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Overwintering the Tigers

Reg Fry

The Tiger moths (subfamily Arctiinae) are some of the most enjoyable species to breed (if at times frustrating) and many lepidopterists cannot resist breeding them again and again when they come across ova or larvae on field trips. Those species which overwinter as pupae are easy to rear in their hundreds or even thousands but the most variable in both markings and colour hibernate as larvae and are often extremely difficult to overwinter without very high losses. The purpose of this article is to record my own experience with a few species and to encourage other lepidopterists to let us know of methods which they have found to be successful - or otherwise!

The Garden Tiger, Arctia caja Linn., must be the most frequently bred in captivity and in the largest numbers because of the extreme variation in both markings and colour of the adult moths. However, all the lepidopterists I have spoken to find it difficult to hibernate the larvae in captivity without very high losses and many resort to breeding the species continuously. Most larvae which die appear to have been attacked by a type of mould or fungus which is presumably due to damp perhaps coupled with a lack of ventilation. If this is the case one wonders how high the larval losses are in the wild - perhaps its survival is due to the fact that the female is quite a prolific layer and hence the species can tolerate high losses.

Over the years I have tried overwintering on different species of plant both in wood and netting cages in a cool spot in an open stable and on sleeved plants with a cover over the top to prevent direct rainfall. None of these have been very successful with at best perhaps 10% surviving. It is possible that part of the problem is that because the females lay so many eggs there is a temptation to group too many larvae on one plant which gets contaminated with frass which tends to hold moisture. In fact on reflection the conditions which produced the lowest losses were when I left some fifty or so larvae in a small cardboard and netting cage with a few crumpled sheets of kitchen roll in a cool dry shed with no foodplant - practically all the larvae survived!

For those that have not tried continuous breeding in captivity I have found the following method produces the most successful results. I usually start by rearing the larvae (Fig 2) in small plastic boxes lined with kitchen roll to keep the foodplant dry and fresh (I always start with dock as they seem to thrive on this) moving them to progressively larger boxes with fewer larvae in each as they grow. Naturally the boxes need to be kept scrupulously clean and dry. They are kept indoors in a temperature around 18°C. When they reach a size of about one and a half centimetres long they would normally go into hibernation but if you keep them indoors you will find that around 30% will continue feeding. At this stage I usually move them into a wooden and netting cage (still indoors) and it soon becomes obvious which larvae will continue feeding and which will not. This is the time to put those that stop feeding in cool dry conditions outdoors to hibernate or you can simple release them into the wild.

Fig 2 - Larva of the Garden Tiger

You may find you are able to feed this first generation on dock up to pupation. If not (and for feeding over the winter), I always use so-called spring greens, which are usually available from supermarkets. I have generally found Tesco's spring greens to be the best, other sources have not proved to be as reliable. For example, I once tried greens from a supposed organic shop but they gave the larvae a dose of diarrhoea - from which they recovered when I reverted to the usual source! The major problem of course is that you (and the family) have to put up with the smell of cabbage throughout most of the winter although this is not too bad if they are cleaned out every day! For pupation I have found the best method is to suspend the large papier mache egg trays from the roof of the cage.

When the adult moths emerge you will obviously have to decide which males and females you want to pair - depending on whether you are trying to breed a particular variation or colour form. I bred the pure yellow form for many generations from a male which I was delighted to find in my MV trap in July 1987. Sometimes one wants to pair up brother and sister to experiment with a particular variation but I have found that they are usually reluctant to do so for at least a couple of days, whilst unrelated couples will often pair up on the first night after emergence.

Curiously I have found that in the second and subsequent generations a higher proportion of larvae will feed up to pupation without hibernation. In fact after four or five generations virtually all would do so. Some reports in old journals suggest that it is necessary to keep the larvae in the dark to breed them continuously but I have not found this to be necessary. The previous Bulletin editor, Brian Gardiner, warns against keeping the larvae in temperatures over 20°C as he has found that this can produce infertile females (pers. comm.).

Another moth of this subfamily which I have bred on many occasions is the Scarlet Tiger, Callimorpha dominula Linn. Personally I have had very little success in overwintering these larvae in captivity although a friend who had several clumps of comfrey, Symphytum officinale, growing in his garden had some success by putting them out on the plants unsleeved when they were ready to hibernate. When I lived within a reasonable distance of a strong colony I used to return the young larvae to the wild when about to hibernate, collecting up a few again the following spring.

I have only bred the Wood Tiger, Parasemia plantaginis, on one occasion. My wife found a nearly dead female when we were out for a walk near Cheddar in Somerset. The moth was in very poor condition and clearly on its last legs. However it managed to lay five eggs before it expired. These all hatched and again by keeping them in the warm they fed up and pupated with the adults emerging in the autumn. The larvae were initially fed on plantain but in their final stage had a strong preference for brussel sprouts cut in half. The adults paired easily and I bred a second generation that winter but unfortunately the third generation died in the pupal stage.

I used to breed the Cream-spot Tiger, Arctia villica Linn., (Fig 3) regularly as a lad when I lived in Bournemouth but this was easy as there were a couple of superb localities (now both horrible housing estates) where the larvae were common in the spring and very easy to find. I have only bred it once in recent years when I found a female, which unusually was attracted to an MV light. The larvae were kept on a potted foodplant in a cool shed and as I recall the losses during the winter were not that high and I bred a reasonable number through to adulthood. I would be very interested to hear of the experiences of other lepidopterists with this species. In his book Moths and Memories by P.B.M. Allen (1948) he states that he had no difficulty in overwintering the larvae on groundsel or dock but could never persuade them to continue feeding after mid-March, and suggests that those living in the south of England did not experience the same difficulties.

Fig 3 - The Cream-spot Tiger

I have never had the opportunity to breed the Jersey Tiger, Euplagia quadripunctaria Poda, but the few people I know who have tried to, have all lost their larvae during hibernation.

The Ruby Tiger, Phragmatobia fuliginosa Linn., is often double-brooded in the south of England and the few times I have bred it have resulted in adults the same year without any difficulties.

Finally the Clouded Buff, Diacrisia sannio Linn., This was a common moth on several of the Surrey heaths where I used to live. The larvae were relatively easy to find after hibernation and so I never tried to hibernate them myself.

I hope this article will result in other lepidopterists recording their methods for successfully overwintering these species, particularly the Cream-spot, Jersey and Scarlet Tigers.

If you have time to write for The Bulletin yourself we would be pleased to receive notes from anyone who has had success with these species.

Originally published in the Volume 57 of the Bulletin of the Amateur Entomologists' Society.

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