The Small Hive Beetle, Aethina Tumida
Science Bulletin 220
UNION OF SOUTH AFRICA
DEPARTMENT OF AGRICULTURE AND FORESTRY
(Entomological Series 3)
A. E. LUNDIE, Ph.D.,
Research Apiculturist Division of Entomology, Pretoria
It is surprising that the insect to be described in this paper, although it is so common and can be so troublesome to the beekeeper, has not been mentioned previously in our apicultural literature. The absence of any mention of this trouble by beekeepers contributing to our journals is but another reminder that South African apiculture is still in its very infancy.
It is suggested that this insect, Aethina tumida, should be called “the small hive beetle” to distinguish it from another and much larger beetle, Hyplostoma fuligincus, which is also to be frequently found in bee hives in South Africa. Although the mature beetles are black, it may be well to avoid this adjective in any descriptive title to be given to the insect, because some beetles, on emerging from the ground, are a very light brown, and the period during which they turn from light brown to a dark brown and finally black is variable. However, the majority of these beetles after reaching maturity do not become active till a fairly high degree of pigmentation has set in.
The writer first became acquainted with this small beetle in 1924, shortly after hiving his first swarm of bees in Pretoria. A nucleus from this swarm was set aside for increase, but a later visit showed that the bees had absconded, and that the combs had become a seething mass of “worms”, which were easily recognized as beetle larvae.
Various facts about this insect and its habits were gleaned from time to time in practical work in the apiary, but it was not till 1931 that the writer, due to curtailment of his itinerant work, had the opportunity of commencing a detailed study of the insect. After further interruption the study was resumed in January 1938 and this paper gives the results of the investigations to date.
Our early entomologists received a few queries from beekeepers on an insect which was undoubtedly Aethina tumida, but in the absence of any detailed work on this insect it was suggested then that these beetles were probably not a pest, and that they were merely associated with the bees for the shelter and warmth which the hive and cluster afforded.
The first South African record of the insect is by Mr. R. H. T. P. Harris, who submitted specimens for identification from Durban in 1920.
Aethina tumida was first named and described by Andrew Murray in 1867 in the “Annals and Magazine of Natural History”, London, from two specimens which were sent to him by the Rev. W. C. Thomson from Old Calabar on the West Coast of Africa, but no mention is made of the insect being associated with honey bees in any way. This reference indicates that Aethina tumida must be widely distributed over the African continent. The writer has failed to find any other reference to the insect in the entomological literature available to him.
Aethina tumida belongs to the family Nitidulidae, about which W. S. Blatchley remarks that “The name Nitidula applied by Fabricius to the typical genus, is very inappropriate for the family, since it literally means shining or elegant, whereas the great majority of the species are clothed with a fine pubescence which does not permit of their to any great extent”. This fine pubescence is present in Aethina tumida.
The habits of this family were picturesquely described by Murray in the “Transactions of the Linnean Society”, London, in 1864, as follows:-
“The chief function of this family is that of scavengers. Their main business is to clear off decaying substances from the face of the earth, especially those minute and neglected portions which have escaped the attention of other scavengers whose operations are conducted on a larger scale. We may characterize them in one point of view as retail scavengers. They are, so to speak, users-up of waste materials. After the beast of prey has satisfied his hunger on the animal he has slain, after the hyena and the vulture have gorged themselves on its carrion, after the fly with its army of maggots has consumed the soft parts, after the burying beetles and the Silphidae have borne their part in the clearing away and when nought but the bones remain, then come the Nitidulariae to go over what they have left, to gnaw off every fragment of ligament or tendon and to leave the bones as nearly in the state of phosphate of lime as external treatment can. In another point of view, however, their employment is wholesale and wide enough. They conduct their operations all over the world, their branches extend into the most remote district; the materials with which they have to do, although mere waste, have no other limit to their variety or their number than the organized substances found on the surface of the globe. As in all great establishments, too, the principle of division of labour is carried to a great extent. Each different kind of substance has a different member of the firm told off to take charge of it. One species confines itself to rotten oranges, another to bones, a third to putrid fungi, a fourth to decaying figs. Decaying wood, decaying bark, decaying flowers, decaying leaves, all furnish distinct employment to different species. They are not all scavengers, however. Many pass their lives in flowers; others feed upon fresh victuals; and Mr. Frederick Smith, of the British Museum, has, while I write, brought to my notice a species of Brachypeplus (B. auritus) which he has received from Australia, in a wild bee’s nest, where it feeds, both in the larva and perfect state on the wax and honey.”
In discussing the Trigona or stingless bees of Australia in his book “A Cluster of Bees”, Tarlton Rayment mentions three beetles, Brachypeplus planus Er., Brachypeplus meyricki Blkb. and Tribolium myrmecophilum Lea and their association with these bees, but they are evidently not associated with honeybees in the same way as Aethina tumida, because he reports on the more abundant species B. planus, “Beetles placed on the combs of hive bees were immediately carried off by the workers”. Honeybees cannot eject A. tumida beetles so easily. These beetles can invade strong colonies of honeybees as well as weak ones with equal impunity.
These two references, both from Australia, are the only ones the writer has been able to find, which report an association of beetles and social bees which bears some similarity to the association of A. tumida with the honeybee in Africa.
Although A. tumida is not a major pest, there are localities where, and seasons when, it assumes such importance that it becomes almost as serious as the compolitan wax moth, and its control requires an equal vigilance from the beekeeper.
The absence of any reference to this beetle in our apicultural literature is probably due to the fact that most beekeepers who have been troubled by the larvae of this beetle have mistaken these larvae for wax moth larvae; and to add to their confusion combs are often infested simultaneously by the larvae of these two insects. The morphological differences between lepidopterons and coleopterous larvae are not generally known by laymen.
Although the beetles may be found anywhere in the hive, their favourite rendeavous seems to be the rear portion of the bottom board, where they probably escape to some degree the attention of both the bees and the beekeeper. Here not only are the beetles out of the maelstrom of traffic to and from the hive, but probably they can also secure their food, with a minimum of interferance from the bees, from the pellets of pollen that fall from the cluster of bees above them. The beetles, however, may be seen, immediately the inner cover is removed from the hive, lurking in the cavity behind the metal rabbets or in cavities in any burr-comb the bees may have built between the top bars of the frames and the cover of the hive.
When the frames of the hive are examined, these beetles may be seen running along the surface of the comb to disappear for a moment in a cell before emerging again to continue their scramble for a “safer” hiding place, perhaps in another cell nearby, where they may remain motionless and so escape the attention of the observer.One may also see a bee “close with” one of these beetles, curling its abdomen around the beetle in a vain endeavour to penetrate the hard chitinous armour of he intruding beetle, or the bee may be fortunate in getting a good hold of the beetle in this struggle and, taking flight, it “jettisons” the invading beetle at some distance from the hive. However, this does not appear to happen very frequently, for many beetles can live for long periods of time, even in strong colonies, with relative impunity.
THE NATURE OF THE PEST.
The small hive beetle is a scavenger, which may be likened to the cosmopolitan wax moth in many ways, but fortunately it is not nearly so destructive to the combs.
Just as the wax moths begin their ravages in combs in storage, or in weak colonies, so does the small hive beetle become a nuisance to the beekeeper. Any factor which so reduces the ratio of the population of a colony of bees to its comb surface that the bees are no longer able to protect this comb surface adequately is a precursor to the ravages of both the wax moths and Aethina tumida. Such factors as incorrect supering of the hive, excessive swarming, long standing European foulbrood, pilfering of some of the honey of the hive by thieves, who may pour water over the bees or use excessive smoke in obtaining their spoils, may result in a heavy infestation of Aethina tumida larvae, before the beekeeper is able to improve the condition of the colony.
The following are some of the principal occasions when a beekeeper may experience some trouble from this insect. Combs of honey that have to stand in the honey-house for a period before or after the extraction of the honey, are liable to become “wormy”, especially those combs that contain a certain amount of pollen. Cappings which are invariably set aside at extracting time by the beekeeper to be worked at a later date are liable to become “wormy” before they are melted down into cakes of wax. Honey left over Porter bee-escapes for several days before its removal may develop the larvae repidly as a result of the additional warmth which this honey gets from the colony of bees below it.
The larvae will pierce the cappings, side walls, and mid-rib of newly made or other relatively delicate comb, causing the honey to “weep” badly (Fig. 1 and Fig. 2), but old combs with several generations of cocoons can withstand heavy infestations well (Fig. 4) and can be used again in the hives after the gummy mixture of honey and larval excrement has been washed off with water under some pressure, such as that from a garden hose.
There are two characteristic conditions of the larval infestation which depend upon the relative abundance of honey and pollen in the infested area of the comb. When this area contains a small amount of honey and the larvae are feeding on the pollen mainly, their faeces have a dry “shredded” appearance, and the larvae themselves are a bright, dry, clean white; but when the honey being worked by the larvae is more abundant, this at first becomes discoloured, due to the faeces which the larvae void in the honey; then it becomes thin and ferments with a very characteristic odour, somewhat like that from decaying oranges. This odour in a honey room is usually the first warning to a beekeeper of the presence of active larvae in his supers. As the fermentation progresses, frothy bubbles ooze out of the cells of the comb (Fig. 1) and the “honey” falls to the bottom board where, in the case of an old infestation, it may accumulate sufficiently to run out of the entrance of the hive to the ground, or collect to form a layer an inch or more thick should the entrance become blocked or the hive bottom slope be to the rear of the hive. In this case the larvae become so thoroughly covered by the fermenting honey that they present an unpleasant slimy appearance, and when they begin to migrate away from this mixture, they leave trails of it behind them, discolouring everything over which they crawl.
With further fermentation and drying, the mixture of honey and larval excrement becomes sticky, and still later shrinks to a granular or somewhat spoungy mass, which can neither be scraped nor washed off easily from the bottom board. The full-grown larvae leaving the hive through any crevices large enough to give them egress on their way to the ground to pupate may carry a small proportion of this sticky mixture to the outside of the hive. Tracks of the mixture may be left in such quantities that in a heavy infestation even the outside of the hive may become quite badly discoloured [Fig. 5 and Fig. 6 (a)] by the hosts of migrating larvae on their exodus from the hive.
A perusal of Fig. 6 (b) will give some idea of the number of larvae which can develop in a few honey combs. This illustration represents a few of the dead larvae collected from the concrete floor of a honey room, where an infestation of some of the honey combs had occurred. These larvae died shortly after reaching maturity, having failed to find a suitable place on the hard concrete surface in which they could pupate.
Apiaries that have been established for a number of years are more likely to harbour a larger number of A. tumida beetles than recently established apiaries. Once a colony or a number of colonies in an apiary have retrogressed so far that these beetles have been able to breed in considerable numbers, other and normal colonies in the same apiary will harbour a greater number of these beetles, and there will be the danger that any supers from such an apiary will develop “wormy” combs rapidly, soon after they are left in storage in the honey-house.
One of the riddles of beekeeping is the total absence of American foulbrood in South Africa. This disease is prevalent in the Mediterranean countries and seems to be present in Northern Africa; but just why should Southern Africa be free of this disease, when conditions seem so ideal for relaying it down the length or “backbone” of the African continent? Perhaps in the warm tropics the rapid work of scavengers, of which the wax moths and Aethina tumida must play an important role, accounts for the absence of this foulbrood in Southern Africa.
DISTRIBUTION OF Aethina tumida.
In an attempt to get some information on the distribution of Aethina tumida in South Africa, a questionnaire on this insect, accompanied by specimens of the beetle, was sent to forty-four beekeepers of long standing. Only eleven beekeepers of the thirty-one that responded to this questionnaire showed that they were familiar with the beetle or its larvae. Ten of these beekeepers live in the low-veld or warmer areas of the Transvaal, and in the coastal areas of Natal and the Cape Province. One beekeeper on the Transvaal high-veld, who at first reported that he had never seen the beetle before, sent in specimens from his apiary at a later date. Beekeepers of very long experience in the Western Province and the Cape Midlands were not familiar with the beetle. Perhaps the climate and the nature of the soil militate against a rapid development of the beetle in these areas.
The presence of the beetle in Old Calabar, on the West Coast of Africa, suggests that A. tumida is widely distributed over the African continent, and in the absence of definite records it may be assumed that the beetle will be found in any of the tropical and subtropical regions of Africa.
CONDITIONS UNDER WHICH THE LIFE HISTORY OF Aethina tumida WAS STUDIED.
A knowledge of the inability of A. tumida to live long without regular supplies of fresh water and of the humidity requirements of the soil for the pupal period, gleaned from the 1931-32 study, enabled the writer to make more rapid progress in the 1938 study of this insect.
At first the full-grown larvae obtained from a heavily-infested hive were placed on damp soil in three types of containers:-
- Small tin boxes 1-3/4 inches in diameter and 1-1/2 inches high with transparent lids.
- Larger tin boxes, the diameter and height of which were about 3 inches to 3-1/4 inches, with loose-fitting metal lids.
- Glass battery jars about 4 inches in diameter and 6 inches high, covered with two sheets of transparent paper or muslin held in place by a strong elastic band.
There was a high mortality of the pupae in the small tins, due to the small volume of soil present and the free passage of air through the junction of the transparent material and the metal rims of the lids, which dried the soil rather rapidly. In spite of the larger volume of the glass jars and the use of paper covers to retard evaporation, the soil in these containers also dried out too rapidly.
The larger tin boxes proved to be the most satisfactory and were used throughout the greater period of this study. The soil was sifted through a piece of perforated metal with holes 1/16 inch in diameter and remained moist long enough for several generations, without any addition of water. The degree of moisture which was maintained in these tins may be judged by the ease with which several specimens of the common earthworm (Lumbricus sp.) grew to a length of about three inches in the soil in some of these tins and were kept in this way with no further addition of moisture for several months.
All the tins were kept on a table in an unheated room some 12x12x12 feet in extent and having a window (3×6 feet) on the north side of the building. The room was used as the writer’s office. Its temperature would approximate that of any medium-sized honey-room used by beekeepers in extracting and storing their honey.
The adult beetles were kept in the larger tins. They were removed daily to a clean tin containing fresh food and a clean piece of cotton wool soaked in water, except at the week-ends, when the beetles would be two days with one lot of food and water. The food supplied was a mixture of honey and pollen, thoroughly worked together to form a thick paste. The larvae were also fed on this mixture, but no water was supplied to them. The ease with which A. tumida can be bred in tins or petri dishes and the longevity of the insect, would make it a very suitable one to breed for general laboratory purposes or for museums exhibiting live insects.
THE LIFE HISTORY OF A. tumida.
The Egg. – The eggs of A. tumida are arcuate pearly-white objects [Fig. 7(b)], 1.4 m.m. long by .26 m.m. wide, similar in appearance to the eggs of the honeybee but smaller, being approximately two-thirds the length of the latter.
The eggs are deposited in irregular masses by the female (Fig. 7a) which seems to prefer some crevice or cavity for oviposition. In ascertaining the period of incubation of the eggs, bits of comb containing honey and pollen were at first supplied to the beetles to oviposit in, but it was found that eggs could easily be overlooked in these bits of comb, so later pieces of comb foundation, on each of which a drop of the honey and pollen mixture was placed, were supplied to the beetles. Eggs were laid on the bottom of the tin, on the strips of foundation, and in some tins many eggs were deposited in the clearance space between the flange of the lid and the metal rim of the lid, as well as between the fibres of the cotton wool holding the water. Eggs were found in the crevices between the successive layers of silk woven by the honeybee larvae in the bits of comb at first supplied to the beetles.
The appearances of masses of small larvae in cells containing pollen would suggest that in nature the beetles probably deposit their eggs in or on the pollen masses in the comb or in cells adjacent to them. Over thirty small larvae have been counted from a single cell containing pollen. Data on the incubation period of the eggs were obtained throughout the whole of February, March and the first week of April. Out of 1,299 eggs, 72 hatched in 1 to 2 days, 1,010 in 2 to 3 days, 204 in 3 to 4 days, 11 in 4 to 5 days and 2 in 5 to 6 days.
The number of eggs which a single female can lay in her lifetime was not ascertained, but practical experience has taught that two or three beetles in a pile of supers can cause a heavy infestation of “worms” due not only to the reproductive capacity of the females, but also to their great longevity. (See “Longevity”, page 15.)
The Larva. – The larva emerges from the egg shell through a longitudinal slit at the anterior end. The small newly emerged larvae have a peculiar appearance on account of their relatively large heads and numerous protruberances all over their bodies (Fig. 8a), which appear to protect the insects from being smothered by the honey when they feed.
There is a great variation in the rate of growth in a number of larvae of the same age; the majority will mature in ten to fourteen days, but a fair number will feed at least a week longer (Table 2). These slow maturing larvae are usually smaller in size, and they give rise to smaller beetles. A relatively large number of these late maturing larvae also die soon after they have gone into the ground before reaching the pupal stage. On the other hand pre-adult mortality is very low in the quicker maturing larvae.
The majority of the larvae grow to a length of 3/16 to 1/4 inch when four days old, and when full-grown (Fig. 3 and Fig. 8b), they attain a length of 7/16 of an inch and a diameter of slightly more than 1/16 of an inch.
At the commencement of this study the larvae were supplied with small bits of comb containing some cells filled with pollen and other cells filled with honey, but as the study progressed it was found to be more convenient to prepare a stock mixture of approximately equal quantities of honey and pollen and to provide the larvae with a small portion of this mixture at regular intervals. Most of the larvae were reared in the small tins described above. During their development they would remain on the bottom of these tins feeding on the mixture provided, but as soon as they reached maturity they would crawl over the whole surface of the tin, including the lid, in their endeavour to find a place to pupate.
When most of the larvae in a small tin had reached this stage, they were placed in the lid of the tin, set on the surface of some damp soil in one of the larger tins so that those larvae that were ready to pupate could enter the soil, and those that had to continue to feed could do so from the honey and pollen mixture placed in the smaller lid. After all the larvae had entered the soil, the lid containing the food was removed to avoid an excessive development of mould, which grew in the mixture when the latter was kept in such a damp state. The larvae are very sensitive to light. In the tins receiving some illumination they would always retreat to the darker portions, or get under any opaque objects that could shelter them from the stronger light. On a warm sunny day larvae kept in direct sunlight are soon killed.
On two occasions the larvae carried so much of the honey and pollen mixture with them in their migrations around the tin that the air space between the lid and the tin itself became closed by the mixture and all the larvae in the tin were suffocated.
On entering the soil the larvae makes a smooth-walled earthen cell (Fig. 8c) in which it pupates. In very damp soil these cells are sometimes connected by a tunnel to the surface of the soil and the larvae may return to the surface before pupating. It is during this transition from the larval to the pupal stage that the insect is very vulnerable, and in nature there must be a very high rate of mortality during this period. The nature of the soil on which an apiary stands must play a very important role in determining the relative abundance of Aethina tumida in the hives. Further investigation will probably show that the absence of A. tumida in certain areas is due to the physical or chemical nature of the soil, which would cause a high mortality of the larvae at this critical stage of their development.
The Pupa. – The pupa (Fig. 8c and Fig. 9c and 9d) is pearly white with a series of very characteristic projections on the thorax and abdomen. As the pupa changes to the adult stage, pigmentation sets in, at first in the eyes and then in the under wings, which lie ventrally and shine through the more transparent elytra partly covering them. In the last period of development a frequent twitching of the tarsal joints of the limbs of the maturing beetle can be seen within the pupal skin.
The period spent in the soil varies a great deal, as may be seen from the chart (Fig. 10) or Table 3, which shows that this period may vary from 15 to 60 days. The majority of the larvae emerge as beetles after a period of three to four weeks in the ground.
By sifting the soil before the larvae went into it to pupate, and again after most of the beetles had emerged from it, the mortality in the pupal stage could easily be determined. A very small proportion of the larvae which entered the soil failed to reach the adult stage and these seem to have been killed by a fungus.
The Adult. – The newly-matured adult (Fig. 9a and 9b) is a light yellowish brown, becoming successively brown, dark brown and finally black as it ages. These changes in color usually take place in the pupal cell before the beetle emerges from the ground, so that most beetles are quite black when they emerge; but a fairly large proportion of the beetles emerge from the soil when still a light brown, and they do not become a distinct black till some three or four days later. During the first day or two after their emergence from the soil, the young beetles are very active, take flight readily, and make for the light; but later they become less active, rarely use their wings, and keep to the less illuminated portions of any receptacle they are placed in.
The females begin to oviposit about a week after they have emerged from the soil. The beetles show a great variation in size, but most of them are approximately 3/16 of an inch long, being about 1/2 as broad as they are long. The larvae that mature first become the larger beetles and the slow-maturing ones the smaller. The smallest beetle reared in the course of this study was approximately half the length of a normal-sized beetle.
The longevity of fifteen Aethina tumida beetles were studied during the period December 1931 – March 1932, and that of fifty-three beetles in the period January-August, 1936. At first a large number of beetles were placed in a bell jar covered with muslin. They were given a piece of comb containing cells of honey and pollen, and water was supplied on a piece of cotton wool at regular intervals, but with so many insects in such a large receptacle it was difficult to keep accurate records, so the method was abandoned in favor of the small tins, not more than five beetles being kept in a single tin; fresh supplies of food and water were given regularly as previously described.
The data obtained have been summarized in Table 4.
Although the longevity of only sixty-eight beetles was determined, the data show a fairly even distribution at all ages from a few days to a longevity of over six months. Forty of the sixty-eight beetles lived fro over two months.
In the hive where presumably the beetles can get within the more congenial temperature of the cluster of bees it is possible that the beetles can live even longer than these figures would lead us to believe. It is this great longevity, and its consequent overlapping of generations, which makes the presence of this insect in the apiary or the honey-house a constant source of annoyance to the beekeeper.
THE DIET OF Aethina tumida.
In an attempt to ascertain whether the larvae of Aethina tumida could mature on a diet of honey alone, a number of larvae were placed in a petri dish and fed with honey. The first experiment was undertaken in 1932, when one larva lived for seven weeks in the honey; this larva, however, was of unknown age at the beginning of the experiment, being about 3/8 inch in length, which suggests that it must have been about seven days old before its diet was confined to honey. Further, the honey used in this first experiment was not strained to eliminate all pollen grains.
In the 1938 study, however, the experiment was repeated with larvae that had just hatched, and the honey was strained through a thick piece of cotton wool. Of this sixty-one larvae supplied with this honey, two died on the first day, fifty-one died in two to four days, six in five to eight days and two died after fifteen and nineteen days respectively. Here again even in the oldest larvae there was a decided lack of growth.
Although no larva was ever actually seen to eat other larvae, the disappearance of considerable numbers of newly hatched larvae from some of the tins in this experiment might have been due either to cannibalism or to a consumption of the bodies of the early deceased larvae, which might account for the survival of the few that lived so much longer than the others on the honey diet.
The pollen, as packed into the cells of the combs by the bees, was fed alone to Aethina larva; these larvae matured at the same rate as other larvae fed on the honey and pollen mixture.
The writer has not been able to discover just why certain apiaries always harbour a relatively large number of Aethina beetles in the hives, whereas other apiaries a few miles distant are relatively free from the beetles.
The presence of some abundant food source outside the hive may be the correct explanation of this difference in the beetle population of the two localities, and pollen is more likely to be that source.
Beetles confined in test tubes will readily eat eggs and larvae of the honeybee supplied to them, but it is questionable whether much damage is done in this way in the hive. A colony in which some four hundred beetles were liberated showed no abnormality in the development of its brood. Beetles in confinement will feed readily from a drop of honey or pollen supplied to them.
NUMBER OF GENERATIONS.
Five complete generations of A. tumida were obtained in the calendar year 1938. No eggs were obtained from the beetles after 15th April, and the first spring larvae were observed on 24th August. In other words, no oviposition was observed during the four cool months extending from the middle of April to the middle of August.
Since the eggs can be overlooked so easily, the tins in which the beetles had been kept were examined daily for the presence of larvae, which, on account of their movements, can be discerned easily.
Due to the great longevity of A. tumida and the relatively long period required to complete a generation, there must be a very considerable overlapping of generations, which would continue until a particular food source became exhausted; thus in any hive in an apiary that has become heavily infested with A. tumida will breed many beetles to infest other and healthy stocks in that apiary, and this explains why an old-established apiary is more likely to harbour more beetles than a recently established one which has not yet had any of its colonies heavily infested.
PARASITISM OF Aethina tumida.
Neither in the course of his general apiary experience nor in this study has the writer observed any signs of insect parasitism in A. tumida. A large number of larvae (Fig. 6b) swept up from the concrete floor of a honey-house were kept under observation for the emergence of parasites but without result; further, no parasites emerged from any of the three thousand odd larvae brought in from the apiary and kept in damp soil to complete their development to the adult stage.
On several occasions Microbracon brevicornis Wesm. has been reared from the larvae of the common wax moth, Galleria mellonella, taken in the environs of Pretoria. Since the small hive beetle and the wax moth larvae are often found infesting one and the same comb, it was thought that M. brevicornis might breed in the beetle larvae as well as in the wax moth larvae, so some fifty A. tumida larvae were at different times exposed to those parasites, not more than five larvae being present with one group of the parasites. The female parasites stung the Aethina larvae readily and fed from the puncture holes they made in the larvae, in spite of the presence of honey and water in the cage, but no parasites were reared from these larvae, all of which died on the second or third day after being stung.
Combs in storage that have become heavily infected by the larvae of Aethina tumida may be fumigated with carbon bisulphide at a minimum dose of one ounce of the liquid to three deep Langstroth hive bodies. Combs with minor infestations can be returned to the bees to be cleaned, but those with heavier infestations should be washed in water prior to their return to the hive. A hose pipe with a fair amount of pressure is to be preferred for this purpose. Strong colonies should be selected for the cleaning work and only a few of the infested frames should be inserted in the hive at a time. The bees, although they rarely succeed in ejecting the adult beetles from the hive, have no great difficulty in removing the beetle larvae from the combs.
The writer, when using a carbolic cloth to remove honey from a hive, has observed that the Aethina beetles seemed to respond more rapidly to the fumes than the bees do, because they came out of the supers through all the openings available to them, somewhat before the bees in the same supers had moved down in large numbers to the lower parts of the hive. This fact might be useful to a small beekeeper, who can take the time to kill the beetles as they emerge from the hive under these conditions. Some beetles can also be trapped under small boards placed over the holes of the inner cover so as to provide a small space between the board and the inner cover in which the beetles can hide. This method can also be used to reduce the number of chelifers in a swarm that may be harbouring a large number of these peculiar little creatures.
For the commercial honey producer there seems to be no thorough practical measure that he can take against the adult beetles in his hives, but ordinary good sanitation and the use of standard equipment make the control of the larvae a relatively simple matter. In the apiary house all bits of comb and cappings should be rendered down into cakes of wax as soon as possible, and not be left about long enough to afford a breeding place for the beetles. Combs in storage should be examined at least once every three weeks for the presence of larvae. In the apiary itself, weak colonies should be united with other colonies, re-queened, or strengthened in some other way, or the comb surface reduced so that the bees present in the hive can protect adequately all the comb surface available to them.
- Aethina tumida was first described by Andrew Murray in 1867 from two specimens sent to him from Old Calabar on the West Coast of Africa. It is believed that the present paper is the first report on the insect as an apicultural pest.
- The larvae of the beetle are particularly troublesome in weak colonies and in combs in storage. They feed on honey and pollen and do damage to the comb, but they are not as destructive as the cosmopolitan wax moth larvae, G. mellonella.
- A. tumida is probably widely distributed in all the tropical and sub-tropical regions of Africa. In South Africa it seems to be more prevalent in the warmer areas.
- The insects were reared in small tin boxes, which were found very suitable for the purpose.
- The eggs hatch in two to three days. The larvae mature in ten to sixteen days and pupate in earthen cells in the soil. Three to four weeks later the adult beetles emerge.
- Under laboratory conditions the beetles lived for over six months. They probably live longer in the more congenial conditions of the hive.
- The larvae must have a diet of honey and pollen to reach maturity. Larvae fed on honey alone do not grow.
- Five generations were reared in the calendar year 1938.
- No insect parasites were reared from A. tumida.
- Combs infested with the larvae of A. tumida can be fumigated with carbon bisulphide at the usual dosage for wax moth larvae, namely, one ounce of the liquid to three Langstroth hive bodies. Combs in storage should be examined every three weeks. Moderately infested combs can be washed with water and returned to the bees to be cleaned. The bees, although they rarely succeed in ejecting the adult beetles from the hive, have no great difficulty in removing the beetle larvae from the combs.