Silkworm Reproduction

I lift the lid. I know the sound by now; a desperate throbbing of wings. Two silk moths huddles together - the tip of his abdomen inserted into the tip of another. I feel like I shouldn't be watching, but I do. In fact, I am mesmerised.



Clearly it requires effort. Slowly, it seems, this male moth is pumping all that remains of his life into hers. All those days of eating, eating, eating - all for this. It goes on and on, day after night after day. A short rest and then he starts again: a fast beating of the wings, the tiniest shove. And she just sits there. Fatly immobile. Docilely smug. As soon as she emerges they are after her. A little eau de Bombxyol behind a middle segment and she could be anyone's.

Then, a day or so later, they will mysteriously detach. He might busy himself with a search for another, but shortly thereafter he will die. She, meanwhile, will excrete one glistening yellow drop of liquid - the remains of whatever toxins remain inside her - and then will start to lay her eggs. She places them delicately, her abdomen tip describing circles and lines, one egg and then another, beads the size of pin heads, a production line of seeds to harden, darken and eventually become another - just like her.

A Menage a Trois

Well there are only five occupied cocoons now - and so far my cocoons have yielded five females and twelve males; five of these males are of course very happy... and the rest very frustrated. So frustrated, in fact, that this morning I discovered that one newly-emerged female was somehow mating with two males at the same time (I did not take photos). I prized off the more disreputable-looking one and put the remaining pair in the 'ovarium'.

Here is a short clip I took a couple of days ago of a recently-emerged female attempting to dry off, and the males just starting to pay her some attention.




I wonder if it is usual to have such an imbalance of males and females. I know in other insect colonies this is the case, and I can see why - but I don't really see why there should be in a population of silk moths.

An Unhealthy Obsession.

Great excitement among my male silk moths this morning; each one was wildly flapping his wings. The reason was that another female moth had emerged. Already one male had mated with her, and another was trying to attach himself to her too. Now that I know about the pheromone, it all makes sense.

I removed the extra male as gently as possible, and then put the mating pair (stripy male and female) in another box to give them a little peace. At once the rest calmed down. That pheromone is a powerful molecule, but it seems that once the source is removed the effect soon fades away.

I then managed, at last, to separate yesterday's happily mating couple (stripy female-unstripy male), removed the male, and after waiting a few seconds replaced the paper under the female - which was now dirty. She then promptly started to lay her eggs. It were as if I had given her permission.

I am trying to leave the silk moths alone now, and divert my mind back to the Patagonia novel. I want to try and finish the Tehuelche edits this week because I have to give in the revised manuscript to my editor at Seren in March.

The Clinch.

In fact there was no need to do my light experiment, because when I woke this morning I discovered that two more moths had emerged overnight and one of them - which was huge with eggs - was in the process of being fertilised by one of waiting males....So maybe they were all males after all.

I have tried to separate them just now because I thought they had been mating long enough (they are only 'supposed' to mate for three hours) but I was unable to break their clinch. I have transferred them to my 'ovarium' (a box with a wet flannel over the top inside another box with a lid in an attempt to keep them humid enough).


I have also put them on some glossy paper in case this proves to be a better medium for eggs than newspaper.

Egg Laying.

I took another photo of the mating moths this afternoon,



then, when I checked on them again this evening found them detached, but still close together on the same cocoon. Unable to decide which was male and which was female, I pulled them gently away from the cocoon and placed them on some newspaper in their own private place.

Now the female moth is supposed to be larger than the male, but the smaller one seeemed to have the fatter more feminine body.
'I think the big one is the female,' I said to Hodmandod Senior, 'but it's difficult to tell, isn't it?'
'Well I think it's the other one,' he said, 'because she's the one laying the eggs.'


And so she was, one after the next, tiny pale yellow thing the size of pin heads, conveniently on the black print of the newspaper.



I have left her in peace to finish her work - by the time she finishes there may be close to 400 of them. Getting them to hatch sounds like it might be the most difficult task of all.

Emergence Day!

I just looked under the flannel this morning, not expecting to see much, but instead I saw this!


Three moths have emerged, and two of them (at the top) are mating already. They seem to exude a sticky substance when they come out which stick the cocoons together so I am going to space the rest out, and also try and check them in the early hours which is when they tend to emerge. I wonder if it was the damp flannel that did the trick. No doubt I shall write more on this later, but in the meantime here is a little film...