BUTTERFLIES IN SUFFOLK S . BEAUFOY

THIS article is not a comprehensive survey of all the butterflies of Suffolk; but it is a review of the present-day status of some of the county's species, both common and rare, with special reference to the scarcity, or even possible disappearance, of some of the rarer species. An attempt is made, as well, to find a plausible explanation for this reduction in numbers. Conditions in the countryside have changed considerably since the days before the last war — much of the heath and rough meadow land has been ploughed and cultivated, hedges have been uprooted and many of the deciduous woods have been felled or replanted with conifers. As a result it is inevitable that the total number of butterflies has decreased. Recent observations, however, indicate that the commoner species are still very common indeed, at least in suitable localities near Ipswich. T h e r e is no dearth of many species of the Browns: the Ringlet (Aphantopus hyperanthus), the Hedge Brown (Maniola tithonus), the Meadow Brown (M. jurtina), the Small Heath (Coenonympha pamphilus) are always abundant in and around Belstead Woods and elsewhere, as are the two Skippers, the Small Skipper (Thymelicus sylvestris) and the Large Skipper (Ochlodes venata). T h e Whites are also plentiful in Suffolk; the Large White (Pieris brassicae), the Small White (P. rapae), the Green-veined White (P. napi), the Orangetip (Anthocharis cardamines) are common and widespread. T h e r e is also a fair sprinkling of the Common Blue (Polyommatus icarus) and the Small Copper (Lycaena phlaeas). A butterfly, which in some years is scarce, the Holly Blue (Celastrina argiolus), was in 1968 exceedingly numerous in both the spring and autumn generations in the Ipswich area. T h e Small Tortoiseshell (Aglais urticae), the Peacock (Nymphalis io) and the Comma (Polygonia c-album) have remained fairly common over the last few years. T h e presence of the Red Admiral (Vanessa atalanta), the Painted Lady ( V . cardui), and the Clouded Yellow (Colias croceus), of course, depends upon immigration to this country from abroad in the early summer. So m u c h for the commoner species. T h e same happy State of affairs does not hold for some of the scarcer species. T h e following species have been absent from the Suffolk countryside since about 1960, or have been recorded in only a few isolated instances — White Admiral (Limenitis Camilla), Purple Emperor (Apatura iris), High Brown Fritillary (Argynnis cydippe), Silver-washed Fritillary (A. paphia), Pearl-bordered Fritillary (A. euphrosyne), Large Tortoiseshell ( N y m p h a l i s polychloros), and Silver-studded Blue (Plebejus argus). It has often been suggested that the increased use of chemical sprays has been the cause of the reduction in the n u m b e r of

BUTTERFLIES IN SUFFOLK

43

butterflies to be seen. T h i s Statement is generally m a d e without the slightest justification or evidence to s u p p o r t the claim. I t may be true to say that the n u m b e r of wayside flowers has been reduced by the use of sprays on roadside verges, but this reduction is relatively small and there are plenty of flowers left for the b u t t e r flies to feed on. A study of the larval foodplants of different species will show that sprays will have only the very slightest effect u p o n the abundance of these plants. It has, for example, been suggested that the killing of stinging nettles by sprays has accounted for the alleged absence of Small Tortoiseshells, Peacocks, Red Admirals, and Commas, whose larvae feed u p o n this plant. I n the first place, it should be pointed out that these species are not at all u n c o m m o n ; and secondly, that stinging nettles are a b u n d a n t everywhere, only an extremely small proportion being destroyed by sprays, so that the destruction of larvae in this way m u s t be negligible. It should be pointed out that the seven scarce species mentioned above are, with the exception of the Silver-studded Blue, mainly woodland species and, even at the best of times were not very common, s o m e being confined to particular woods and not to be found in others — the P u r p l e E m p e r o r , for example, has been recorded f r o m only one wood in Suffolk in recent years. In this locality also were to be f o u n d the other woodland species; b u t this wood has in the last few years been drastically cut, which probably has accounted for their disappearance f r o m it. T h e r e are, however, m a n y other woods in Suffolk which in the past harboured some of these species, b u t where today few, if any, are t o be f o u n d . It is illogical to suggest that these disappearances are d u e to chemical sprays, which are not used in such areas. T h e same may be said of the Silver-studded Blue, which used to be f o u n d commonly on some of the ling-covered heaths in Suffolk. T h e s e areas, although not so extensive, are still in the same State as they were previously, when t h e butterflies were plentiful on t h e m . T h e L a r g e Tortoiseshell is not essentially a butterfly of the woods, but inhabits also lanes and thickets where elms grow. In years gone by this butterfly was widespread t h r o u g h o u t the county; b u t its apparent disappearance is most unlikely to be caused by the use of chemical sprays. Some other reason, then, than the use of sprays, the felling of trees and t h e cutting of hedgerows, must account for the disappearance of these butterflies. It is p e r h a p s significant that many of t h e species are, in Suffolk, at the edge of their ränge in this country (for distribution maps, see F o r d , 1967), or have never been widely distributed t h r o u g h o u t the county, although in the past they have been fairly c o m m o n within isolated localities. A possible reason for the reduced n u m b e r s may be f o u n d f r o m a study of the climatic conditions in Suffolk d u r i n g the last few years. I am very grateful to M r . F. J. Bingley, of Fiatford Mill Field Centre, for allowing m e to consult t e m p e r a t u r e records taken at

44

Suffolk Natural History, Vol. 15, Part 1

East Bergholt from 1954 onwards. been plotted from these records:

T h e following graphs have

(1)

mean annual temperatures,

(2)

mean temperatures for the five summer months, May to September, during which the insects are active, either as butterflies or as feeding larvae,

(3)

mean temperatures for the seven remaining months, October to April, during which the insects are in the dormant, hibernating stage.

F r o m (1) it will be seen that the annual mean from 1957 to 1961 was above the average for the years 1954 to 1967. T h i s was followed by a sharp fall in 1962 and 1963 (in 1964 it rose slightly above the average, but feil again in 1965). A study of (2), the temperatures for the summer months, shows that there was a sharp fall in 1962, with a rise in 1963 and 1964, and another sharp fall in 1965. T h i s general lowering of the temperature after 1961 in the summer months, when the insects are active, may have been suffkient to reduce the numbers of the scarcer species during these years to very low figures, even to extinction point; but the lowering of the temperature is unlikely to have permanently affected the numbers of the commoner species, which were more widely spread, and which had greater reserves from which to build up their populations again. An examination of (3), the temperatures for the winter months, also shows a general decrease in temperature from 1960-61 to 1962-63. This fall, however, is unlikely to have caused the decrease in the n u m b e r s of the butterflies, as it is generally accepted that cold winters favour the insects in the dormant stage, as they are then less likely to awake prematurely from hibernation. T h e r e are always considerable fluctuations in the numbers of a particular species from year to year and from decade to decade, and also in the distribution of a species throughout the country over a period of years; it is well to remember that there are notable increases as well as decreases, as shown, for example, by the spread during recent years of the White Admiral throughout southern England to as far west as Devon, and the spread of the Comma from a small area around Hereford right across the East Coast, and northwards to Yorkshire. There is always the hope, therefore, that some of the species which have not been seen in Suffolk in recent years may spread back again, or that a 'missing' species may still exist in the county, although in such very small numbers as to escape Observation. It is possible that these butterflies may suddenly increase in numbers and so give pleasure to those of us who visit the countryside during the summer.

45

BUTTERFLIES I N SUFFOLK

MEAN TEMPERATURES, EAST BERGHOLT (1) Mean annual temperatures

tost

S

Z

7

fl

3

i960 /

2

3

5"

6

/St7

(2) Mean temperatures, May to September

65 °F

60

.—"" 55 135-1- 5

&

T

8

3

s

i960

\/ I

2.

Aver i g e

3

4-

5

6

/967

(3) Mean temperatures, October to April

fQSi/s sj(, 6/7 7/a

ifa. 2/3

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References Ford, E. B. (1967). London; Collins.

Butterflies

(New Naturalist Series), 3rd edition,

Symes, H . (1967). £W. / k W 79, 12. de Worms, C. G . M . (1968). Ent. 101, 1261.

S. Beaufoy, M.B.E.,

B.Sc.(Eng.), F.R.E.S., Ipszvich, Suffolk.

98 Tuddenham Road,