Elephant Hawk Moth

[clicka15]

Originally Posted by rscott74

Actinic light? What's that exactly - drawbacks,cost,availablity,complexity etc. As I mentioned earlier I'm thinking of building a Skinner trap for next year - looking for easy/cheap first attempt.

Actinic is an alternative to mercury vapour (MV) that isn't so bright that your neighbours think dawn has arrived early! It's like the kitchen traps that electrocute flies, but without the zap. The advantage is less brightness in built up areas and being less conspicuous if you want to leave it overnight in the wilderness.

I opted for the twin 30W Actinic, so that I had 60W without the extra brightness. But this is one of the downsides: a 125W MV will attract more moths (and all the other seasonal beasties that go with them: Ophions, Crane Flies, Caddis Flies, etc) because it is brighter. Spare 30W actinic tubes are £15, which is fairly expensive, but because they don't heat up they tend to last longer (MV bulbs are literally white hot and will shatter in rain).

As you can see, there are advantages and disadvantages. I'm personally really glad that I went for the actinic set up. Even if I had no neighbours, my wife would moan if I used MV. And that would probably mean I was grounded on a regular basis.

Jon at Anglian Lepidopterist Supplies (ALS) is very helpful, but you said you wanted to make your own. May I suggest having a think about buying the electrics and making a DIY box? It could be safer (assuming you're not an electrician)!

Cheers,
Steven.

[johnny b]

Daft question time;;

Why such a big grub and only half the size moth.

[Harry Eales]

Originally Posted by johnny b

Daft question time;;

Why such a big grub and only half the size moth.

Helllo Johnny,

That's a difficult question to answer simply, but with moth larva for example, once the caterpiller is fully fed, it wanders off to find a place to pupate, this may involve travelling some distance before it (as with many moth species) starts to burrow into the soil, once it has burrowed down to the depth where conditions are suitable for pupation, it wriggles around to form a cell in which to make the change into a pupae. It may either exude an oily substance to bind the soil particles together, or, it may line the cell with a form of silk.

These acts will A. Burn up body fats and use up other chemicals within the body of the larva. Then there is B. The use of other chemical components to make up the pupal case. Both of which will reduce the larvae in size or volume.

Once the change into a pupa (which uses up additional cells from the larva) had been made the contents within the pupal case (for the want of a better word) dissolve into a fluid which, over the pupal period, reform into the cells which make up the adult insect. Some of these cells are waste products which are retained inside the developing moth and are later released after emergence in the form of a pink fluid called 'merconium'.

The adult moth has an exoskeleton made up of a substance called Chitin which is very dense and hard in which many millions of cells are compressed to form this hard outer skeleton. Such compression of cells are not present in the larva.

As far as I am aware, no one has ever experimented on the weight changes involved during the changed from larvae to adult insect. An interesting study perhaps for a students thesis.

The structure of the adult insect is much more dense than that of the larva, and when you compress any substance it will become smaller in volume, hence the obvious difference in size between the fully fed larva and the adult insect.

The adult insect emerging from the pupa is smaller than the fully fed larva, not perhaps half the size, but certainly smaller in size.

Harry

[goosey]

What a good question Johnny and a really informative and interesting answer Harry! WAB members are so great at getting people to think about something that may, or never have crossed their minds. I have learned something new today, again! Thanks .

[johnny b]

Wow,, Thanks Harry, one final question on the grub, what chemicals/substances makes up the large false eyes, ie colours and shape.

[Harry Eales]

Originally Posted by johnny b

Wow,, Thanks Harry, one final question on the grub, what chemicals/substances makes up the large false eyes, ie colours and shape.

Hello Johnny,

Skin colour and/or markings are made up of pigmentation cells. Larval colour and camouflage markings have evolved over millenia by natural selection to give the larva the best chance of survival from predators. In many species the larva can change colour during that stage of their life cycle.

The Elephant Hawkmoth larva for example, can be found in two colour forms, i.e. green and Brown. Usually the green form changes to brown during the moulting process often in the penultimate instar. In the Emperor Moth larva, these start of virtually black and as they grow they change to green and later they have purple wart like protruberances on each body segment making the large larva almost indistinguishable from the Heather on which it feeds.

One of the problems in identifying some larva is that some species have several colour forms and not all of these may be shown in textbooks on larval identification.

Harry

[rscott74]

Clicka15, thanks for info and advice. I'll make some enquiries - as Harry E also mentioned you need to get it right with outdoor electical equipment,