Question - what stimulates larva to pupate?

[Mark Youles]

In article <20010701114443.3301.cpmta at c012.sfo.cp.net>,
speedshark2000 at altavista.com wrote:

>  Hi this is Heliconius and i'm a grade 8 student.
>  i would just like to know when does a caterpillar know it's time to make a 
>  chrysalis, or what stimulates it to do so. 
>  i would greatly appreciate it if you could email me your answers before July 
>  4

Without getting too compicated, the process is initiated in the insect
brain, where neurosecretory cells release Prothoracicotropic hormone
(PTTH) in responce to neural, hormonal or environmental stimuli.

It is interesting to note that the injection of this hormone into the
'mature' larval stages of some hawks moths (just prior larval 'shrinkage'
and pupation) have been shown to delay the pupation process and induce a
further 'giant' larval stage.

Hope this helps,


Mark

 
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