BARBERRY CARPET MOTH Third Report C. W .
PIERCE
IN the last report it was stated that twenty-seven pupae remained from the second brood of 1971, and from knowledge of what happened in the spring of that year, it was not unreasonable to suppose that emergences in 1972 would occur at about the same date. Thus when I went to Gibraltar for a month from the beginning of April, I expected that none of the moths would have emerged during my absence. Unfortunately, when I returned on 4th May, I found that all of the twenty-seven had emerged, most of which had died. However, some had mated and I was able to find sufficient ova to keep the colony in being and to produce twenty-five pupae for the second 1972 brood. The larvae fed on both Berberis thunbergii and B. vulgaris var. atropurpurea and seemed to thrive on these cultivated forms as well as on their natural wild common barberry. The moths started to emerge early in July, 1972, at least four weeks earlier than in the wild, as was the case in the previous year. There was a greater number of males than females, and for this reason the number of pairings was smaller than the eighteen successful emergences would leave one to expect. It is possible that this preponderance of one sex may have been due to the moths having come from eggs deposited at the end of the laying. Finally, forty-seven pupae were raised ready for 1973, when it was hoped that the resulting imagines, after mating, would be released at a new habitat in which the planting of 100 bushes of the common barberry had been planned. However, it was not possible to get the planting carried out before April, 1973, and because it would have been unwise to have released the moths until the plants had become established, it was necessary to continue breeding the captive colony for a fourth season. By 9th May, 1973, sixteen imagines had emerged and mating started. My diary records that sixty larvae were feeding on 26th May, when, for family reasons, I had to leave at short notice for Gibraltar. Fortunately, I was able to hand over the whole colony to Mr. Richard Luff, of Needham Market, who kindly agreed to care for it during my absence. At this time the moths were in various stages of their life cycle. There were laying moths, small larvae, larvae at the last instar as well as some pupae from 1972. When I returned to this country and relieved Mr. Luff of his bĂźrden on 18th June, about 150 larvae and pupae had been
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produced. By Ist July about forty had pupated, and, after the usual mortalities, some fifty larvae remained at differing stages of growth. I had for some time been very concerned about the State of the colony, and there were now signs that seemed to confirm my fears. It must be remembered that the colony had been started with far too small numbers and it had not been possible, because of the destruction of the original habitat, to acquire fresh stock. Firstly, five moths appeared on 2nd July while there were still twelve larvae not yet ready to pupate. Secondly, about one third of the pupae (in the end round about seventy) produced moths early in July, whilst the remainder did not appear until mid-August. T h e r e was a period of nearly five weeks between these dates when no emergences occurred. Thirdly, in contrast to last year's second brood when males predominated, this time there were far more females. Fourthly, although most of the females laid, the majority of the ova proved to be infertile. These facts suggested that the colony should be transferred to a natural environment as soon as possible. After discussion with Mr. Edgar Milne-Redhead, it was decided to put roughly half the larvae and ova on a large common barberry bush at Nayland, not far from his home, where he could make some observations next year. T h e other half would go to the new site which was planted in the spring. In spite of all the troubles experienced, over 600 larvae and many fertile ova were obtained and on 16th August half of these were placed at Nayland. On the next day, most of the remainder were taken to the new site on Major Agnew's estate, not far from the moth's original home in Shakers Lane, Bury St. E d m u n d s . It would have been preferable to have released all the brood in one place, but it was feit that the newly planted barberry was not yet large enough to have supported the whole colony. As an insurance, ten pupae from the last brood are being retained for release in 1974. T h e r e are also some larvae, at the time of writing (22nd September) "sleeved" on two small barberry bushes in my garden. If these complete their life cycle successfully, they, too, will be placed at the new site in 1974. As this is likely to be the final report, it would perhaps be instructive to mention some of the difficulties encountered and mistakes made since this project was started, if only to avoid them if i t i s found necessary to carry out s a l v a t i o n O p e r a t i o n s on other species. 1. It is essential to get a new habitat prepared as soon as possible. T h e food plant should be given the opportunity of reaching a reasonable size before the insects are released. Valuable
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time has been wasted by purists arguing about the desirability of introducing a moth in a new site. T h e original site should be studied and species associated with the foodplant should be established at the same time. If this project fails, and its success is by no means assured, this failure is most likely to be due to the enforced Inbreeding, through eight generations, of a captive colony started from a dangerously small number. 2. It is unwise to leave the care of a colony to one person only, especially if the breeding has to be extended for more than a year. That person may not be able to look after the feeding of the larvae over long periods, as he may, as I was, be called away on occasion. Also, if the numbers of larvae become large due to successful breeding, the task can be too great for one person to manage. Preferably, the project should be controlled by a small dedicated committee. 3. Great care must be taken to ensure that no predators are on collected food. I lost some larvae by not noticing some diptera in their early stages. 4. Although I was not guilty of ignoring the hygienic aspects, it is essential to keep all Containers clean and to replace food frequently. T o prevent an epidemic spreading through the colony only small numbers of larvae should be in each Container. For the same reason, it is desirable that more than one person should share in building up the numbers. In conclusion, I should like to thank those who have given help in various ways. Messrs. John Trist, Peter Wright, and Edgar Milne-Redhead are to be thanked for their part in getting permission to plant the new site at Rougham and for getting the planting carried out. Messrs. David Chipperfield and Peter Wright helped with the experiments on alternative foodplants. Mr. Richard Luff took care of the colony at a critical time this year. Lastly, special thanks are due to Major Agnew for agreeing to the setting up of a new colony on his estate, and to the Suffolk Trust for Nature Conservation for purchasing 100 young plants of the common barberry.
Reference Pierce, C. W . (1970). Barberry Carpet Moth. Suffolk Natural 15, 273. Pierce, C. W. (1971). Barberry Carpet M o t h . Second Report. Natural History 15, 511.
C. W. Pierce, 14 Clialkeith Road, Needham Market,
History Suffolk
Suffolk.