Speaker: Chris Hassall
Sunday 8 September 2013
This month’s talk, by Chris Hassall, was on camouflage and mimicry. (It also involved chocolate AND a quiz, for which the speaker gets a gold star.) Animals and plants can benefit either by not being seen (camouflage) or by being mistaken for something that they are not (mimicry). Our speaker began by telling us about Abbott Thayer, an artist and naturalist who came up with ideas on defensive colouration, identifying three types: disruptive, as with zebras en masse being indistinct one from another; masquerade, mimicking something in which the predator is uninterested, like an insect looking like a leaf; and counter-shading, involving varied shading and use of light. US President Teddy Roosevelt, an avid game hunter, criticised the assumption that all camouflage was defensive, and Chris explained this with examples demonstrating competing interactions for advantage by animals, insects and plants.
Then came the chocolate bit. Revels, to be specific. For those not aware of this Russian roulette of confectionery, each bag contains six different types of sweet, of varying shapes: Maltesers, sort-of-Minstrels, toffees, orange and coffee creams, and raisins. As many people don’t like one or more of these, strategies abound to distinguish between the shapes, but these can fail: for example, fully confident in my Malteser choice, I was disappointed to find I had accidentally picked an oversize orange cream.
Anyway… while we all rootled for toffees, Chris told us about Henry Walter Bates, another naturalist, who looked at the patterns on butterflies. Some butterflies that were poisonous were wisely given a wide berth by potential predators, but it turned out that other, non-poisonous butterflies got wise to this advantage and evolved to look like the poisonous ones. Clever, huh? This evolution stuff never ceases to amaze me.
There was a lot more to the talk, including varying forms of males and females to avoid harassment, aka ‘sneakomorphs’, the hawk-tailed drongo bird who imitates warning signals in order to steal food, and finally some big questions: why aren’t all mimics perfect, and why aren’t all animals/etc. mimics? Disclaimer: apologies if I’ve got anything wrong, but I was somewhat distracted by an unfortunate selection of a coffee-flavoured Revel and rather lost my flow of note-taking while spluttering.
Then it was quiz time, which the speaker has kindly allowed me to reproduce here. See how you do. Below are twelve pictures. Which five of these insects could sting you? (Answers below.)
Answers, left to right: top row: ouch, ouch, safe, safe; middle row: ouch, ouch, safe, safe; bottom row: safe, safe, safe, ouch.