This month, Deputy Keeper of Natural History, Emma-Louise Nicholls, tells us all about noisy grasshoppers.
'A plague upon both your houses'
Grasshoppers are those cute, colourful, hoppy insects you may have run around in circles trying to catch as a kid. Grasshoppers are also the thing of nightmares, capable of gathering in their billions and swarming across the land, much to the chagrin of Ancient Egyptians and modern farmers alike. It is only a small number of grasshopper species that form these gargantuan, crop-decimating swarms, causing mayhem and bringing dishonour to the good name of grasshoppers worldwide, earning them the alternative name of locust.
A locust is just as much a grasshopper as any other species of grasshopper, but their gregarious phase sees them swarming in groups of up to 50 billion individuals. A swarm of this magnitude can weigh up to 79 tonnes. To give you some context, that’s more than 13 adult male African elephants, or if you’d prefer the equivalent of 10 Tyrannosaurus rexes. I’d say everything is better if the unit of measurement is dinosaurs. Locust swarms of this size will decimate the land by consuming around 192,000 tonnes every day until it dissipates. That’s 32,000 African elephants worth of crops being eaten. Or 24,000 T. rexes…either way, the take home message is it’s a good job they’re vegetarians.
A Rhythmic Symphony
There are lots of insects that look like grasshoppers but only those within the suborder Caelifera are ‘true grasshoppers’. They’re also known as the short-horned grasshoppers which refers to their antennae length, they don’t have actual horns.
Grasshoppers make their chirping sound by rubbing a series of small pegs located on the inside of their hind legs across their forewing. In general, male grasshoppers have evolved to deploy this to greater effect than females as grasshoppers primarily use the sound to attract a mate or repel a rival. Both of which seem to be a ‘boy job’. Grasshoppers have a number of different ‘songs’ depending on what they are doing, their favourite of which, I am sure, is the ‘Copulation Song’.
The act of rubbing two body parts together is called stridulation. Whilst this fancy term is primarily used in relation to insects, some spiders and snakes also use stridulation. A few species of grasshopper take a slightly different tack and produce sound by snapping their wings together in flight, akin to the sound my knees make when I stand up after a three-hour board game. The snapping noise made by grasshoppers (and my joints) is referred to as 'crepitation'. Two great words for your next pub quiz.
If true grasshoppers decided to join forces and work out how to alter pitch and coordinate a harmony, they would have the means to rival the best orchestra in the land. It’s not particularly likely to happen anytime this side of a lot of evolution as at present, the 21st Century grasshopper can hear intensity and rhythm, but really struggles to differentiate between pitches. So they’d be pretty rubbish in the performance of all scores bar the most basic of percussion segments.
The metal parts in our giant Grasshopper means it does a lot of crepitating. The Robot Zoo exhibition is open until 29th October 2017.