caterpillars development

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    Jean Stanley

    Having given 153 caterpillars away this week my plants are still loaded with caterpillars but there is little feed left, and I have run out of friends.

    Is it known if once a caterpillar reaches a stage (age) and runs out of feed that it will move on to the next stage of development where it doesn’t need feed or is it doomed?


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    I got given a pumpkin ages ago by a neighbour that was going soft. I quickly cut it into chunks and stored them in the deep freeze. I put chunks in the castle to defrost and be eaten. The caterpillars didn’t seem to have any problem eating big grooves into it, but previously I’ve used strips of fresh pumpkin from a potato peeler so I wondered if that was part of the problem



    Sounds like an excellent idea, Darren.

    When you say “frozen” pumpking… what do you mean exactly? I’ve only ever used strips of fresh pumpkin.



    Our FAQ says when they are ten days old or more than 2cm in length they can finish off with cucumber, pumpkin, or courgette.

    I tested this for myself recently using frozen chunks of pumpkin and 10 caterpillars 3cm or more. I used the main batch of caterpillars I took those 10 from as a control and kept feeding them swan plant. The control group did well, with only a handful of deaths in well over a hundred, say >95% survival which I was pleased with considering how crowded they were. To be a proper control group I should have taken 10 and moved them to another castle so they were in the same conditions as the test group, but I had been given roughly 200 caterpillars and my resources were stretched.

    The test group of 10 had a 60% survival rate. 2 died as caterpillars, and two failed to completely form a chrysalis.

    So either I was very unlucky and 10 wasn’t enough for a statistically accurate sub-sample, the caterpillars didn’t like the chunks or the fact the pumpkin had been frozen, or it really is a last-ditch backup when you know the caterpillars are going to die anyway if you do nothing.

    Also I unfortunately moved all the chrysalises to my hatching container so I cannot say if there were further difficulties once they had successfully formed chrysalises. That could have lowered the 60% figure even further.

    In hindsight if I were going to repeat this experiment I would take 20 small caterpillars and rear them together. Then I’d put 10 in one castle and 10 in another. I’d feed the control group swan plant and the test group thin slices of fresh pumpkin. I would allow them to form their chrysalises in their castle and leave them there until they emerged, noting any abnormalities. That would give a better control group and a more relevant result over all their life-cycle.

    The study could be further enhanced by having multiple test groups, e.g. 1 for pumpkin, 1 for courgette, 1 for cucumber to compare each individual feed. I would also like to see what happens to a test group fed on pumpkin AND cucumber AND courgette simultaneously. Is it possible that each substitute feed is missing some vital ingredient, but it is a different ingredient in each case? That way a combination might be more successful than any of the individual substitutes.

    If a number of us did this then it would also be independently verified. Now that’s getting into some serious citizen science!

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