Sealed Brood Cells Research Articles

Development of a user-friendly delivery method for the fungus Metarhizium anisopliae to control the ectoparasitic mite Varroa destructor in honey bee, Apis mellifera, colonies

A user-friendly method to deliver Metarhizium spores to honey bee colonies for control of Varroa mites was developed and tested. Patty blend formulations protected the fungal spores at brood nest temperatures and served as an improved delivery system of the fungus to bee hives. Field trials conducted in 2006 in Texas using freshly harvested spores indicated that patty blend formulations of 10 g of conidia per hive (applied twice) significantly reduced the numbers of mites per adult bee, mites in sealed brood cells, and residual mites at the end of the 47-day experimental period. Colony development in terms of adult bee populations and brood production also improved. Field trials conducted in 2007 in Florida using less virulent spores produced mixed results. Patty blends of 10 g of conidia per hive (applied twice) were less successful in significantly reducing the number of mites per adult bee. However, hive survivorship and colony strength were improved, and the numbers of residual mites were significantly reduced at the end of the 42-day experimental period. The overall results from 2003 to 2008 field trials indicated that it was critical to have fungal spores with good germination, pathogenicity and virulence. We determined that fungal spores (1 × 10(10) viable spores per gram) with 98% germination and high pathogenicity (95% mite mortality at day 7) provided successful control of mite populations in established honey bee colonies at 10 g of conidia per hive (applied twice). Overall, microbial control of Varroa mite with M. anisopliae is feasible and could be a useful component of an integrated pest management program.

Small hive beetle (Aethina tumida) oviposition behaviour in sealed brood cells with notes on the removal of the cell contents by European honey bee (Apis mellifera)

Small hive beetle (Aethina tumida) oviposition behaviour in sealed brood cells with notes on the removal of the cell contents by European honey bee (Apis mellifera)

Small hive beetle (Aethina tumida) oviposition behaviour in sealed brood cells with notes on the removal of the cell contents by European honey bees (Apis mellifera)

SummarySmall hive beetles (Aethina tumida Murray) can lay eggs cryptically through the cappings of sealed bee brood cells. However, honey bees (Apis mellifera L.) can detect this activity and respond by removing cell cappings and contents (hygienic behaviour). We were interested in identifying conditions that regulate this syndrome of stimulus and response. Beetle oviposition rate (proportion of cells in which beetles perforate the capping and oviposit) into sealed brood cells was shown to be unaffected by a range of beetle densities created experimentally in caged sections of sealed brood. Oviposition rate was, however, increased when beetles had access to a sealed brood cell not only at the capping, but also along at least one side if the cell was next to an empty cell. Beetle oviposition rates into sealed brood cells were unaffected by the presence of Varroa destructor mites in the cell within a range of 1–4 mites per cell. The expression of hygienic behaviour toward beetle-perforated brood cells ranged from 10.6 77.2 % across colonies, but was unaffected by the colony strength parameters of bee population and cm2 brood.

Detection and removal of brood infested with eggs and larvae of small hive beetles (Aethina tumida Murray) by Russian honey bees

SummaryThe response of Russian honey bees to brood infested with small hive beetle (SHB) eggs and larvae was compared to that of a commercial stock (predominantly of A. m. ligustica). Test brood was grouped as follows: a) NoP = no perforation either of capping or cell wall; b) PWall = perforation of cell wall only; c) PCap = perforation of capping only; and d) PBoth = capping and cell wall perforations. All perforations were made by SHB. Our results showed that brood cells with perforations of the cell wall (PWall and PBoth) had the highest infestation (76.53 ± 2.10%) and number of eggs (58.46 ± 2.85 eggs). Because PCap showed low levels of infestation (29.17 ± 3.31% and 15.60 ± 1.31 eggs per infested cell), we calculated brood removal based on data from PWall and PBoth groups. Within 6 h, both stocks removed the contents of 39.24 ± 4.94% of PWall cells. A higher removal rate of 50.51 ± 5.80% was observed in PBoth cells. These two groups of brood had the highest numbers of eggs per infested cell (50–70 eggs). Eggs hatched after the 6 h observation and subsequent hygienic removal was of brood infested with larvae. At 20 h, additional 56.41 ± 4.62% (PWall) and 42.04 ± 4.91% (PBoth) removal rates were observed. Overall, the cumulative removal rates for both stocks were similar with means of 85.11 ± 2.98% and 84.32 ± 4.29% for the commercial and Russian honey bees, respectively. In conclusion, we observed that both honey bee stocks were able to detect eggs inside the sealed brood cells and remove them with the infested brood.

Social complexity in bees is not sufficient to explain lack of reversions to solitary living over long time scales

BackgroundThe major lineages of eusocial insects, the ants, termites, stingless bees, honeybees and vespid wasps, all have ancient origins (≥ 65 mya) with no reversions to solitary behaviour. This has prompted the notion of a 'point of no return' whereby the evolutionary elaboration and integration of behavioural, genetic and morphological traits over a very long period of time leads to a situation where reversion to solitary living is no longer an evolutionary option.ResultsWe show that in another group of social insects, the allodapine bees, there was a single origin of sociality > 40 mya. We also provide data on the biology of a key allodapine species, Halterapis nigrinervis, showing that it is truly social. H. nigrinervis was thought to be the only allodapine that was not social, and our findings therefore indicate that there have been no losses of sociality among extant allodapine clades. Allodapine colony sizes rarely exceed 10 females per nest and all females in virtually all species are capable of nesting and reproducing independently, so these bees clearly do not fit the 'point of no return' concept.ConclusionWe argue that allodapine sociality has been maintained by ecological constraints and the benefits of alloparental care, as opposed to behavioural, genetic or morphological constraints to independent living. Allodapine brood are highly vulnerable to predation because they are progressively reared in an open nest (not in sealed brood cells), which provides potentially large benefits for alloparental care and incentives for reproductives to tolerate potential alloparents. We argue that similar vulnerabilities may also help explain the lack of reversions to solitary living in other taxa with ancient social origins.

Formic acid fumigator for controlling varroa mites in honey bee hives

The 50% formic acid fumigator (FAF) for varroa mite control was developed as part of a SARE grant (1999–2001). The fumigator was evaluated for five years on 123 colonies in five bee yards in Connecticut, Maryland and West Virginia (USA). Treatments eliminated all mites on adult bees and 90–95% of mites in sealed brood cells. Very few brood or new young adult bees were injured by the treatment. The fumigator is a simple design and the overall cost of treatment is about $1.00 per hive, or less. The 50% FAF was less toxic to bees compared to other treatments using 65%, 80% or 90% formic acid. The fumigator was applied for 18–24 hours when ambient temperatures were between 15–30°C. In the USA, one treatment in mid-August to mid-September was effective and usually all that was required each year. The 50% FAF used with other essential oil treatments including salt-grease patties with wintergreen, feeding 1:1 syrup with Honey-B-Healthy® (spearmint and lemongrass essential oils), and use of screened bottom boards, together provide a synergistic effect to keep mite numbers at a relatively low level, as part of an integrated pest management (IPM) system.

Distribution of Varroa destructor between swarms and colonies

SUMMARYBee colonies reproduce by colony division during swarming. In colonies infested by the parasitic mite, Varroa destructor, colony division will at the same time split the mite population between the swarms and the remaining parent colonies. The present investigation compares infestation of swarms with that of parent colonies. We found that an average of 25 ± 9% of mites left the colonies with natural swarms, while 75 ± 9% remained in parent colonies of which 39 ± 11% were on bees and 36 ± 10% were within sealed brood cells. The relative swarm infestation did not differ from that of the remaining parent colony in this study, but very low proportions of mites within sealed worker brood and a clear negative correlation to the proportion of mites in sealed brood strongly suggest that swarm infestation is asymmetric and lower than that of the remaining colonies.

Hot bees in empty broodnest cells: heating from within

Honeybee colonies maintain brood nest temperatures of 33-36 degrees C. We investigated brood nest thermoregulation at the level of individual worker behaviour and the transfer of heat from workers to the brood. Worker bees contribute to the regulation of brood nest temperature by producing heat while sitting motionless on the caps of brood cells. We report here an additional, newly observed heating strategy where heating bees enter empty cells between sealed brood cells and remain there motionless for periods of up to 45 min. Individually marked worker bees on the surface of sealed brood cells maintained thorax temperatures (T(th)) between 32.2+/-1.0 degrees C and 38.1+/-2.5 degrees C (mean +/- S.D.; N=20 bees) with alternating warming and cooling periods. Most of the observed bees made one or several long-duration visits (>2 min) to empty cells within the sealed brood area. T(th) at the time bees entered a cell [T(th(entry))] was 34.1-42.5 degrees C (N=40). In 83% of these cell visits, T(th(entry)) was higher (up to 5.9 degrees C; mean 2.5+/-1.5 degrees C; N=33) than the mean T(th) of the same bee. High values of T(th(entry)) resulted from preceding heating activity on the comb surface and from warm-ups just prior to cell visits during which T(th) increased by up to +9.6 degrees C. Bees inside empty cells had mean T(th) values of 32.7+/-0.1 degrees C (resting bees) to 40.6+/-0.7 degrees C (heat-producing bees) during long-duration cell visits without performing any visible work. Heating behaviour inside cells resembles heating behaviour on the brood cap surface in that the bees appear to be inactive, but repeated warmings and coolings occur and T(th) does not fall below the optimum brood temperature. Bees staying still inside empty cells for several minutes have previously been considered to be 'resting bees'. We find, however, that the heating bees can be distinguished from the resting bees not only by their higher body temperatures but also by the continuous, rapid respiratory movements of their abdomens. By contrast, abdominal pumping movements in resting bees are discontinuous and interrupted by long pauses. Heat transfer to the brood from individual bees on the comb surface and from bees inside empty cells was simulated under controlled conditions. Heating on the comb surface causes a strong superficial warming of the brood cap by up to 3 degrees C within 30 min. Heat transfer is 1.9-2.6 times more efficient when the thorax is in touch with the brood cap than when it is not. Heating inside empty cells raises the brood temperature of adjacent cells by up to 2.5 degrees C within 30 min. Heat flow through the comb was detectable up to three brood cells away from the heated thorax.

CLIMATE CONTROL, BEE STYLE

Whatever the weather, no self-respecting hive lets the temperature drop inside; the future of the next generation depends on it. If the hive's temperature falls a few degrees below 35°C, the incubating young's development is seriously threatened. Marco Kleinhenz explains that much of the hive's heat derives from general hive-keeping activity, but workers also help raise the temperature by congregating at the brood and vibrating their thoracic muscles to warm the incubating young. But how each individual worker contributes to the heating sum wasn't clear. Brigitte Bujok had noticed that some of the workers appear to position themselves over an incubating brood cell and press their thoraxes against the sealing caps `leaving a hot spot behind' explains Kleinhenz. But not much more was known about the brood's central heating strategy until Kleinhenz and Bujok teamed up with Stefan Fuchs and Jürgen Tautz to take a closer look at the heating bee's activity (p. 4217).Setting up a series of hives where they could monitor the bee's brood heating antics, Kleinhenz and his colleauges recorded individual's body temperatures with an infrared camera, and watched their behaviour. Some of the workers were happy to stay completely motionless on a brood cap for several minutes, pressing their thoraxes against the cap to warm the young within. But many of the bees preferred to find an empty cell amongst sealed brood cells,and take up residence, sometimes for over an hour. Kleinhenz explains that this apparently lazy behaviour had been noticed before, so he suspected that the bees were simply taking a rest; until he looked at their temperature. They were warming themselves before they vanished inside, and some bees emerged even warmer than when they went in! Were the bees really taking a nap, or were they taking up residence in an empty cell to warm the adjacent pupae?The team built a close observation hive where they could monitor bees'thoracic temperatures as they hunkered down in vacant cells. This time it was clear. Far from easing off and taking a rest, closeted bees were vibrating their thoracic muscles and reaching temperatures up to 41°C. Far from being idle, the workers were warming the brood.But how effective is the bee's novel heating strategy? Fitting a small resistor inside a bee's thorax, the team placed the simulated bee heater inside a cell, and recorded the temperature in adjacent cells. After 30 minutes, the heater bee's effect could be felt three chambers away. Kleinhenz also realised that once in place, a hot worker makes the most of its heat,warming all six of the surrounding cells, while usually a single occupant is the only beneficiary from a worker perched above it on the comb. What is more,the heater bees aren't profligate with their valuable resource, staying cool when surrounded by honey or vacant brood cells that don't require warmth, or when the brood is already warm enough.Kleinhenz also noticed that this dedicated band of bees also take great care not to over-heat their precious charges. They monitor the brood cells'temperatures and ensure a comfortable clime for all, by never letting the hive rise above 35.9°C.

Ultrastructure and bacterial infection of wounds in honey bee ( Apis mellifera) pupae punctured by Varroa mites.

The damage to western honey bee, Apis mellifera, colonies caused by the originally Asian ectoparasitic mite Varroa destructor is mainly a consequence of the infestation of host bee pupae. In the capped brood cell, female mites puncture the host's integument at preferred sites in order to suck haemolymph. Due to repeated feeding by the mother mite and her progeny, these perforations are kept open until shortly before the imaginal moult of the bee. Thereafter scarring takes place, thus preventing microbial infection after the adult bee has emerged from the protected environment of the sealed brood cell. However, colonies of various bacteria were found in the open wounds of about 15-30% of all inspected host pupae with an abundance depended on the level of host brood cell infestation by the mite. The small punctures of the pupal integument are difficult to detect but, by vital staining with trypan blue, the wounds can be visualised. The ultrastructure of the pupal wounds, the bacterial colonies and the scarring process are documented by a series of scanning electron micrographs.

Potential mechanism for detection by Apis mellifera of the parasitic mite Varroa destructor inside sealed brood cells

Abstract The parasitic mite Varroa destructor Anderson & Trueman is a major pest of the honeybee Apis mellifera L. throughout the world. Chemical agents currently used for mite control leave contaminating residues and promote pesticide resistance. As an alternative means of control, it would be useful to identify natural substances enabling bees to detect Varroa inside brood cells. These substances could then be used to trigger mite hygienic behaviour by bees.In this study several techniques were used to screen substances that might allow detection of infested brood cells by bees. Gas chromatography‐mass spectrometry analysis was performed on substances extracted in dichloromethane from the contents of brood cells. Solid phase microextraction and solid injection were performed on substances obtained from living and dead Varroa, respectively. Electroantennography was performed to assess the sensitivity of olfactory receptors in bee antennae to some of these substances.Principal component analysis based on proportions of cuticular substances allowed discrimination between bees and other cell contents. Foundress Varroa exhibited the greatest dissimilarity to healthy pupae that were used as controls. Immature Varroa and faecal material were intermediate. High molecular weight compounds, mainly dimethylalkanes, were proportionally the most characteristic components of foundress Varroa. This finding suggests that these compounds would be the most apt to induce uncapping of cells infested by Varroa. Solid‐phase microextraction and solid injection demonstrated the presence of aliphatic acids, esters, and one alcohol, eicosenol, in Varroa. Electroantennographic recordings showed that mite‐resistant bees were more responsive to some acids and one ester. We speculate that these compounds may be involved in recognition of living Varroa by honeybees.

Mites from debris and sealed brood cells of Apis dorsata colonies in Sabah (Borneo) Malaysia, including a new haplotype of Varroa jacobsoni

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Reproduction of Varroa destructor in worker brood of Africanized honey bees (Apis mellifera).

Reproduction and population growth of Varroa destructor was studied in ten naturally infested, Africanized honey bee (AHB) (Apis mellifera) colonies in Yucatan, Mexico. Between February 1997 and January 1998 monthly records of the amount of pollen, honey, sealed worker and drone brood were recorded. In addition, mite infestation levels of adult bees and worker brood and the fecundity of the mites reproducing in worker cells were determined. The mean number of sealed worker brood cells (10,070 +/- 1,790) remained fairly constant over the experimental period in each colony. However, the presence and amount of sealed drone brood was very variable. One colony had drone brood for 10 months and another for only 1 month. Both the mean infestation level of worker brood (18.1 +/- 8.4%) and adult bees (3.5 +/- 1.3%) remained fairly constant over the study period and did not increase rapidly as is normally observed in European honey bees. In fact, the estimated mean number of mites fell from 3,500 in February 1997 to 2,380 in January 1998. In May 2000 the mean mite population in the study colonies was still only 1,821 mites. The fertility level of mites in this study was much higher (83-96%) than in AHB in Brazil (25-57%). and similar to that found in EHB (76-94%). Mite fertility remained high throughout the entire study and was not influenced by the amount of pollen, honey or worker brood in the colonies.

Africanized honey bees (Apis mellifera L.) are more efficient at removing worker brood artificially infested with the parasitic mite Varroa jacobsoni Oudemans than are Italian bees or Italian/Africanized hybrids

Africanized honey bees are more tolerant of infestations with the mite Varroa jacobsoni than are honey bees of European origin. The capacity of these bees to detect and react to brood infested with this mite could be one of the factors determining this tolerance. We tested colonies of Africanized bees headed by queens from swarms collected in Ribeirão Preto, São Paulo State. The Italian colonies had queens imported directly from the USA, or from the Brazilian Island of Fernando de Noronha, where varroa-infested Italian colonies have been maintained, untreated, since 1984. Recently sealed worker brood cells were artificially infested by opening the cell capping, inserting live adult female mites and resealing the cells. Control cells were treated in the same way, but without introducing mites. The ability of the Africanized honey bees to recognize and remove this artificially infested brood was compared with that of first generation Italian/Africanized hybrid bees, and with the two groups of "pure" Italian bees, in three separate experiments. Africanized colonies removed a mean of 51% of the infested brood, while Italian/Africanized hybrid colonies removed 25%. Africanized colonies also removed a significantly greater proportion of infested brood than did Italian colonies, headed by queens from the USA (59 vs. 31%, respectively). Similarly, when Africanized colonies were compared with colonies of Italian bees from Fernando de Noronha, the former were found to be significantly more efficient at removing infested brood (61 vs. 35%, respectively), even though the population of Italian bees on this island has been exposed to and survived varroa infestations (without treatment) for more than 12 years. Only the Africanized honey bees removed a significant proportion of varroa-infested brood, when the data was corrected for brood removal from control cells.

Juvenile mortality of the female descendants in the ectoparasitic mite Varroa jacobsoni in worker brood of Apis mellifera

SUMMARYDuring the autumn of 1996 and 1997 in Thessaloniki (Greece) juvenile mortality (JM) of the mite Varroa jacobsoni was studied in worker brood cells of frozen combs from 21 Apis mellifera macedonica colonies. The infestation level of the colonies varied between 8% and 35%. Sealed brood cells (n = 8454) containing a healthy worker pupa older than the ‘pale eyes’ stage or a resting adult were examined. The cells examined were singly infested by a fertile V. jacobsoni with normal offspring in 92% of the cases. A total number of 3543 developing fertile V. jacobsoni female descendants (fd) was studied. During the mobile phases the losses of the parasite in the first, second and third fd were 2.8%, 13.8%, 30.4%, respectively. Under natural conditions no death factors act against the first fd until it reaches the second immobile phase, or deutochrysalis phase (DCHR) in the worker brood cell. For the subsequent fd, malnutrition possibly plays the most important role during the pre-DCHR mobile phases. During the immobile phases the main losses of the first fd occur in the DCHR phase. On average, the death rates for the first, second and third DCHR were 6.2%, 11.3% and 14.2%, respectively, in worker brood cells containing maturing pupae. Rates of losses for the DCHR of the three fd determined in cells containing the resting adult were 15.8%, 37.1% and 56.9%, respectively. The general losses concerning all developing phases of the mite, i.e. pre-DCHR and DCHR, for the first, second and third fd in worker brood cells were 18.6%, 50.9% and 87.3%, respectively. Death of the DCHR of V jacobsoni in the worker brood cell of A. mellifera is connected with aging of the host. This is based on the following: (a), practically no death of DCHR was observed as long as the host retained its white body colour; dead DCHR appeared first when the aging worker pupa acquired yellow body colour; and (b), the death rate of DCHR increases as the worker pupa becomes older. The possible influence of different natural or artificial factors causing death of female DCHR is discussed.

Effects of delayed acaricide treatment in honey bee colonies parasitized by Varroa jacobsoni and a late-season treatment threshold for the south-eastern USA

SUMMARYWe set up 72 colonies of honey bees (Apis mellifera) in the piedmont region of Georgia and South Carolina, USA (2 states × 6 apiaries per state × 6 colonies per apiary) in April 1995. Colonies were individually housed in single-chamber Langstroth hive bodies and one honey super, started with standard mail-order 0.9 kg (2lb) packages of bees containing small incipient populations of the parasitic mite Varroa jacobsoni, and managed optimally as for honey production. Within each state, each apiary was assigned one of the following treatments: (1) treatment with Apistan acaricide in June, (2) treatment in August, (3) treatment in October, or (4) no treatment By December, colony bee populations were optimum in August-treated apiaries. Month of treatment did not affect bee body weight. There were treatment by state interactions for number of sealed brood cells, colony mite populations, and percentage of brood cells with disease-like symptoms. Our data suggest that late-season acaricide treatments in first-year colonies in the south-eastern USA piedmont are justified at colony mite populations of 3172 ± 324, 300-bee ether roll mite levels of 15 ± 1.4, and overnight adhesive bottom board insert mite levels of 117 ± 15 in colonies with 24 808 ± 2245 bees and 1825 ± 327 cm2 sealed brood; these conditions occurred in mid-August Acaricide treatments in or before August may eliminate mite-associated brood pathology in the south-eastern USA. Bottom board inserts were more reliable predictors of colony mite populations compared to the ether roll method.

Number of reproductive cycles of Varroa jacobsoni in honey-bee (Apis mellifera) colonies

Very little data exists concerning the number of reproductive cycles performed by individual Varroa mites. To understand the population dynamics of the Varroa mite it is necessary to know the number of fertile female offspring each Varroa female produces during her lifetime. The lifetime reproduction capacity of the mite consists of the mean number of fertile female offspring produced during each reproductive cycle multiplied by the mean number of cell passages. This paper describes an experimental design to estimate the number of reproductive cycles where mites are transferred to new mite-free colonies for reproduction in sealed brood cells. The data presented suggests that the mean number of reproductive cycles performed by the individual female mite is larger than previously accepted. Under optimal conditions, the mean number of reproductive cycles by Varroa females is probably greater than 1.5 but less than 2. Furthermore, the results show that the reproductive success of Varroa females going into cells to reproduce is not influenced by previous brood cycles.

Non-reproducing Varroa jacobsoni Oud. in honey bee worker cells?status of mites or effect of brood cells?

The parasitic mite Varroa jacobsoni Oud. reproduces in sealed honey bee brood cells. Within worker cells a considerable fraction of the mites do not produce offspring. It is investigated whether variation in the ratio of cells without reproduction is caused by properties of the worker brood, or by the state of the mites entering cells. Pieces of brood comb were taken from colonies of 12 different bee lines and were placed simultaneously into highly infested colonies. Non-reproduction was independent of the origin of the brood pieces, indicating a minor role of a variation due to different brood origin. Between colonies used for infestation, however, it differed considerably. A comparison of the proportion of cells without reproduction when infested by one Varroa mite or when infested by two or three Varroa mites showed, that non-reproduction was mainly related to the state of the mites entering cells, and only to a minor degree to an influence of the brood cells. A high ratio of worker cells without reproduction was consistently reported in bee lines which survive the disease without treatment, and a high level of non-reproduction is thus regarded to be a key factor in breeding bees for high Varroa tolerance. The current results indicate, that differences in this trait are only to a minor degree related to differences between bee lines in the ability of the bee brood to induce oviposition. These differences seem rather to depend on other, unknown colony factors influencing the reproductive state of Varroa when they enter cells for reproduction.

Observations on the initiation and stimulation of oviposition of theVarroa mite

FemaleVarroa mites were collected from adult bees and were classified as swollen or not swollen. After introduction of these mites into recently sealed worker brood cells the average number of offspring of reproducing swollen mites was similar to that of naturally invaded mites, but the non-swollen mites produced a significantly lower number of offspring. This suggests that the oviposition of adult mites is stimulated by a preceding stay on adult bees. When (non-swollen) mites collected from brood cells were kept for 35 days in Eppendorf test tubes containing a larva or a pupa, their reproduction was similar to that of swollen mites.

The Symbiosis of Acarid Mites, Genus Ctenocolletacarus (Acarina, Acariformes), and Stenotritid Bees, Genus Ctenocolletes (Insecta, Hymenoptera)

Details of the life history of acarid mites of the genus Ctenocolletacarus have emerged from studies of nests of their hosts, Ctenocolletes albomarginatus and Ce. nicholsoni, and from rearing mites in the laboratory. The mites are closely associated with their hosts at all stages and their complete breeding cycle occurs in the hosts' sealed brood cells. Only the phoretic deutonymph leaves the cells. The mites, like their hosts, are univoltine. One to a few hypopi dismount from nesting females into each new brood cell and rapidly transform through non-mobile tritonymphs to adults of both sexes. Female mites oviposit on the ceiling of the cell during the host larva's early instars, giving rise to hundreds of larvae and then protonymphs by the time the host larva has completed feeding. Protonymphs metamorphose to hypopi once the host larva has defaecated and entered the prepupal phase. Hypopi remain with the dormant prepupa until the following season when they secrete themselves beneath the terga of the newly emerged adult bee. Circumstantial evidence, suggesting that hypopi are transmitted venereally between adult bees, is discussed. Adult, larval and protonymphal mites ingest pollen and the late protonymphal stage invades the faeces of the larval host. Sanitary control is a possible pay-off for the hosts.