The fascinating secrets of waste analysis

Too often, the drawer is used solely to detect the presence, more or less abundant, of natural debris from dead varroa mites. Yet the drawer is a mirror of the life of the colony just above it… If the beekeeper takes the time to examine it regularly, the observed elements, waste, fragments, and other residues provide valuable information about colony dynamics and health. Examination of the drawer must always be correlated with the beekeeping calendar: the interpretation of a drawer inspected in summer will be very different from that of the same drawer opened at Christmas.

Inspecting hives during overwintering is inadvisable, even on a fine sunny day. The colony, which forms a winter cluster to minimise heat loss and optimise its food consumption, must not be disturbed.

When disturbed, the winter cluster tends to break up. The increase in volume of this cluster is associated with an increase in its surface area, hence greater heat loss and increased oxygen exchange with the cluster core, which in turn leads to increased heat production and higher fuel consumption. Opening the hive would needlessly chill the colony and destroy the propolis bridges that provide a good seal against draughts.

Entrance observation provides little information, as bees fly little below 8–10°C. The alighting board sometimes shows a little condensation water, which reassures the beekeeper: this physical phenomenon confirms that warm, humid air (produced by the colony) is coming into contact with cold air (present inside the hive or near the entrance grid) or a cold solid, such as the hive wall or crown board.

Estimating the weight of stores by lifting the back of the hive is at best subjective and often does not allow one to confirm that all is well inside the hive…

We are therefore left with examination of the varroa monitoring board. This removable device, located beneath the open mesh floor of the hive body, collects the debris produced by the colony. This debris falls through the floor grid with the comings and goings of workers and settles on an oiled or unoiled insert in strips parallel to the frames, sometimes interrupted by cross-members of the hive floor.

The varroa monitoring board is examined after having been placed under the colony for 48–72 hours. Too often, the board serves only to detect the more or less abundant presence of naturally fallen dead varroa mites. Yet the board is a mirror of the life of the colony directly above it… If the beekeeper takes the trouble to examine it regularly, the elements, debris, and other residues observed yield valuable information about what is happening between the frames of the hive body, where the colony resides. Examination of the varroa monitoring board must always be correlated with the beekeeping calendar: a board examined in summer will look very different from the same board opened at Christmas.

1. Colony Strength and Position

Visible debris rows correspond to debris falling from the bee spaces between the frames. These rows make it possible to locate the colony's position and assess its strength. In winter, the winter cluster tends to position itself near the hive wall that is warmed by sunlight, often the south-facing side. Counting the debris rows makes it possible to determine the number of frames between which the colony clusters, and therefore the approximate size of the cluster.

The debris strips indicate the volume and position of the winter cluster. The brood nest expands as spring approaches. If colony development stagnates or even regresses, the beekeeper will carefully examine the brood to find a clear cause. Inspecting the queen is also essential to verify her age (declining egg laying) or any possible requeening followed by incomplete or absent mating (virgin queen).

• No action required.
• If the colony remains roughly the same size or decreases in size, this may indicate a brood or queen problem.
   

2. Worker Activity

More careful observation of the debris present in the rows gives us valuable information about worker activity. Dark brown debris corresponds to uncapping of honey stores: the colony is consuming fuel so that the cluster core can heat the queen, any very slightly developed brood, and the peripheral layers of the cluster mantle, whose temperature must not fall below 6°C. It should be recalled that below 6°C, bees become torpid and eventually die of cold.

3. Difficult-to-Interpret Insert

This insert is difficult to interpret, as it was in place for several days or even weeks. The debris deposits are too thick to yield reliable indicators about the health of the colony. The dark brown rows in the centre correspond to uncapping of old sealed stores. The lighter-coloured rows correspond to uncapping of more recent stores. It can be assumed that the colony has changed position according to the location of its stores, as it is improbable that it occupies 10 complete frames (11 rows)… A little mould at the bottom of the photo evidences condensation above the entrance grid.

4. Type of Food

Small translucent crystals resembling crystallised sugar with a sweet taste when placed on the tongue come from the consumption of syrup/fondant.

White micro-crystals (image below) resembling flour, without a sweet taste, correspond to the consumption of melezitose or possibly another highly crystallised sugar requiring a great deal of energy to dissolve (set honey, e.g. ivy honey).

(Photo: S. Imboden, 30 December) Photos 7, 8, 8b (S. Imboden, 22 December): It is possible to determine the type of sugar: above: crystallised sugar (syrup/fondant) below: melezitose

(Photo: S. Imboden, 20 November)

5. Syrup, Fondant, or Nectar

A translucent, oval droplet corresponds to nectar not yet transformed into honey and therefore not yet capped. These droplets may also correspond to feeding syrup or fondant. They must not be confused with condensation water, which forms more or less extensive puddles (see varroa monitoring board No. 10).

6. Activity of Wax-Producing Bees

Finding fragments of translucent wax scales indicates the activity of wax-producing bees. Comb-building activity is therefore under way and the colony's volume is developing progressively. Wax scales gradually take on a beige colour, then pale yellow, then increasingly dark brown as worker bees incorporate salivary solvents, pollen, and other hydrocarbon components. It should be recalled that wax gland production varies with the age of the worker. From the 12th day after emergence, wax production is at its maximum. It begins to decline from the 18th or 19th day of the worker's life, but remains possible until the end of the bee's life if required, for example at the resumption of egg laying in spring, when 6-day-old larvae need to be capped.

(Photo: Wolfhard S. Hüsken) Photos 10 & 11: Do not confuse sugar crystals (see photo 7) with wax debris (red circles). Wax moth frass (blue circles).

Photos 12, 13 & 13a: The bees want to build. In spring, this is a sign that the colony is developing. Allow foundation frames to be drawn out.

(Photo: S. Imboden, 20 November)

7. Pollen as a Protein Source

Pollen, to which bees add nectar, glandular secretions, and lactic acid bacteria, undergoes fermentation to form bee bread. The composition of bee bread is broadly similar to that of fresh pollen, but contains more essential compounds, bacteria, enzymes, and moulds (Guilliam, 1997). Its biological value is therefore superior.

Bee bread provides the colony with proteins, amino acids, fibre, lipids, vitamins, and minerals. It thus makes it possible to balance the bees' diet and prevent deficiencies (particularly in vitamins and minerals). A colony consumes between 12 and 40 kg of pollen per year. The qualitative aspect of pollens is very important insofar as the diversity of proteins brought to the hive is the determining factor.

8. Condensation Water

When the colony consumes its honey stores and converts glucose/fructose into energy, the chemical reactions consume oxygen (O²) and produce carbon dioxide (CO²) and water. Condensation of this water forms more or less extensive droplets that mix with the debris on the varroa monitoring board. Condensation water confirms that the colony is producing heat, either for itself (cluster) or to rear brood. If, in addition, entrance observation reveals pollen loads being brought in and water foragers are in full activity, brood rearing is very probably under way.

9. Food Shortage, Chilled Brood, or Wax Moth

Larval skins of coiled larvae or pupal fragments indicate food shortage (cannibalism) or a brood area too large relative to the number of nurse bees (the brood is chilling). Diseases or wax moth could also be the origin of these larvae or pupae.

• Check immediately whether there is sufficient food within the colony. If not, place a full food frame near the brood nest.
• Reduce the colony if the brood is chilling.

Photos 18, 19: Watch for signs of food shortage.

(Photo: S. Imboden, 20 November)

10. Propolis

Ochre-yellow, green-brown coloured droplets suggest propolis droplets used to seal cracks and openings in the hive. This complex material is produced by bees from certain plant resins obtained from conifers, but also from the buds of several species of alders, willows, birches, plum trees, ash trees, oaks, and elms, poplars (which appear to be the most important source), and chestnuts. After collection, bees incorporate wax and salivary enzymes. Propolis is also used by the colony to embalm a killed intruder (shrew/hawk moth…) and to maintain perfect hygiene thanks to its antiseptic properties.

(Photo: Wolfhard S. Hüsken)

Photo 20: Propolis is a complex material produced by bees from certain plant resins. Do not confuse it with bee faeces shown below.

11. Bee Faeces

If the varroa monitoring board shows one or two oval, inhomogeneous, brownish spots, these may be the droppings of a bee that had difficulty performing its cleansing flight due to unfavourable weather conditions. If, on the other hand, the board is smeared with faeces, the beekeeper will suspect nosema, a parasitic disease of bees caused by a parasite of the fungal class (formerly classified among the Protozoa). This pathology affects all three bee castes and is caused by the proliferation of Nosema apis or Nosema ceranae in the intestinal cells. The parasite may be present in non-pathogenic form in the colony (asymptomatic infestation) or become pathogenic (disease) under the influence of predisposing factors such as humidity, confinement, or rearing on melezitose stores.

The cycle is complex and varies according to environmental conditions. The parasite can be found in two forms corresponding to the two main phases of its cycle:

• Amoeboid stage: vegetative and reproductive phase of the parasite by cell division within the intestinal cells of the bee.
• Spore stage: passive resistance and dissemination phase.

When ingested by the bee (feeding, cleaning), the spores germinate in the midgut, where the environment is favourable to them. They then penetrate the cells of the gut wall via a polar tube that allows migration of the infecting material (sporoplasm) into the epithelial cell. Nosema sp. multiplies and grows. At the end of this development, the infected cell degenerates and is generally destroyed, releasing large quantities of spores that will reinfect other cells or be evacuated with the faeces, thus becoming an important source of contamination in the hive environment.

Spores can survive 5 to 6 weeks in bee carcasses, one year or more in faecal deposits, and 2 to 4 months in honey.

12. Eggs

When a few eggs are visible on the varroa monitoring board, the queen is laying. Normally an egg laid at the base of a cell does not end up on the board. The presence of numerous eggs could suggest a laying worker colony (several eggs per cell, some of which are displaced by workers), or possibly cannibalism of open brood following a cold snap… When egg laying resumes, stores must be monitored closely to ensure that fuel does not run short. In the event of a cold snap, capped brood is not normally abandoned and the heater bees will do everything possible to maintain a temperature of around 34–37°C for the survival of this particularly sensitive brood.

13. Capping Fragments

Capping fragments resembling small yellow/beige cups are detected when brood begins to emerge. It can be inferred that the queen has been laying for more than 3 weeks. Experienced observers will distinguish between worker brood cappings (smaller) and drone brood cappings (larger).

14. Brood Capping Debris and Food Cell Debris

The presence of debris resembling coarse breadcrumbs corresponds to brood capping debris that emerging bees cut with their mandibles. Debris resembling finer breadcrumbs comes from the uncapping of food storage cells by house bees.

Photo 29: Brood capping debris and/or food cell debris.

15. Chalkbrood

Chalkbrood is a fungal disease that affects worker and drone brood. The varroa monitoring board may also carry fragments of mummified larvae. Ascosphaerosis, also called "chalkbrood", is an infection of honey bee larvae by the fungus Ascosphaera apis. This fungus enters its host through spore ingestion, then develops in the gut before reaching the larval skin, which it covers with a white down; the larva eventually desiccates, takes on a mummy-like appearance, and crumbles with a chalky consistency, remaining white or turning black when sporulation occurs. The disease appears mainly in weak colonies; it is favoured by sharp temperature drops and high humidity. It can affect individual colonies or, in the case of bad weather conditions (cold, humidity), entire apiaries in epidemic form. A site regularly and massively affected by chalkbrood is considered unsuitable; hives should therefore be moved to a sunnier location. A heavy infestation can kill colonies.

16. Intruder: Varroa destructor

The presence of such a carpet of dead varroa mites beneath the colony must be correlated with any formic acid or oxalic acid treatment the beekeeper has just administered… If this drop is "natural" (more than 15 days after a treatment), the colony has little chance of survival unless an emergency oxalic acid treatment is carried out in the short term, after completely removing all brood.

To reproduce, the fertilised female varroa mite lodges in a cell ready to be capped. The foundress begins to lay 60 to 70 hours after capping, producing one egg every 30 hours — first a male, then females. Having reached sexual maturity, the brother will mate with his sisters as soon as they too are sexually mature. The foundress thus lays up to 5 eggs in worker brood and up to 6 eggs in drone brood. Upon emergence of the parasitised worker, the foundress plus 2–3 fertilised female varroa mites leave the cell. Upon emergence of the parasitised drone, the foundress plus 4–5 fertilised female varroa mites leave the cell. The male varroa mite, which is much lighter in colour than the female, dies after mating and therefore does not leave the cell alive. Mature but unfertilised females cannot produce offspring.

25% of varroa mites are found in the natural mite drop immediately after emergence of the adult bee (immature, unfertilised forms, grooming, etc.). A fertilised female varroa mite can complete several cycles; over the course of her life, a fertilised female varroa mite will give rise to an average of 2–6 fertilised female varroa mites. Under optimal conditions (no colony collapse/brood break/swarming), the varroa mite population doubles every 20–30 days.

The adult varroa mite has the form of a small, oval, red-orange cup, shiny on the dorsal surface and matt on the ventral surface. Looking carefully, one can distinguish its legs, which often protrude beyond the edge of its carapace. Careful examination of the varroa monitoring board makes it possible to identify lighter, even whitish, immature forms corresponding to sexually immature, hence unfertilised, mites that do not survive the emergence of the young bee.

17. Intruder: Mouse

The presence of numerous debris fragments of bee legs/wings and blackish-brown, slightly elongated but unstriated faecal fragments raises suspicion of a mouse that has taken up residence on the hive floor to spend the winter in the warm. It builds its nest there and coarse wood/straw debris can be found on the varroa monitoring board…

18. Intruder: Wax Moth

The discovery of black, more or less rectangular and striated debris comes from the larvae of the wax moth. While the adult moth does not feed, the caterpillar is an altogether different matter, whose voracity commands the biologist's attention. With its sharp mandibles, the larva devours everything in its path: residues on the base of brood cells, pollen, wax, honey, larvae, wood, polystyrene from mating nucleus boxes…

The caterpillar's rapid growth allows it to reach a size of several centimetres, doubling its weight every day for the first 10 days after hatching!

This incredible growth rate explains why the wax moth can destroy all the combs of a weakened hive in 10 to 15 days.

January Photos 39, 39a, 39b: A wax moth infestation is easily identified by the black droppings found on the varroa monitoring board.

(Photo: S. Imboden, 20 November)

(Photo: S. Imboden, 20 November)

19. Guests: Pseudoscorpions (Ellingsenius indicus)

Careful observation of the varroa monitoring board sometimes reveals unusual hive guests. In 1930, biologists discovered the presence of small arthropods living inside hives and feeding on various debris (dead bees, diseased brood, wax moth larvae, etc.). Arthropods are invertebrate animals with a rigid (chitinous) exoskeleton, a segmented body, and limbs or appendages composed of articulated elements that give them great freedom of movement. The inextensible carapace is regularly replaced during the animal's growth through successive moults.

Ellingsenius indicus is one of these pseudoscorpions belonging to the arachnids and therefore possessing 4 pairs of legs. It is equipped with a pair of pincers but has no sting and measures approximately 6–8 mm in length. It lives in Asia and cohabits familiarly with the local bee Apis cerana. Ellingsenius indicus is fond of varroa mites, which it devours by immobilising them with its pincers, plunging its mouthparts (chelicerae) beneath the chitin carapace and sucking the contents of the mite's body after injecting a liquefying fluid. This pseudoscorpion is completely harmless to the bee A. cerana, which even accepts being transported by it, fixed to the bee's thorax, from one corner of the hive to another. It contributes to keeping the infestation level low by devouring several dozen varroa mites per day.

20. Guests: Ants

Ants are closely related to bees not only in the classification of insects (order Hymenoptera) but in many aspects of their social organisation and communication methods. They benefit from the warmth of the hive, pilfer residues of sugary substances (honey, nectar, royal jelly), or feed on the debris and carcasses of their cousins, who tolerate them.

21. Guests: Pollen Mites

One can sometimes observe tiny oval organisms, much smaller than varroa mites, whitish in colour, bearing several legs (8), running at great speed across the varroa monitoring board covered in pollen/wax debris. These are pollen mites, completely harmless to bees, living in the colony's debris like true scavengers. The photo below makes it possible to compare the size of these mites relative to the red-circled varroa mite, directly next to the pollen pellet. Two immature varroa mites of beige colouration can also be noted in passing: the blue-circled one showing its dorsal surface and the other, yellow-circled, its ventral surface…

No action required.

22. Robbing

The discovery of numerous wing and leg fragments, etc. raises suspicion of robbing of a weak, diseased, and/or queenless colony through the intrusion of an unwanted guest into the hive (bees, wasps, shrews…).

See also:

• Practical Guide: 1.5.1 Measuring the natural mite drop
• Practical Guide: 4.8.2 Hive debris inspection
• Practical Guide 1.1: Varroa management plan