Alison brought some locusts, which she humanely killed by freezing them. After the session, the locusts were fed to Angie's chickens, so they were not wasted.
We heard a Bible story about plagues of locusts, and watched some film footage of locusts swarming.
Locusts are a type of grasshopper which has a swarming phase. They change from being solitary, relatively harmless grasshoppers to gregarious animals which band together in huge swarms. This change is triggered by overcrowding. It is an example of an epigenetic change. Epigenetic changes are those where there is a natural or regular change in phenotype (how something looks or behaves) without any change in the underlying genotype (its genetic inheritance)
(from What Is Epigenetics?)
"Epigenetic change is a regular and natural occurrence but can also be influenced by several factors including age, the environment/lifestyle, and disease state. "
Live Science on Locusts - nice article with some videos explaining the change from solitary grasshoppers to swarming locusts.
We incorporated the activities in the Nuffield Practical Science guide to investigating the ventilation system of a locust.
Everybody was given a petri dish containing paraffin wax, some pins, and a locust. First we pinned the locusts out, so that we could access the abdomen and thorax easily. Some chose to remove the wings and legs first, while others pinned them out of the way.
Next, we tried to locate the spiracles in our locusts, then we wanted to cut away a section of the top of the abdomen so we could look inside. We had to cut above the line of the spiracles.
We located the locust's heart, which was a red strand running down the back, and the alimentary canal (gut). Some locusts had faecal pellets in their guts.
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| The heart |
The structures we hoped to identify were the heart and the alimentary canal (digestive system).
Next, we poured some saline into the petri dish ('insect saline' , made up at the strength recommended for this activity, 0.9g salt in 100ml water). We looked for silvery threads floating upwards - these are part of the ventilation system, including tracheae and Malpighian tubes. You can see some good examples in the photos below.
I'll leave you with the clip that Alison found - why aren't insects really this big?
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| Ventilation system - the abdominal air sacs float upwards when immersed in saline. |
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