Recognizing 5th instars

This topic contains 3 replies, has 3 voices, and was last updated by  BlueSkyBee 6 years, 6 months ago.

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  • #32952

    BlueSkyBee
    Participant

    I am  getting horribly short of food for my caterpillars now, so I’m taking the biggest fattest ones and putting them in ‘jail’ with slices of zucchini, which they do eat, luckily! The only thing is, I need to put more caterpillars away to try to save my plants which are looking pretty skeletonised about now, but I only want to grab 5th instar if possible. I’ve read that 5th instar will chew through the petiole of  the leaf so it hangs down, do 4th instar definitely NOT do this? Also apparently the spots on the prolegs are really quite pronounced on the 5th instar? I thought I’d read something about the markings on the head or ‘nosecone’ as I call it being unique, but I cannot find where I read it again…

    TIA 🙂

    Angie.

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  • #33073

    BlueSkyBee
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    Thanks for all that info Jacqui…

    Haha I’m not really game to put them in the fridge, I’m plying them with zucchini, and they are growing quite well, some had orangey/red frass, which freaked me out a bit, but when I looked it up, apparently the frass just before pupation can turn reddish, called ‘terminal frass’ so I’m seeing the light at the end of the tunnel! 🙂

    #33068

    Caryl
    Participant

    To my horror I found a caterpillar in salad greens which had been in the fridge for 4 days and half a day spent travelling from Wellington to Taupo. It was not at the stage you write about but I decided to put it outside on a bush (there were no swan plants at the resort) and the next day it was in a J form. Maybe sometime in the fridge would help the fat ones to the next stage???

    #32955

    Jacqui
    Moderator

    I’ve read that 5th instar will chew through the petiole of  the leaf so it hangs down, do 4th instar definitely NOT do this?

    Also apparently the spots on the prolegs are really quite pronounced on the 5th instar

    The black and yellow bands on the abdomen of a third instar larva are darker and more distinct than those of the second instar, but the bands on the thorax are still indistinct. The triangular patches behind the head are gone, and have become thin lines that extend below the spiracle. The yellow triangle on the head is larger, and the yellow stripes are more visable. The first set of thoracic legs are smaller than the other two, and is closer to the head.

    Third instar larvae usually feed using a distinct cutting motion on leaf edges. Unlike first and second instar larvae, third (and later) instars respond to disturbance by dropping off the leaf and curling into a tight ball. Monarch biologist Fred Urquhart called this behavior “playing possum.”

    Fourth instar larvae have a distinct banding pattern on the thorax which is not present in third instars. The first pair of legs is even closer to the head, and there are white spots on the prolegs that were less conspicuous in the third instar.

    The body pattern and colors of fifth instar larvae are even more vivid than they were in the fourth instar, and the black bands looks wider and almost velvety. The front legs look much smaller than the other two pairs, and are even closer to the head. There are distinct white dots on the prolegs, and the body looks quite plump, especially just prior to pupating.

    Fifth instar monarch larvae often chew a shallow notch in the petiole of the leaf they are eating, which causes the leaf to fall into a vertical position. They move much farther and faster than other instars, and are often found far from milkweed plants as they seek a site for pupating.

    (Thanks to the Monarch Larvae Monitoring Project)

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