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 wintering is not desirable, even on a fine sunny day. The colony, which forms a cluster to minimize heat loss and optimize food consumption, should not be disturbed.
If disturbed, the cluster tends to break up. An increase in the cluster’s volume is associated with an increase in its surface area, and thus greater heat loss, and with increased oxygen exchange with the core of the cluster, which leads to increased heat production and fuel consumption. Opening the hive would unnecessarily cool the colony and would destroy the propolis bridges that ensure good sealing against draughts.
Observation at the entrance provides little information, because bees fly only rarely below 8–10°C. The landing board sometimes allows a small amount of condensation water to be found, which reassures the beekeeper: this physical phenomenon indicates that warm, humid air (produced by the colony) comes into contact with cold air (present in the hive or close to the entrance grid) or with a cold solid, for example the hive wall or the cover 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 everything is fine inside the hive…
We are therefore left with examination of the drawer. This removable device, located under the screened bottom of the brood box, collects debris produced by the colony. This debris passes through the floor grid due to the comings and goings of the workers and falls onto an oiled or unoiled insert, forming deposits parallel to the frames, sometimes interrupted by crosspieces of the hive floor.
The drawer is examined after being placed under the colony for 48–72 hours. Too often, the drawer is used only 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 trouble to examine it regularly, the observed elements, waste, fragments, and other residues provide valuable information about what is happening between the frames of the brood box where the colony is located. Examination of the drawer must always be correlated with the beekeeping calendar: a drawer inspected in summer will be very different from the same drawer opened at Christmas.
1. Colony strength and position
Visualization of “windrows” corresponds to the fall of debris from the spaces between frames. These windrows make it possible to locate the position of the colony and assess its strength. During winter, the cluster readily sits close to the hive wall warmed by sunlight, therefore often on the south side. Counting the windrows makes it possible to determine the number of frames between which the colony is grouped, and thus the approximate size of the cluster.
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Photo 1: Windrows help locate the position of the colony and assess its strength. A strong colony has at |
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The debris bands indicate the volume and position of the winter cluster. As spring approaches, brood expands. If colony development then stagnates or even regresses, the beekeeper will examine the brood carefully in search of a clear cause. Examination of the queen is also essential to check her age (decline in laying) or a possible supersedure followed by incomplete, or even absent, mating (virgin queen).
- No action required
- If the colony remains roughly the same size or becomes smaller, this may indicate a brood or queen problem.
2. Worker activity
Closer observation of the debris present in the windrows provides valuable information about worker activity. Dark brown fragments correspond to uncapping of honey stores: the colony consumes fuel so that the core of the cluster can heat the queen, any very limited brood, and the peripheral layers of the cluster mantle, whose temperature must not drop below 6°C. Recall that below 6°C, bees become torpid and eventually die from cold.
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Photo 2: The dark brown (older) and light brown (more recent) fragments correspond to uncapping of honey stores. |
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Photo 3: White crumbs: the bees are starting to tap into the winter stores. Crystallized sugar, which the colony could not consume due to lack of water, falls onto the board.
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3. Bottom board difficult to interpret
This bottom board is difficult to interpret because it was in place for several days, or even weeks. The debris deposits are too thick to yield reliable indications about colony health. The dark brown central windrows correspond to uncapping of old capped stores. Lighter-colored windrows correspond to uncapping of more recent stores. One may think the colony changed position according to the location of the stores, because it is unlikely that it occupies 10 full frames (11 windrows)… A little mold at the bottom of the photo indicates condensation above the entrance grid.
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Photo 4: A drawer that is not renewed regularly is difficult to interpret. Rule: leave the drawer in place for max. 1–5 days |
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Photos 5&6: Light wax crumbs: opening of capped food (new combs)
Brown wax crumbs: colony is producing brood
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4. Type of food
The small translucent crystals, reminiscent of crystallized sugar and sweet-tasting if placed on the tongue, result from consumption of syrup/candy.
The white microcrystals (lower image), resembling flour and without a sweet taste, correspond to consumption of melezitose or possibly another highly crystallized sugar that requires a lot of energy to dissolve (hard-set honey, for example ivy honey).
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(Photo: S. Imboden, 30 December)
Photos 7, 8, 8b (S. Imboden, 22 December): It is possible to determine the type of sugar:
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 (Photo: S. Imboden, 20 November) |
5. Syrup, candy, or nectar
A translucent, oval droplet corresponds to nectar not yet transformed into honey and therefore not capped. These droplets may also correspond to feeding syrup or candy. They should not be confused with condensation water, which forms more or less extensive puddles (see drawer no. 10).
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Photo 9: A translucent, oval droplet corresponds to nectar not yet transformed into honey, feeding syrup, or candy. |
Late December 6. Activity of wax-producing bees
Finding translucent wax fragments indicates activity of wax-producing bees. Comb construction is therefore under way, and colony volume is gradually increasing. The wax gradually turns beige, pale yellow, and then increasingly dark brown as worker builders incorporate salivary secretions, pollen, and other hydrocarbon components. Recall that wax gland output varies with the worker’s age. From the 12th day after emergence, wax production is maximal. It begins to decrease from the 18th or 19th day of the worker’s life, but remains possible until the end of the bee’s life if needed, for example when egg laying resumes in spring, when 6-day-old larvae must be capped.
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Photos 10&11: Do not confuse sugar crystals (see photo 7) with wax crystals (red circles). |
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Photos 12, 13 & 13a: The bees want to build. In spring, this is a sign that the colony is developing.
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 (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 the latter contains more essential compounds, bacteria, enzymes, and molds (Guilliam, 1997). Its biological value is therefore higher.
Bee bread provides the colony with proteins, amino acids, fiber, lipids, vitamins, and minerals. It thus helps balance the bees’ diet and prevent deficiencies (especially in vitamins and minerals). A colony consumes between 12 and 40 kg of pollen per year. The qualitative aspect of pollens is very important, since it is the diversity of proteins brought into the hive that is decisive.
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Photo 14: Pollen on the landing board suggests that the queen is laying |
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Photo 15: The colony has already produced a lot of brood and is storing pollen.
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8. Condensation water
When the colony consumes 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 debris on the drawer. Condensation water confirms that the colony is producing heat, either for itself (cluster) or to rear brood. If, in addition, observation at the entrance reveals pollen intake and water carriers are highly active, brood rearing is very probably under way.
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Photo 16: When nights are still cold, condensation water indicates that brood rearing is very probably under way. |
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Photo 17: The colony is probably maintaining brood and needs approx. 1 kg of food per week.
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9. Food shortage, chilled brood, or wax moth
Curled larval skins or pieces of pupae indicate that there is a food shortage (cannibalism) or that the brood area is too large relative to the number of nurse bees (the brood is chilled). Diseases or wax moth could also be the cause of these larvae or pupae.
- Immediately check whether there is enough food within the colony. If not, place a full food frame close to the brood nest.
- Reduce the colony if brood is chilled.
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Photos 18, 19: Watch for signs of food shortage |
 (Photo: S. Imboden, 20 November) |
10. Propolis
Yellow-ochre–green–brown colored droplets suggest drops of propolis used to seal cracks/openings in the hive. This complex material is made by bees from certain plant resins from conifers, but also from the buds of several species of alders, willows, birches, plums, ashes, oaks, and elms, poplars (which appear to be the most important source), and horse 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.
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Photo 20: Propolis is a complex material made by bees from certain plant resins. Do not confuse it with the bee droppings below |
11. Bee droppings
If the drawer shows one or two oval, inhomogeneous brownish spots, this may be a dropping from a bee that had difficulty taking its cleansing flight due to unfavorable weather conditions. By contrast, if the board is smeared with droppings, the beekeeper will consider nosemosis, a parasitic disease of the bee caused by a parasite of the class Fongids (formerly classified among Protozoa). This pathology affects all three bee castes and is due to proliferation of Nosema apis or Nosema ceranae in the intestinal cells. The parasite may be present in a non-pathogenic form in the colony (asymptomatic infection), or become pathogenic (disease) mainly under the influence of predisposing factors such as humidity, confinement, wintering on melezitose...
The cycle is complex and varies with environmental conditions. The parasite may occur in two forms corresponding to the two main phases of its cycle:
- Amoeboid morphology stage: vegetative and reproductive phase of the parasite by cell division in the bee’s intestinal cells.
- Spore stage: passive and resistant phase, but also the phase of dissemination.
When ingested by the bee (feeding, cleaning), the spores germinate in the midgut where the environment is favorable. They then penetrate the wall cells thanks to a polar filament 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, which releases large quantities of spores that will reinfect other cells or be expelled with droppings, thus becoming an important source of contamination in the hive environment.
The spores can survive 5 to 6 weeks in dead bees, a year or more in droppings, and 2 to 4 months in honey.
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Photo 21: If the board is smeared with droppings, the beekeeper will consider nosemosis, a parasitic disease of the bee |
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Photo 22&23: Bee droppings (yellow-brown) may be a sign of disease or stress (e.g., varroa treatment). Bee diarrhea is most often caused by dysentery or Nosema. Dysentery is a non-contagious intestinal disorder that occurs mainly in winter. Wintering-related problems are the cause of this diarrhea. It is triggered in particular by forest-honey stores or by stress such as lack of air or disturbance of winter rest. Dysentery caused by amoebae is contagious. Nosema is a fungal disease that can occur under the influence of two different pathogens: Nosema apis and Nosema ceranae. New spores are transmitted via droppings.
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12. Eggs
If a few eggs are visible on the drawer, the queen is laying. Normally, an egg laid at the bottom of a cell does not end up on the drawer. The presence of many eggs could suggest a drone-laying situation (several eggs per cell, some of which are moved by workers), possibly cannibalism of open brood after a cold snap... When laying resumes, stores must be monitored closely to ensure fuel does not run out. In the event of a possible return of cold weather, sealed brood is not usually abandoned, and heater bees will do everything possible to maintain a temperature on the order of 34–37°C for the survival of this particularly sensitive brood.
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Photo 24: If a few eggs are visible on the drawer, the queen is laying. |
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Photo 25: The presence of many eggs could suggest a drone-laying situation (several eggs per cell, sometimes removed by cleaning workers), possibly cannibalism of open brood after a cold snap... A drone-laying colony has no future. It can rear only males, either because its queen has lost the ability to fertilize the eggs she lays, or because there is no queen at all and laying workers have taken over.
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January 13. Capping fragments
Capping fragments resembling yellow/beige cups are detected when brood begins to emerge. One can infer that the queen has been laying for more than 3 weeks. Experienced observers can distinguish between worker-brood cappings (smaller) and drone-brood cappings (larger).
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Photo 26: Capping fragments are detected when brood begins to emerge. |
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Photo 27: Many large capping fragments in spring may indicate that drones are emerging in large numbers and will be sexually mature in two weeks. This would therefore mark the start of swarming. But it can also indicate that the colony is drone-laying.
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Photo 27a: Even in late November, capping fragments can be found (right corner) |
Late November 
14. Debris from brood cappings and food cells
Debris resembling coarse breadcrumbs corresponds to fragments of brood cappings cut with the mandibles by emerging bees. Debris resembling finer breadcrumbs results from uncapping of food-storage cells by store bees.
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Photo 28: Coarse capping debris indicates emergence of young bees. Finer debris comes from the cells of food stores. |
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Photo 29: Debris from brood cappings and/or from food-store cells.
15. Chalkbrood
Chalkbrood is a fungal disease affecting worker and drone brood. The drawer may also be loaded with fragments of mummified larvae. Ascosphaerosis, also called “chalkbrood,” is an infection of honey-bee larvae by the fungus Ascosphaera apis. It enters its host through ingestion of spores, then develops in the gut before reaching the larval skin, which it covers with a white fuzz and which eventually dries out, giving the larva a mummy-like appearance; it then crumbles with a chalk-like consistency, remaining white or turning black in the case of sporulation. The disease occurs mainly in weak colonies; it is favored by sharp temperature drops and high humidity. It can affect individual colonies or, under poor weather conditions (cold, humidity), entire apiaries as an epidemic. A site that is regularly and severely affected by chalkbrood is considered unsuitable; the hives should therefore be moved to a sunnier location. Heavy infestation can kill colonies.
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Photo 30: Early in the morning, mummies lie on the hive floor and the landing board, most often in spring due to cold snaps and poor nutritional intake. Because of temperature, frames on the periphery are often the most affected. |
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Photos 31&32: The mummies change color as the fungus develops. First white, they become gray, then black when filaments form sporophores. In the case of heavy infestation:
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Early March 
16. Intruder: Varroa destructor
The presence of such a carpet of dead varroa mites under the colony must be related to a possible treatment with formic or oxalic acid that 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 fully removing brood.
To reproduce, the fertilized female varroa enters a cell that is ready to be capped. The foundress begins laying eggs 60 to 70 hours after capping, at a rate of one egg every 30 hours, first a male and then females. After reaching sexual maturity, the brother fertilizes his sisters, as soon as they are sexually mature as well. The foundress thus lays up to 5 eggs in worker brood and up to 6 eggs in drone brood. When the parasitized worker emerges, the foundress + 2–3 fertilized female varroa leave the cell. When the parasitized drone emerges, the foundress + 4–5 fertilized female varroa leave the cell. The male varroa, which is much lighter in color than the female, dies after mating and therefore does not leave the cell alive. Mature but unfertilized females cannot produce offspring.
Twenty-five percent of varroa mites are found in immediate natural drops after emergence of the imago (immature forms, unfertilized, grooming, etc.). A fertilized female varroa can complete several cycles; over her lifetime, a fertilized female gives birth to an average of 2–6 fertilized female varroa. Under optimal conditions (no collapse/laying interruption/swarming), the varroa population doubles every 20–30 days.
The adult varroa has the shape of a small, oval reddish-orange cup, shiny dorsally and matte ventrally. Looking closely, one can see its legs, which often protrude beyond the edge of its carapace. Careful examination of the drawer makes it possible to identify paler, even whitish, immature forms corresponding to sexually immature, and therefore unfertilized, mites that do not survive emergence of the young bee.
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Photo 33: 25% of varroa mites are found in immediate natural drops after emergence of the imago. |
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Photo 34: Threshold values for natural varroa drop and appropriate actions:
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17. Intruder: Mouse
The presence of numerous fragments of bees’ legs/wings and blackish fecal fragments, somewhat elongated but without ridges, suggests the presence of a mouse that has taken up residence at the bottom of the hive to spend the winter in the warmth. It builds its nest there and coarse fragments of wood/straw can be found on the drawer…
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Photo 35: The presence of numerous fragments of bees’ legs/wings and blackish fecal fragments, somewhat elongated but without ridges, suggests the presence of a mouse. |
Photo 36: Mouse droppings can also appear lighter. |
May 
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Photo 37: The debris bands indicate the importance and location of the winter seat. As spring approaches, brood expands.
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Photo 38: The shrew is very small and can enter through small openings. |
18. Intruder: Wax moth
Black debris, more or less rectangular and ridged, comes from wax moth larvae. While the adult moth does not feed, the caterpillar is quite different, and its voracity is striking. With its sharp mandibles, the larva devours everything in its path: residues at the bottom of brood cells, pollen, wax, honey, larvae, wood, polystyrene from mating nucs…
The caterpillar’s rapid growth allows it to reach several cm in size, doubling its weight each day during the first 10 days after hatching!
This incredible growth rate explains why wax moth can destroy all the combs of a weakened colony in 10 to 15 days.
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Photos 39, 39a, 39b: A wax moth infestation is easily identified by the black droppings found on the drawer. |
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 (Photo: S. Imboden, 20 November) |
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Photo 41: In addition, observing several uncapped cells surrounded by a rim (bald brood) and/or aligned linearly (tubular brood) indicates the presence of a gallery dug deep by wax moth. Freeze food combs at -18°C for two days, then store them in tightly sealed boxes Melt or destroy combs with silk immediately Acetic acid at 60–80% kills especially the eggs and the adult wax moth |
19. Guests: Pseudoscorpions (Ellingsenius indicus)
Careful examination of the drawer sometimes reveals unusual hive guests. In 1930, biologists discovered 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 growth by successive molts.
Ellingsenius indicus is one of these pseudoscorpions; it belongs to the arachnids and therefore has 4 pairs of legs. It has a pair of pincers but no sting and measures about 6–8 mm in length. It lives in Asia and cohabits closely with the local bee Apis cerana. Ellingsenius indicus feeds readily on varroa mites, which it immobilizes with its pincers, inserting its mandibles (chelicerae) under the chitin carapace and sucking out the interior of the mite’s body after injecting a liquefying fluid. This pseudoscorpion is completely harmless to the bee A. cerana, which even accepts transporting it, attached to its thorax, from one part of the hive to another. It helps maintain a low infestation level by consuming several dozen varroa mites per day.
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Photo 43: The pseudoscorpion is an extremely rare guest. It cannot keep varroa in check, but rejoice nevertheless at its presence. |
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Photo 44: Ellingsenius indicus feeds readily on varroa mites (4–6 varroa per day) by immobilizing them with its pincers.
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20. Guests: Ants
Ants are very close to bees not only in insect classification (order Hymenoptera) but also in many aspects of their social organization and communication. They benefit from the warmth of the hive, steal residues of sweet substances (honey, nectar, royal jelly), or feed on debris and carcasses of their cousins, who tolerate them.
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Photo 45: A colony in excellent condition has nothing to fear from ants.
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21. Guests: pollen mites
One can sometimes observe tiny oval organisms, much smaller than varroa mites, whitish in color, with several legs (8), running very fast on the drawer covered with pollen/wax debris. These are pollen mites, completely harmless to bees, living in the colony’s debris like true scavengers. The photo below allows comparison of the size of these mites with the varroa circled in red, right next to the pollen pellet. Note in passing two immature varroa mites with beige coloration: the one circled in blue shows its dorsal side and the other, circled in yellow, its ventral side...
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Photos 46, 47 & 46a: Pollen mites are completely harmless to bees and live in the colony’s debris. |
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22. Robbing
Finding numerous fragments of wings, legs, etc. suggests robbing of a weak, diseased, and/or queenless colony, triggered by the intrusion of an undesirable guest into the hive (bees, wasps, shrew...).
