Saturday, September 19, 2009

Frog spit & colour morphs: Pseudodiversity & other false ideas

Frog spit and spittlebugs are one of those childhood memories that now evoke mixed feelings. Did I really eagerly plunge finger tips into poop and plant-sap spittle and react with joy when uncovering a frothing froghopper nymph?

Well, that’s how I remember it, but now things are different. Spittlebugs (true bugs: Order Hemiptera, Family Cercopidae) or froghoppers (as the adults are called) are interesting insects for any number of reasons. One of the primary is, of course, the protective envelope of bubbles that the nymphs generate around them as they feed. That’s cool, even if you aren’t a kid, but once you know that the bug anus is intimately involved, one is apt to get a bit skittish (NB – always wash your hands after playing with spittlebugs). Adult fastidiousness aside, the most likely spittlebug one is apt to encounter is two things you don’t want in a garden bug: polyphagous and exotic. Another way to say this is ‘an alien that eats everything’.

Summer before this, we had quite the explosion of just such a spitting machine in the Home Bug Garden: Meadow Spittlebugs (Philaenus spumarius). Bellflowers, globe flowers, Queen-of-the-Prairie, goldenrod, aster, yarrow, and many other cherished garden gems had hunks of spit sitting just below the flower buds – wilting the buds and terminating the flowers. Hundreds of soapy squirts and weeks of spit and green ocher stained finger tips later, the spit population appeared undiminished. It was enough to drive a knee-jerk environmentalist to the evils of synthetic insecticides – if only such a synthetic chemical alternative were available! Alas a history of insecticide abuse, and the inability of government to favour science over fervour, has left the home gardener with little to do other than pray for parasitoids. Unfortunately, spit and parasitoids don’t seem to mix.

Not that I am entirely the innocent victim in this outbreak. I suspect the main reason for our spit-drenched garden was that I left most of my perennial plant stems standing over winter. I could claim that I did this for aesthetic reasons (winter interest), horticultural reasons (plant tops trap snow and help plants to overwinter), or just plain knee-jerk environmentalism (it is natural for plant tops to last over the winter and cutting them down would be unnatural and wrong). Truth be told, being a lazy bugger (aka ‘overworked’) conspired with all of the before to let the tops stand. Unfortunately, it is inside the stems of perennial plants that the froghopper secrete their eggs – the eggs that turn into spit and dead flowers the next Spring.

This last year I cut down and composted my perennial tops before Spring had sprung. Leaving them up most of the winter looked good and trapped snow, and cutting them down before it got warm seems to have kept the spittlebugs down to squishable levels. Other insect pests and diseases also overwinter in plant tops, so ‘better late than never’ applies here. The only downside to this approach is that fewer spittlebugs means even fewer froghoppers – and the Meadow ‘Froghopper’ is a really interesting animal, if only because it looks like dozens of different species.

Bugguide Net has a great poster displaying some of the diversity of colour morphs found in this single species and this posting displays a few of the variants found in the HBG. It is a bit disappointing that we have so few froghopper species (only two, including the unidentified spittlebug on our birch), but the Meadow Spittlebug is a good reminder of the pitfalls of using skin colour as a guide in life. No matter what the colour on the surface, a miscreant may lie below.


  1. Great photos of the little guys. And thanks for the reminder to clean-up the perennial beds early in spring.

    Were the trapped parasitoid wasps intent on the spittlebugs? If so, there's a lot of natural selecting going on there!

  2. Hey Adrian,

    We've only rarely seen insects trapped in the Meadow Spittlebug spit (Heather rescued that particular shiny green pteromalid [?] - the free wasp is on her finger at the top of the post on Friendly Wasps). Of course, the MSB probably doesn't have a lot of specific parasitoids or there wouldn't be so many of them.

    The birch spittle was another matter - very copious, messy, and dozens, perhaps hundreds, of insects were trapped. For some it looked like bad luck - good luck for us when it was something like a tarnished plant bug - but a lot of the wasps appeared to be the same species and untrapped wasps were common around the froth. Something was going on, but what?

    I would expect a specific parasitoid of the birch spittlebug to avoid mass drowning in spit. So, my initial hypothesis would be that the wasps were intent on sugar or some other goody in the spit and that they stick their ovipositors elsewhere. Mother Nature is often portrayed as benign and in balance, but of course she is neither. I think this instance may be more of a La Brea Spitpit interaction, but can’t rule out a dynamic picture of selection between host and parasitoid. It is observations like these that make biology so fascinating.