uneven sizes - Locusta

I always get very uneven sizes of locusta migratoria. Even if the pods are laid maximum a week apart, the resulting locusts seem to be much further apart, e.g. I get adults and moult 2-4 at the same time, same batch, same box.

Any ideas as to what might be causing this?

I've only been able to find that different temperature day/night can be causing this (http://birdcare.com.au/locusts.htm), however I've switched to constant temperature several generations ago.


  • edited May 21

    Hi slupik- I don’t rear locusts so am replying without personal experience with my idea.

    Normally Locusta migratoria have circulating (heamolymph) juvenile hormone during their 4th instar except on the last day of the 4th instar, when juvenile hormone is absent. Then in contrast normally L.migratoria in their 5th instar do not have circulating juvenile hormone except on the last day of their 5th instar, when juvenile hormone is present.

    Juvenile hormone is regulated by kinds of the neuro-peptide called allatotropin. If there are additional/extended moults this is due to the phasing of juvenile hormone creating a situation where there is more time to eat so it can go on to more likely to thrive as an adult.

    Farnesol in different forms experimentally causes a rise in juvenile hormone levels. In L.migratoria given a farnesol compound the impact on 5th instar was in it’s dynamic apparently time (day) sensitive.

    During the 5th instar L. migratoria were very impacted by farnesol application when they had just mounted. These 5th instar were affected by farnesol for up to 6 days & after that farnesol application had no significance.

    Frass has farnesol, but I lost the title of the old German report about this so can’t cite my source. My suggestion is to look at the amount of frass accumulated in your different batches & see if in any boxes some uneven accumulation of frass could be keying your variation.

    In other words consider the possibility excess local frass’ farnesol is causing some to still have circulating juvenile hormone on the last day of 4th instar. And then the continued over-exposure of frass farnesol still is instigating circulating juvenile hormone in the early days of the 5th instar.

    What can be done if this is actually the case? Maybe rig some design feature that lets you sift out some frass to a lower level after 4th instar moults. Out in the wild bugs aren’t living among accumulated frass & so outside of captivity it is insufficient food eliciting allatotropin that in turn would induce out of synchronization juvenile hormone.

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