Vapourer queries

[George Hogg]

Brought home a twig with several vapourer cocoons from a totally defoliated laburnum
All emerged as males and flew off
1 Are cocoons on twigs generally males
2 Are female cocoons generally on thicker branches
3 Is there any size difference between male and female caterpillars
4 Do female caterpillars stray as widely as males and take as long to enter pupal stage
5 Is Laburnum a common foodplant of Vapourer
6 Were the emerging males from this or last years caterpillars

Cant think of any more at present but no doubt I will !
George

[charlieb]

Originally Posted by George Hogg

1 Are cocoons on twigs generally males

Not that I'm aware.

Originally Posted by George Hogg

2 Are female cocoons generally on thicker branches

Originally Posted by George Hogg

3 Is there any size difference between male and female caterpillars

Not that I'm aware, although female caterpillars are twice, if not thrice the size of males so it would make sense, the larger caterpillars seeking out stronger twigs,

Originally Posted by George Hogg

4 Do female caterpillars stray as widely as males and take as long to enter pupal stage

That's a good question - I don't know! I would theorize that as the female caterpillars are bigger they would stray further (by virtue of being caterpillars longer) and would take longer to enter into pupal stage (again by virtue of being caterpillars longer).

Originally Posted by George Hogg

5 Is Laburnum a common foodplant of Vapourer

I've not witnessed them eating it, but they will eat a lot of things. See this list: BRC - Database of Insects and their Food Plants (as laburnum isn't native its probably not their "ideal" foodplant, nor will it be as commonly investigated for larva, which will also contribute to a lack of records)

Originally Posted by George Hogg

6 Were the emerging males from this or last years caterpillars

Vapourers can have two broods a year - so they could be this years or last years (it depends where you are - double broods are commoner in the south).

[George Hogg]

I am in Southeast Scotland.It is a fairly good butterfly year here so I assume a good moth year.If vapourers ever have 2nd generations here,I guess this would be a likely year for it.
Many thanks for answering my queries.I write the Country column in our local paper and so far have used pics of caterpillar and laying female from this tree.
About to continue the saga with pic of one of the males I hatched at home(collected Monday,emerged Friday)so your reply has filled a few gaps for me.
Thanks again...George

[charlieb]

Originally Posted by George Hogg

I am in Southeast Scotland.

I would have thought it highly unlikely that double broods would occur then, I think your a bit too far north!