looking at for the other species, and for lots more information besides.  There are also plenty of ladybird photos on the web - my Flickr sets are below:

Adult ladybirds - http://www.flickr.com/photos/rcomont/sets/72157623774877905/

Pupae - http://www.flickr.com/photos/rcomont/sets/72157626283897399/

Larvae - http://www.flickr.com/photos/rcomont/sets/72157626283897399/

If you prefer paper, the Field Studies Council also publish ID charts for the ID of adult (http://www.field-studies-council.org/publications/pubs/guide-to-ladybirds-of-the-british-isles.aspx) and larval ladybirds (http://www.field-studies-council.org/publications/pubs/ladybird-larvae.aspx)

And of course, don't forget to join in with the Garden Bioblitz on the 1st/2nd June 2013! http://www.naturewatched.org/gbb.html for more details

Aliens vs Invasives

Over the last couple of days,a couple of people on Twitter have flagged up a Comment Is Free article on alien species (http://www.guardian.co.uk/commentisfree/2013/feb/23/alien-species-british-countryside-kneejerk-nature?CMP=twt_gu).  It's not a bad article (although as ever, don't bother reading the comments), but it manages to confuse & combine alien with invasive and effectively ends up arguing strongly for the status quo.

Alien species are not necessarily invasive. The two terms are often heard - often used - together, but in fact, the two are very different.  The official definition of an alien species (from the IUCN via the Convention on Biological Diversity, CBD: http://www.cbd.int/invasive/terms.shtml) is 'a species, subspecies, or lower taxon occurring outside of its natural range (past or present) and dispersal potential (i.e. outside the range it occupies naturally or could not occupy without direct or indirect introduction or care by humans) and includes any part, gametes or propagule of such species that might survive and subsequently reproduce' - basically, it's a species which people have moved to a new area.  

A recent review of the non-nativeness of the British countryside (overall, about 0.5%: data at http://www.brc.ac.uk/downloads/English%20Nature%20Non-native%20Audit%20report%20662.xls)  found that more than 2,700 alien species are at large in Britain, from Neolithic introductions such as the Large Tabby moth (Aglossa pinguinalis) to very recent arrivals like the Demon shrimp (Dikerogammarus haemobaphes).  A study on plants in Britain (Williamson & Fitter, 1996) found that, of every 100 alien species introduced to a new area, only 10 will establish wild populations, and only 1 will go on to become invasive.  In this context, 'invasive' has a strict definition, again from the CBD: a species which 'is an agent of change, and threatens native biological diversity'.  

This is the crux of the matter. An alien species may be invasive - for instance Himalayan Balsam (Impatiens glandulifera), Japanese Knotweed (Fallopia japonica), and the Harlequin ladybird (Harmonia axyridis), but so can native species. A decade ago now, I worked for the RSPB at their Aylesbeare Common reserve, a heathland site in East Devon. We spent a huge proportion of our time chopping down and otherwise killing plants which were invasive on the heathland - all of them natives, mainly Silver Birch (Betula pendula), Bracken (Pteridium aquilinum), and Bramble (Rubus fruticosus agg).  Aliens, like the pine trees scattered across the heathland, we generally left alone - they weren't spreading, so weren't invasive, so weren't a problem.

Some alien species can go beyond this, and become integral to an ecosystem. The rabbits (Oryctolagus cuniculus), mentioned in the CIF article as a long-established alien species, are crucial to the maintenance of chalk downland, and the 1950s/60s outbreak of myxomatosis in rabbit populations contributed significantly to the extinction of the Large Blue butterfly (Maculinea arion) and the near-extinction of at least three more butterfly species.

Of course, some aliens are disruptive, and there's no good way of predicting which species will establish, and which will displace or feed on natives, becoming problematic invasives. That's why border controls are strict: they're based on the precautionary principle.  We can't tell which species will cause havoc when they arrive, and it's virtually impossible to eradicate a species once it's established, so the best bet is to prevent arrival in the first place.

Some of the most notorious alien species are invasives.  The Harlequin ladybird has been linked to significant declines in native ladybirds (Roy et al., 2012), and the effects of Rhododendron & Japanese Knotweed are well known, but the vast majority of alien species fall between these two extremes.  These species lead lives of quiet obscurity with few, if any, effects on native ecosystems, like the Bryony ladybird (Henosepilachna argus) in Surrey or the Yellow-tailed Scorpions (Euscorpius flavicaudis) in Sheerness.  Consequently there's no control measures for them - they may be aliens, but they come in peace.

The flexible approach - taking each case on its merits - is presented as the big message at the end of the CIF article. But it's already common practice with alien species, in Britain and far beyond. The mere fact of a species' origin is, in practical terms, essentially immaterial: what's important is the effect it has on native ecosystems, adapted to the local area and each other.  


Refs:

Roy, H.E., Adriaens, T., Isaac, N.J.B., Kenis, M., Onkelinx, T., San Martin, G., Brown, P.M.J., Hautier, L., Poland, R.L., Roy, D.B., Comont, R., Eschen, R., Frost, R., Zindel, R., Van Vlaenderen, J., Nedvěd, O., Ravn, H.P., Grégoire, J.-C., de Biseau, J.-C. & Maes, D. (2012b) Invasive alien predator causes rapid declines of native European ladybirds. Diversity and Distributions, 18, 717-725.

Williamson, M. & Fitter, A. (1996) The Varying Success of Invaders. Ecology, 77, 1661-1666.