Sunbathing caterpillars (1 Viewer)

[Saerwen]

While out walking on heathland today, we came across several large, very hairy caterpillars sat on the paths, not moving. I found the caterpillar in a reference book which confirmed they were Fox Moths which apparently overwinter as larvae then emerge "briefly, without feeding again, to bask in spring sunshine".

Can anyone tell me why these larvae bask in the sun, surely it makes them vulnerable, although most birds probably wouldn't like their hairs. Do they have the same problem as reptiles and snakes, needing to raise their body temperature? I hope this unseasonally warm weather hasn't convinced them it's spring, or they're in for a shock.

 

[harry eales]

While out walking on heathland today, we came across several large, very hairy caterpillars sat on the paths, not moving. I found the caterpillar in a reference book which confirmed they were Fox Moths which apparently overwinter as larvae then emerge "briefly, without feeding again, to bask in spring sunshine".

Can anyone tell me why these larvae bask in the sun, surely it makes them vulnerable, although most birds probably wouldn't like their hairs. Do they have the same problem as reptiles and snakes, needing to raise their body temperature? I hope this unseasonally warm weather hasn't convinced them it's spring, or they're in for a shock.

Hello Saerwen,

The larvae you saw on the heathland were probably moving from one plant to another. They are far more visible on a footpath, even if grass covered, than they are when on their foodplant. The reason that they were stationary is most likely a protective measure. Something moving is easier seen than something that it not. It would have picked up the vibrations of your feet hitting the ground as you walk. Even we humans say 'freeze' or 'don't move' if we don't want to be noticed.

Hairy larvae, especially those of moorland moths have uricating hairs which gives them good protection from many predators, it works with many humans as well who are sensetive to these hairs.

Fox Moth larvae are unusual in that they 'sunbathe' after coming out of hibernation. They certainly don't feed in spring when fully grown. Perhaps the sunlight triggers something (perhaps the silk producing cells for spinning their cocoons) or it may have some other purpose. I don't think anyone knows for certain.

Harry

 

[Saerwen]

Thanks for that explanation, my first instinct was to pick them off the path to prevent them being squished, but maybe that's not a good idea if their hairs cause rashes, and they might not thank me for moving them further away from their food!