Bishybarnabees Col., (Coccinellidae)

TRANSACTIONS BISHYBARNABEES COL.,

(COCCINELLIDAE)

G . D . HEATHCOTE

THE local name for coccinellid beetles in Suffolk is 'bishybarnabees' (Bishop Barnabys), but more generally in England and in many parts of the World they are called 'ladybirds', 'ladybugs' (i.e. 'Our Lady' beetles) or the equivalent in the local language.

They are some of the few insects generally 'populär' with the public, and have their own nursery rhyme—'Ladybird, ladybird, fly away h o m e . . . w h i c h probably arose from the custom of burning hops after harvest. Around Long Melford they were called 'rainy bugs', and it was thought that it would rain if one was killed (Ambrose, 1972), but I have not heard of that superstition applied elsewhere. Dr. E. A. Ellis (personal communication) suggested that the name bishybarnabee derives from the fact that they are active about St. Barnabas day, l l t h June, and that is certainly a time at which many 2-spot ladybirds (Adalia 2-punctata) are caught on traps at Broom's Barn Experimental Station, near Barrow.

There was widespread interest in ladybirds in 1976, with BBC 2 television producing a programme called 'The year of the ladybird'. Many people claimed to have been bitten by them—a bite causing a painful swelling. In fact, the jaws of a ladybird are not particularly large or strong and, although Dr. P. F. L. Boreham of Imperial College, London, is reported in The Times as finding human blood in their gut (by the use of a technique involving an antiserum), what probably occurred more often was that in the hot, dry weather the beetles were only trying to obtain moisture by drinking sweat. When disturbed, they exude a pale yellow liquid from their leg joints ('reflex bleeding') and as this is caustic it can cause distress if it penetrates the skin.

Unusually large numbers of the large, red, 7-spot ladybird (iCoccinella 7-punctata) flew in the summer of 1976 in Suffolk and in many parts of England. T h e Eastern Daily Press on 13th July reported that 'Hunstanton was under siege' and that 'holiday makers fled the beaches'. Reports of 'plagues' tend to be from north Norfolk rather than from further south in East Anglia, e.g. Heathcote (1972) reported one at Snettisham in 1971, but Baron de Worms (1962) described another at Walberswick.

Incidentally, although both these swarms were primarily of the 7-spot, they also contained the 4-spot (Harmonia 4-punctata) which is not one of the more common species in Suffolk.

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Large numbers of ladybirds were commonly found well into the winter of 1976-77, the adults hibernating under dead leaves, in rabbit burrows and in houses, but they could also be found stationary, scattered on bushes in sheltered woodland, giving the appearance of hawthorn berries. Many died in the cold, wet months that followed.

T h e general name 'ladybird' Covers a widely-distributed group of beetles of which more than 3,000 species are known, and there are forty-two species found in Britain. Most are named according to the number of spots on the commonest form of the species.

Of course adult beetles cannot grow, nor does the number of spots increase with age as is popularly supposed but, as the number of spots on individuals of a single species can vary considerably, other features have to be used to identify them with certainty. Young adults of the species which are red with black spots may be pale yellow and lack spots when they emerge from their pupal case, but they develop the adult colours within a few hours. T h e 2-spot ladybird is particularly variable in colour pattern. It is usually red with black spots, but it may be black with red spots and the proportion of the population that are predominantly black ('melanics') varies with the region. In Manchester and in Glasgow, where there is considerable industrial pollution, up to 95% of the population are black, but the proportion of melanics has decreased with the pollution in recent years (Creed, 1975). T h e red forms predominate in Suffolk.

At Broom's Barn, ladybirds regularly hibernate between doors and door frames of two little-used entrances to the buildings, and almost exclusively 2-spots, e.g. in 1976 there was only one 7-spot and three 11-spot ladybirds (Coccinella 11-punctata) and none of them was close to 2-spot individuals. Each species gives off a characteristic odour (a 'pheromone') which encourages them to 'aggregate' at suitable sites. T h e melanics formed less than one per cent of the population in recent years, e.g. in 1971, 180 beetles were examined and 175 were typical red ones with a single black spot on each wing case, one was black with red spots (var.

6-pustulata), one had one small extra black spot on each wing case (var. stephensi) and three had the black spot extended sideways (var. rubiginosa).

In 1976, 659 were examined; 656 were typical, one was black with four red spots (var. 4-maculata), there was one var. rubiginosa and one had irregulär black spots similar to var. annulata.

As all colour forms are distasteful to birds there should be no selective loss from predation, although the 'warning colour' is more obvious in the beetles which are predominantly red. A possible reason for the melanics being at an advantage in certain regions is that they will absorb heat more readily than the red form and therefore can be more active in cool weather (Muggleton, Lonsdale & Benham, 1975).

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The life history of ladybirds varies from species to species, e.g. the 2-spot generally has two generations each year ('multivoltine') in England whereas the 7-spot has only one ('univoltine'), and so conditions which favour one species will not necessarily favour another. Their relative abundance may differ from year to year, but both 7-spots and 2-spots were common in Suffolk in 1971, 1975 and in 1976.

The fluctuations in the numbers of 2-spots hibernating at Broom's Barn are interesting in relation to the number of aphids found in the following season, even if they do not reflect the numbers of all ladybird species. Aphids are the normal prey of most ladybirds, although there is one plant-feeding species (Subcoccinella 24-punctata) in Britain which occasionally becomes a pest to gardeners, and another (Thea 22-punctata) which is quite common in Suffolk, which feeds upon mildew and therefore aids the gardener.

The 2-spot tends to feed on aphids infesting low bushes (Ipertini, 1966) and is therefore the ladybird most likely to control the black bean aphid (Aphis fabae group) which overwinters as eggs on spindle bushes, hatches in spring and multiplies there before moving to attack our beans or sugar-beet crops.

A. 2-punctata overwintering and numbers of s o m e winged aphids caught on a sticky trap at Broom's Barn in the following season A.

1972 1973 1974 1975 1976 1977

2-punctata

180 13 3 65 119 659

A.

fabae

36 494 1,693 53 4 —

M.

persicae

13 65 142 104 98

830 1,423 1,830 3,867 3,645

—

There is an obvious trend for the relative numbers of 'blackfly' in spring to decrease as the numbers of 2-spots overwintering increases, but this does not necessarily apply to all species of aphids, e.g. the peach-potato aphid ( M y z u s persicae), which is the 'greenfly' most likely to spread virus diseases in crops.

Unfortunately 2-spots do not thrive when feeding on 'blackfly', laying only half as many eggs as when reared on 'greenfly' (Blackman, 1967). Some black aphids, e.g. Aphis sambuci which feeds upon eider, are actually poisonous to ladybirds.

If ladybirds are active when aphids colonize crops they may have an appreciable effect on the development of the pest population. For example this is true of the 7-spot and sugar-beet crops (Heathcote, 1963), but control of an aphid population by a predator—one of its natural enemies—depends not only on its abundance, but also on its appetite, its activity and the relative

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LADYBIRDS—(clockwise) eggs, larva attacking an a p h i d a n d p u p a of Coccinella 1 -punctata, a n d a d u l t of Adalia 2-punctata, var. typica. ( b o t t o m row, left to right) A. 2-punctata var. stephensi, var. rubiginosa, var. quadrimaculata a n d var. sexpustulata f r o m B a r r o w , Suffolk.

E g g s and adult 2 spot X 10. Larva and p u p a x 5.

BISHYBARNABEES

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reproductive rates and synchronising of their life cycles. Ladybirds do not feed during winter, relying on stored fat, and if they become active in spring before aphids are abundant they may starve. Ladybirds will either fly away or starve if food is scarce and only lay eggs (yellow, barrel-like, usually in groups of five to eight on leaves) where they find food. Any aphids that survive the initial attack will reproduce rapidly once the ladybirds have dispersed, and there is therefore little point in rearing ladybirds and releasing them as adults to act as 'bio-control' agents.

Ladybird larvae are predominantly black with yellow or white spots and resemble miniature crocodiles. They are voracious feeders, and are not able to fly away when food becomes scarce.

They are therefore more likely to have an effect on the aphid population than the adult beetles. Dixon (1970) found that newly-hatched 2-spot larvae require at least two small aphids per 100 sq. cm. of leaf if they are to survive, but their chance of survival is increased by the brutal fact that they are cannibals and on hatching immediately eat their unhatched brothers and sisters (Dimetry, 1974). Under warm conditions it requires a beetle-aphid ratio of perhaps only 1 :200 to suppress the pests on sugar-beet crops, but in cooler conditions it may require one of 1 : 30-60 (Hodek et al. 1966). T h e whole story is a complex one and the sudden decline in the aphid population that so often happens in late summer is partly due to the aphid's reproductive rate declining because of crowding, less suitable food, high temperatures, etc., as well as to the activity of ladybirds and other natural enemies, but even if we cannot use 'bishybarnabees' as natural insecticides, they are attractive creatures and help us to control pests and we should encourage them.

References A m b r o s e , E. (1972). Melford Memories. L o n g M e l f o r d Historical a n d Archaelogical Society.

B l a c k m a n , R. L . (1967). Ann. appl. Biol., 59, 207-19.

C r e e d , E. R. (1975). Proc. R. Soc. Lond. B., 190, 135-48.

D i m e t r y , N . Z . (1974). Entomophaga, 19, 445-51.

Dixon, A. F . G . (1970). J. Anim. Ecol., 39, 739-51.

H e a t h c o t e , G . D . (1963). PI. Path., 12, 80-3.

H e a t h c o t e , G . D . (1972). Suffolk Natural History, 15, 515.

H o d e k , I. et. al (1966). Proc. Symposium Ecology of Aphidophagous Insects, Prague.

Ipertini, G . (1966). Entomophaga, 11, 203-10.

M u g g l e t o n , J., L o n s d a l e , D . & B e n h a m , B. R. (1975). J. appl.

Ecol., 12,451-64.

W o r m s , Baron de (1962). Suffolk Natural History, 12, 55.

Dr. G. D. Heathcote, 2 St. Mary's Square, Bury St. Suffolk.

Edmunds,