As most ELG silk moth enthusiasts know, the Robin Moth is a notoriously difficult species to raise through the larval stage & to successful pupation.

Many budding breeders have no problem getting past the first or second instar, but then a condition, which might be viral, seems to trigger an early death. Usually the larvae stop feeding, excrete liquids from mouth and anus then die.

This year I was determined to beat this problem. I obtained a supply of top quality ova from my friends Ian Mascall and John Kainec. The source was wild USA stock. I divided them into four batches.

• Batch number 1 was put onto cut lilac & cherry standing in water, in a ventilated cage kept between 20 & 25° C.

• Batch number 2 was put onto cut lilac & cherry in a ventilated plastic box & kept between 20 & 25° C.

• Batch number 3 was put onto potted wild cherry, which was kept in a cold house between 5 & 25° C.

• Batch number 4 was put onto a potted Liquidambar bush 2 metres high also kept in the cold house between 5 & 25° C.

Batches 1 & 2 followed the usual pattern & died in the second instar. Batch 3 simply refused to start feeding. Batch 4 however began to feed, albeit very slowly. The cold weather in June & July meant that for 18 hours a day the temperature fell below 15° C and was under 10° C for 12 hours. Days on end would pass without any discernable movement taking place. However, the larvae gradually increased their bulk and at each moult I observed them eating the cast skin before returning to the liquidambar. At the fourth instar the larvae were obviously very healthy and they started to wander around the bush. They would strip the end leaves off a branch and then cross to the other side of the bush before repeating the process.

August was very hot and the temperature often rose to 30° C or higher in the middle of the day. The larvae seemed no more or less inclined to feed in these conditions.

Eventually they spun up. I have checked the cocoons and they contain healthy wriggling pupae.

It is clear that cecropia is a species with particular needs. They cannot be crowded, but are not especially temperature sensitive. Foodplant is important, and particular strains may have preferences in this respect. It is wise to keep them dry. At no time did I permit rain to come into contact with my larvae, although I sprayed the liquidambar occasionally. The significance of the shed skin & the tendency of the larvae to eat it before returning to greenstuff cannot be underestimated. In the final instars, the larvae are great travellers (I found one cocoon in the leaves of the grapevine that grows along the roof of my cold house).

Next year I am going to use the same technique with columbia and euryalis, but I’ll need to buy a good supply of bushes as foodplants. The euryalis are supposed to do well on Ceanothus (Californian Lilac) so this is what I’ll offer.

Results published in autumn 2001!