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Honeybees have evolved a social immunity consisting of the cooperation of individuals to decrease disease in the hive. We identified a set of genes involved in this social immunity by analysing the brain transcriptome of highly varroa-hygienic bees, who efficiently detect and remove brood infected with the Varroa destructor mite. The function of these candidate genes does not seem to support a higher olfactory sensitivity in hygienic bees, as previously hypothesized. However, comparing their genomic profile with those from other behaviours suggests a link with brood care and the highly varroa-hygienic Africanized honeybees. These results represent a first step toward the identification of genes involved in social immunity and thus provide first insights into the evolution of social immunity.

Summary Mite resistance that we had earlier called suppression of mite reproduction (SMR) is a form of hygienic behaviour that we have named Varroa Sensitive Hygiene (VSH). With VSH, adult worker bees (Apis mellifera) disrupt the reproduction of parasitic mites (Varroa destructor) by removing mite infested bee pupae from their cells. This study determines which brood cells are targeted by bees with VSH and which are not, and describes the relationship between brood removal and the sudden prevalence of sterile mites. We produced 26 colonies with different levels of VSH by backcrossing 14 queens from a high line, H (100% expression of VSH), and 12 queens from a low line, L (no VSH), to drones produced by an HL (high × low) queen. Because each of the 26 queens was mated to one drone, the resulting colonies were expected to represent the complete range of variability (0 to 100% of the alleles for VSH). To estimate brood removal, we measured mite populations in capped worker brood that was 0 - 3 days postcapping and again 7 days later when the cohort was aged 7 - 10 days postcapping. We correlated removal of mite-infested brood with the relative presence (at 7 – 10 days postcapping) of three classes of foundress mites: (1) viable: those with at least one daughter that could mature before emergence of the host bee; (2) nonviable: those with progeny but with no daughters that could reach maturity; and (3) no eggs: those with dead or nonovipositing foundress mites. As the rate of removal increased, both classes 1 and 2 showed significant declines, whereas class 3 was unchanged. Therefore, oviposition of the mite or something associated with mite oviposition provides the stimulus for bees with the VSH trait to remove mite infested pupae.

SUMMARYThis study compared brood production, honey consumption (in winter only), population growth of honey bees (Apis mellifera), and population growth of parasitic mites (Varroa destructor) in hives with open screen or wood as floor material. Two experiments were conducted in Baton Rouge, Louisiana, USA, one in winter (19 colonies) and one in summer (22 colonies). In both experiments, we established uniform colonies of honey bees by subdividing 30 kg of mite-infested bees. Each colony began with about 11 000 bees, no brood, and uniform populations of mites (127 and 480 mites per colony in winter and summer, respectively). The summer test included a third treatment (8 colonies) where a wooden tray (5 cm deep) closed the space beneath a screen floor. After the first 20 days of the experiments, when no adult bees or mites had yet been produced in any of the colonies, the treatments showed no differences in brood production, honey consumption, or survival of adult bees. At nine weeks, colonies with screen f...

We measured significant variation in the instantaneous growth rates for varroa mites, Varroa destructor (Anderson & Trueman) from 1993 to 2002 in Baton Rouge, LA. Mite population growth was monitored in colonies of honey bees, Apis mellifera L., with queens from miscellaneous U.S. sources that had not been selectively bred for varroa resistance. Mite populations were measured at the beginning and end of short field tests that started in the late spring of each year. Analyses of multiple regression showed that only the first two of the following regressors were linear predictors of r, the instantaneous growth rate: 1) percentage of reproducing female mites, 2) proportion of total mites in capped brood, 3) mortality of mites in brood cells, 4) growth of the bee population, 5) capped brood area at the end of a test, and 6) duration of the test. Analysis of commonality indicated that the percentage of reproducing female mites explained ≈26% of the total variation in r, and the proportion of total mit...

This study demonstrated (1) that honey bees, Apis mellifera L, can express a high level of resistance to Varroa destructor Anderson & Trueman when bees were selected for only one resistant trait (suppression of mite reproduction); and (2) that a significant level of mite-resistance was retained when these queens were free-mated with unselected drones. The test compared the growth of mite populations in colonies of bees that each received one of the following queens: (1) resistant--queens selected for suppression of mite reproduction and artificially inseminated in Baton Rouge with drones from similarly selected stocks; (2) resistant x control--resistant queens, as above, produced and free-mated to unselected drones by one of four commercial queen producers; and (3) control--commercial queens chosen by the same four queen producers and free-mated as above. All colonies started the test with approximately 0.9 kg of bees that were naturally infested with approximately 650 mites. Colonies with resistant x control queens ended the 115-d test period with significantly fewer mites than did colonies with control queens. This suggests that beekeepers can derive immediate benefit from mite-resistant queens that have been free-mated to unselected drones. Moreover, the production and distribution of these free-mated queens from many commercial sources may be an effective way to insert beneficial genes into our commercial population of honey bees without losing the genetic diversity and the useful beekeeping characteristics of this population.

This study uses sibling analysis to measure the heritability in honey bees, Apis mellifera L., of characteristics that have been associated with resistance to the mite, Varroa jacobsoni Oudemans. Twenty-eight uniform colonies of bees were established on 13 May in Baton Rouge, LA, each with 1 kg of mite-infested bees and a queen. The 28 unrelated queens in these colonies were divided into 7 groups of 4 based on the insemination of 4 queens with the same mixture of semen from 1 of 7 sire colonies. After worker progeny from these queens had replaced the initial bee populations, a colony was related as a full sister to the other 3 colonies in its sire group and unrelated to the other 24 colonies. Heritability ( h 2) was 1.24 for proportion of mites in brood, 0.65 for hygienic behavior, 0.89 for the duration of the capped period, 0.46 for suppression of mite reproduction, and 0.00 for physical damage to mites (measured by the presence of physically broken or dented mites on the bottom board). These results suggest that it should be possible to enhance the expression of 4 of these 5 characteristics with selective breeding of bees, thus reinforcing confidence in our ability to breed honey bees for resistance to V. jacobsoni.

A breeding program for honey bees, Apis mellifera L., resistant to varroa mites, Varroa jacobsoni Oudemans, selected for bees that maintain low populations of mites with decreased reproduction. This study examines the causes for this suppressed mite reproduction. Nonreproductive mites were classified into 3 groups as follows: (1) mites that were alive but did not lay eggs, (2) mites that began laying eggs later than normal, and (3) mites that died before laying eggs (usually

Cet article examine les methodes de selection d'abeilles melliferes resistantes a l'acarien V. jacobsoni. Un plar. de selection est decrit ci-apres, qui devrait etre mis en œuvre dans tout programme de selection prenant en compte les caracteres des abeilles mesures au niveau de la colonie. 1) Developper des methodes pour mesurer les populations d'abeilles et d'acariens et pour mesurer les caracteres associes a la resistance. 2) Identifier les caracteres specifiques en relation avec la croissance des populations d'acariens. 3) Determiner si ces caracteres sont hereditaires. 4) Renforcer ces caracteres par un elevage selectif. 5) Regrouper les composantes de la resistance dans des abeilles productives et resistantes aux acariens. Dans cet article on entend par resistance a V. jacobsoni la selection chez les abeilles de caracteres qui vont retarder la croissance de la population d'acariens etablie dans la colonie. Lors du criblage initial des caracteres, nous avons utilise des reines fecondees par un seul mâle. Nous pensons que cela a permis de detecter aussi des caracteres peu frequents. Les caracteres au niveau de la colonie auraient pu etre caches si les reines avaient ete fecondees par plusieurs mâles. Notre approche decrit la croissance de la population d'acariens au sein d'une colonie d'abeilles par l'equation: P (ab)II = P 2 , ou P 1 et P 2 sont les populations initiale et finale d'acariens, a la variation de la population tant que les acariens sont dans les cellules de couvain, b la variation quand ils sont hors des cellules de couvain et n le nombre de cycles reproducteurs de l'acarien. L'equation est valable pour une colonie qui a un apport regulier en couvain d'ouvrieres de facon a permettre la reproduction de l'acarien. Seules les femelles adultes d'acariens sont comptees et toutes les mesures sont des moyennes pour la colonie. En comparant les taux de croisssance des populations d'acariens de chaque colonie (P 2 / P 1 ), on peut determiner la croissance reelle dans chaque colonie. Les valeurs a, b et n peuvent alors expliquer comment la population d'acariens est passee de P 1 , a P 2 en termes de composantes mesurables du cycle reproducteur de l'acarien. Les variations de la population d'acariens doivent se refleter dans une ou plusieurs de ces composantes. Les caracteres specifiques des abeilles (qui sont la base de la selection) peuvent alors etre associes a l'une de ces trois composantes. Quand plusieurs caracteres specifiques agissent sur une meme composante (par exemple, la suppresssion de la reproduction de l'acarien et le comportement hygienique), leur effet combine n'est pas necessairement additif ni benefique. Si en revanche un meme caractere specifique agit en meme temps sur differentes composantes, ceux-ci se combineraient probablement pour donner une colonie ayant une resistance accrue a V. jacobsoni. Jusqu'ici notre selection s'est concentree sur un caractere, la suppression de la reproduction de l'acarien, qui provoque la non reproduction des acariens qui penetrent dans les cellules de couvain. Sur la base de ce seul caractere hereditaire, nous avons produit des colonies dans lesquelles la population d'acariens decline durant une periode test de 70 j. Deux autres caracteres hereditaires, le comportement hygienique et la proportion d'acariens sur le couvain, peuvent avoir aussi une importance pour la selection d'abeilles resistantes.

The purposes of this study were to select honey bees, Apis Mellifera L., for resistance to varroa mites, Varroa jacobsoni Oudemans, and to find a probable cause for this resistance. As a genetic source, we assembled 8 colonies that we thought had potential for resistance to varroa. Queens and drones were propagated from this group to produce 43 instrumentally inseminated queens, each queen mated to only 1 drone. Colonies from 27 of these queens were tested in Louisiana and 16 were tested in Michigan. Each colony in the Louisiana test began with 986 ± 13 g (mean ± SD) of bees and =290 mites; Michigan colonies began with 3,212 ± 171 bees and =51 mites. The populations of mites and bees were measured 10 wk later. Three of the 43 colonies had fewer mites at the end of the test than at the beginning. During the experiment, we evaluated each colony for grooming behavior, hygienic behavior, the duration of the postcapping period, and the frequency of nonreproducing mites in brood cells. of these 4 characteristics, only nonreproduction of mites was highly related to a change in the mite population. The duration of the postcapping period was marginally related, and the other 2 characteristics were apparently unrelated to the growth of the mite population. This study showed that resistance to varroa mites is present in the honey bee population in the United States, nonreproduction of mites was highly correlated with the growth of a mite population, and nonreproduction of mites may be a valuable characteristic for selecting bees for resistance to varroa mites.

SUMMARYSuppressed mite reproduction (SMR) is a heritable trait of the honey bee (Apis mellifera) that can control the parasitic mite, Varroa destructor. The purpose of this study was to determine whether adult bees with the SMR trait affect mites in brood after cells are capped. Colonies with or without the SMR trait were each given a comb of newly-capped worker brood that was naturally infested with varroa. Each of 7 source colonies provided a comb of brood to at least one SMR (n = 9) and one control colony (n = 8). These combs were removed from their host colonies 8 days later and mite populations evaluated in cells with bee pupae that were >8 days post-capping. Colonies with SMR bees averaged 2.2% of their cells infested with mites; controls averaged 9.0%. Therefore, bees with the SMR trait apparently removed mites from capped cells. Of the mites that remained, the SMR colonies had a much lower rate of reproductive mites, 20% vs. 71%. This suggests that bees with the SMR trait removed reproductive mite...

SUMMARYSeveral experiments were conducted to examine the effects of exposure to CO2 or CO2 containing 20% O2 on the amounts of biogenic amines in the brain, and on development of ovaries in worker and queen honey bees. When workers were fed pollen and exposed to CO2, their ovaries were less developed and brain dopamine (DA), tryptophan (TRP) and tyrosine (TYR) levels were significantly reduced versus untreated controls that were also fed pollen. If workers were not fed pollen and exposed to CO2, the differences in brain amine content between untreated controls and CO2-treated workers were not significant; however, a significant reduction in brain TRP and TYR levels through time was found for both groups of workers. Treatment with CO2 stimulated free-running queens to lay eggs sooner than untreated free-running queens, but CO2 narcosis had no significant affect on queen brain chemistry. However, the brain chemistry of caged queens (many queens caged within a single colony) responded differently from free-r...

SUMMARYSignificant correlations between 25 quantitative characters of worker honey bees used for the morphometric identification of Africanized honey bees (Apis mellifera), seven measures of colony defence and 12 for alarm pheromone production were calculated from data on colonies in Louisiana, USA, and Monagas, Venezuela, two years after the arrival of Africanized honey bees in the eastern portion of Venezuela. The bees in the Venezuela group were identified as European (70%), European with evidence of introgression of Africanized genes (5%), Africanized with evidence of introgression of European genes (7%) and Africanized (18%), indicative of a population undergoing hybridization. For the Venezuelan population alone, the correlations between defensive behaviour and morphometric identification as Africanized were not significant. Therefore, defensive behaviour alone is not an adequate indicator for identification or certification programmes in areas undergoing Africanization.

This study measured the effects of hive volume on the productivity and growth of colonies of honey bees, Apis mellifera L., in Baton Rouge, LA. In a winter experiment, populations of 5,000, 10,000, and 15,000 bees were installed in hives to produce population densities of 150 or 550 bees per liter of hive volume (3 by 2 factorial, n = 60). More crowded bees consumed less honey (6.8 ± 1.9 mg per bee/d [mean SD] versus 12.2 ± 2.6 mg per bee/d) but produced less brood (0.34 ± 0.20 versus 0.72 -±0.31 cells per bee) and had a shorter life span than less crowded colonies. In spring, summer, and autumn, experiments were conducted with initial populations of 9,600 bees per colony. At 100, 200, 300, and 500 bees per liter ( n = 32), more crowded bees produced more honey. Average honey production was -70, -17, +28, and +67 g/d for the least to most crowded bees, respectively. More crowded bees produced less brood, but the difference was less marked than in winter. A final experiment measured the effects of adding hive space that did not contain comb ( n = 27). Of three treatments, colonies with five combs in a 25-liter hive produced the most honey (105 g/d), and colonies with additional space and combs (10 combs in a 47-liter hive) produced the least (29 g/d). Colonies with combless space (five combs in a 47-liter hive) were intermediate (62 g/d). The treatment with combless space produced more brood than the more crowded treatment but less than the treatment with 10 combs.

SUMMARYThe cost of rearing a worker honey bee (Apis mellifera) was measured in terms of honey lost by the colony and the lifespan of the adult worker bees. Test colonies for each experiment were created by collecting bees from many different sources into a large cage and then subdividing those bees to make a group of uniform colonies. Colonies were evaluated outdoors in Baton Rouge, Louisiana, USA, during February when there was pollen but no nectar for bees to collect. Brood production did not have a significant effect on adult survival during the first cycle of brood rearing, but colonies that reared more brood during the first brood cycle had greater adult mortality during the next brood cycle. Bees used 121 g of honey to produce 1 000 cells of mixed-aged brood (eggs, larvae and pupae in a normal brood nest) and about 163 mg of honey to rear one worker bee to the pupal stage. In colonies containing brood of all stages, the weight of brood was nearly equal to (about 25% less than) the weight of honey th...

SUMMARYTwelve white and 12 dark (unpainted) hives were set up in a sunny location in Baton Rouge, Louisiana, USA, on 7 May 1992. Each hive received a uniform colony of 5 048 ± 125 (mean ± s.d.) honey bees (Apis mellifera) that had been established from a single, artificially mixed population; 38% of the bees were infested with tracheal mites (Acarapis woodi). During June and July, bees produced more brood and honey in white hives than in dark hives. On 5 August, dark hives contained fewer tracheal mites than white hives; mites were found in 1 dark and 10 white hives (P < 0.001). In summer, the temperature in the space between brood combs in the dark hives often exceeded 40°C; maximum temperatures in the brood areas of dark and white hives, were 45°C and 38°C respectively. Laboratory tests showed that heat can kill tracheal mites inside live bees. A single six-hour exposure of bees to 42°C, a condition comparable to the short periods of high temperature encountered in field colonies, significantly reduced ...

A shorter development time for the honey bee ( Apis mellifera L.) would allow the parasitic mite Varroa jacobsoni Oudemans less time to reproduce and may provide the bee colony with some resistance to the mite. 1 developed an accurate way to measure development time, measured variance and heritability of development time of honey bees in Baton Rouge, and determined if colonies with rapidly developing workers produced more rapidly developing queens. Newly hatched larvae were obtained by placing combs that contained eggs into an incubator with no adult workers present. After waiting 1–3 h, newly hatched larvae were identifiable because they had no brood food in their cells. These unfed larvae from different colonies were transferred to a single comb and reared in a nurse colony. Workers ( n = 180) from 26 different colonies averaged (mean ± SD) 114.5 ± 4.3 h for the uncapped larval period and 285.4 ± 5.1 h for the capped period. Heritability ± SEM was 0.41 ± 0.15 for the uncapped and 0.61 ± 0.19 for the capped period. Stocks with rapidly developing workers did not always produce rapidly developing queens (queen-worker regression slope not > 0), so workers must be evaluated rather than queens. These data predict that selective breeding from 10% of the population should reduce the mean capped period of workers by 5 h in a single generation.

Because a solitary worker honey bee ( Apis mellifera L.) will not lay eggs, eggs were produced from small populations of caged workers. First, worker bees from four colonies were evaluated for their rate of worker ovary development. Groups of 25 workers were kept in incubator cages at 34 ± 1°C, and each cage was given an empty section of drone comb and unlimited supplies of honey, water, and pollen. Workers from colonies A and B began laying eggs rapidly (about 9 d), workers from colony D were intermediate (about 12 d), and workers from colony C required about 25 d. Five workers from colony A were mixed with 25 workers from the same colony, from colony B, or from colony C and maintained for 10 d. The five workers developed their ovaries most rapidly with their own sisters or with workers from colony C and slowest with unrelated, fast-developing workers from colony B ( P < 0.05). When a single worker from colony A was caged with 25 workers from colony C, all eggs were laid by the worker from colony A. Overall, 50% (19/38) of the workers from colony A became egg layers when they were caged alone with workers from colony C. Although workers from colony A developed their ovaries sooner than workers from colony C, the two groups had the same number of ovarioles. Yet, among sisters, ovaries with more ovarioles were significantly more developed than ovaries with fewer ovarioles.

SummaryIn each of 6 experiments, about 300 μl of honeybee (Apis mellifera L.) semen was diluted, mixed, and used to inseminate about 20 queens. The mixture for each experiment contained a portion of genetically marked sperm. Since the queens were also genetically marked, one could estimate the ratio of marked and unmarked sperm in each queen by counting her marked and unmarked progeny. The objective was to determine if each queen received equal proportions of marked sperm. In two experiments having semen mixtures with about 50% marked sperm, the 95% confidence interval for percent marked progeny was ±9·7% among the 22 queens in group 1 (semen was diluted 1:1 and stirred for 3·5 min) and ±9·0% among the 16 queens in group 6 (semen diluted 1:40 and centrifuged). The confidence intervals were similar and both were significantly greater than ±4·5% (expected 95% confidence interval when sampling a perfect mix with 500 workers from each queen) (P

SummaryNewly emerged worker honeybees (Apis mellifera L.) aged less than 24 h were placed into queen less cages and given a section of empty drone comb and unlimited supplies of honey, water and pollen. Cages were kept in an incubator at 34 ± 1°C. Workers treated with a 15-min exposure to CO2, at 0–3 days of age produced significantly fewer eggs than controls that received no CO2;. Workers in queenless cages for 4–6 days before CO2 narcosis had egg production equal LO that of controls. Thus CO2, had no apparent effect after the workers had been queenless for 4 days. In a second study, 5 untreated workers shared cages with 25 sisters that had been treated with three 15-min doses of CO2. Association with the treated workers retarded ovary development of the untreated cagemates when compared to sister bees in identical cages that contained no bees given CO2, Cages with treated workers consumed only 17% as much pollen as controls. So low pollen consumption may have reduced the total amount of protein that was...

This study examines changes in reproduction and mortality of Varroa destructorwhen queens from stocks of honey bees (Apis mellifera L.) that differ in susceptibility to the mites were exchanged between colonies. Queens were selected for suppression of mite reproduction (SMRD). In two experiments uniform colonies of bees were established; half the colonies were given queens selected for SMRD, and half were given unselected queens. Queens were exchanged after 7 (exper- iment 1) and 13 weeks (experiment 2). The percentage of mites that had no progeny was determined for each colony at 5 times (2 before and 3 after exchanging queens). Mites that had no progeny included live and dead mites. Results showed (1) that reproduction of mites is suppressed by adding a queen selected for SMRD, and (2) that a mite population recovers its reproduction when a SMRD queen is replaced by an unselected queen. Selection of the SMRD trait can be reduced to counting only live mites that laid no eggs and dead mites. Apis mellifera / Varroa destructor / resistance to pests / suppression of mite reproduction (SMRD)

About 7 kg of honey bees were caged, stored for 2 days, and subdivided into 3 populations: ca. 4,400, 8,900, and 34,000 bees. The bees then were placed in hives that had no brood and a known quantity of honey. The resulting colonies had ca. 2 liters of space and one caged queen per 1,000 bees. Worker survival, honey loss per bee, colony temperature, and survival of caged queens were compared in six replicates. Each replicate covered 20 to 27 days during winter in Baton Rouge, La. Population size had no effect on survival of workers or caged queens. However, larger populations were significantly warmer than smaller populations when the ambient temperature was

Population growth was compared in 21 colonies of honey bees, Apis mellifera L., during the period of maximal population growth in Louisiana. Each colony began with 1.25 kg of bees, no brood, and 40 liters of hive space (measured empty). Colonies differed in comb size (13 by 19, 13 by 43, 20 by 43, or 26 by 43 cm), but each hive had the same comb surface area (1.1 m2). Bees were put into hives on 12 March, queens were released 15 March, and hives were expanded to 1.4 m2 of comb surface area and 48 liters on 10 April. Colonies with the largest combs produced more brood and had more adult workers on 13 May than colonies with the two smallest combs. At the end of the experiment, mean adult populations were 19,300, 22,900, 23,600, and 28,400 in colonies with the smallest to largest combs, respectively. A second experiment compared comb effects versus queen effects by measuring the amount of brood produced in 10 d by colonies with instrumentally inseminated or naturally mated queens on either the largest or smallest comb sizes. Comb effects were significant, queen effects were not. Small combs reduced brood production and diminished differences among queens; therefore, one must use large combs when evaluating queen fecundity.

Honey bee, Apis mellifera L., queens were inseminated with semen that had been stored in liquid nitrogen (−196°C). Daughters (F1 queens) were produced, and eggs from these F1 queens were measured for viability. All eggs were kept in an incubator (35°C, 50 to 70% RH) for their entire developmental period. The percent mortality of fertilized eggs (F2) in one test group differed significantly ( P < 0.05) from controls (mean [$\bar x$] ± SD was 5.6 ± 5.0% for eggs in the test group and 2.6 ± 1.5% for controls). No significant differences were found between test and control eggs in another unrelated group of fertilized eggs or between test and control eggs that were not fertilized. In a survey of fertilized eggs in 46 normal colonies of bees near Baton Rouge, La., the mean mortality was 7% and the median was 5%. Unfertilized (haploid) eggs had a consistently higher mortality rate than fertilized (diploid) eggs. A typical group of queens, 12 producing fertilized eggs and 12 others producing unfertilized eggs, averaged 5.0 ± 5.0% ($\bar x$ ± SD) mortality for fertilized eggs and 18.4 ± 9.8% for unfertilized eggs.

A new method of handling and storing the semen of lioney bees, Apis mellifera L., permits collection, storage, and insemination without the need to transfer semen from the insemination syringe to the storage tube and back again. A modified capillary tube serves as both an insemination tip and a storage container. When the semen has been collected into this tube, the tube is detached from the specially designed syringe, both ends are sealed with petrolatum, and the tube is ready for storage. When semen is needed, the tube is replaced onto the syringe, the smaller petrolatum plug is forced out of the pointed end, and insemination proceeds.

SummaryThe effect of population size on brood production, worker survival and gain or loss of honey was studied in colonies of honeybees (Apis mellifera) in Louisiana, USA. About 11 kg of bees were caged, stored for two days and subdivided into five populations numbering 2300, 4500, 9000, 17 000 and 35 000 bees. Each colony was started with a laying queen, no brood, and 230 bees per 1000 cm3 of hive space. The test ended 19 days after queen release, just before adult bees began to emerge. The test was conducted 10 times (two replicates being used in each of February, April, June, August and October). The two largest populations produced more honey per bee and in dearth times and winter consumed less honey per bee. Colonies of 4500 bees produced the most brood per bee; as population increased above that number brood production per bee decreased. However, during summer dearth, the colonies of 9000 bees produced the most brood per bee. Overall, the optimal colony size was 9000 bees; the rate of weight gain i...

SummarySister queen honeybees (Apis mellifera), 59 instrumentally inseminated (IIS) and 59 naturally mated (NM), were produced in Baton Rouge, Louisiana, and put into field colonies at 3 locations in Alberta, Canada and at 1 location in Louisiana, USA. Survival of the IIS queens was lower than that of the NM queens; 37 IIS queens and 50 NM queens survived from August 1981 to May 1982, and 18 IIS and 34 NM queens survived until August 1982 (P

SummaryAfricanized and European honeybees (Apis mellifera) responded differently to daily fluctuations in nectar resources. In side-by-side comparisons, the relative energy content of the nectar loads collected by the two geographical types varied with day. Daily variation was found in the volume of nectar collected but not in its concentration. Africanized bees collected more highly concentrated nectar. The success rates of foragers of the two types differed considerably. European bees generally were more successful in securing a load of nectar but their percentage of successful foragers tended to be either high or low. Africanized bees returned more often to their nest without a nectar load but had intermediate as well as high and low percentages of successful foragers. Finally, European colonies had greater numbers of foragers under the nectar-resource conditions of the study.

SummaryMultiple inseminations of the queen honeybee with small volumes of diluted semen resulted in significantly more spermatozoa entering the spermatheca than did single inseminations of the same total volumes (P < 0·01). In three experiments with small, equal insemination volumes, the second insemination contributed more spermatozoa to the spermatheca than did the first. For inseminations of semen that had been stored in liquid nitrogen (—196°C), the second insemination contributed 77% and 68% in two different experiments. With fresh diluted semen the second insemination contributed 61%.

Drone production between 2 groups of worker honeybees (Apis mellifera L.) was compared in Baton Rouge, Louisiana : an older heterogeneous population of bees (> 54 days old at beginning of egg laying period), and a smaller group of young bees (11-15 days old). Six of 9 broodless, queenless colonies (providing the «old » bees) were each given 150 young bees that were heterozygous for visible mutations. The remaining 3 colonies were controls. Young workers produced a much higher proportion of drones in 3 of 6 the test colonies than did the old workers (Tabl. 1). Old workers produced at least as many drones per bee as did the young workers in the other 3 test colonies. Workers 2* 54 days old produced eggs in all colonies.

SummaryA method for storing honeybee spermatozoa in liquid nitrogen is described. A hydraulic syringe attached to a meter accurately measures collection, dilution, and delivery of semen, and a thermocouple inserted into the semen records the rates of freezing and thawing. From collection to insemination the storage process lost only 7% of the semen mixture.A mixture of 60% semen, 10% dimethyl sulphoxide (DMSO) and 30% saline was the most successful for storage. Glycerol gave some protection as a cryoprotectant, but was inferior to DMSO. After semen was stored with 10% DMSO and 30% water, more spermatozoa moved to the spermatheca than after storage with 10% DMSO and 10% or 20% water.

SummaryMost feral swarms of Africanized honeybees (Apis mellifera, South American ecotype) in Venezuela selected cavities with a volume of 80 litres as nest sites when presented with a choice of 10, 20, 40 and 80 litres. Agonistic behaviour between scout bees inspecting nest boxes was common, indicating that nest cavities were a limited resource for this population of feral honeybees.

SummaryThe effects of queenlessness on worker honeybees (Apis mellifera?) were tested with 50 colonies in groups of 10 (five treatments and two replicates) in August, October and December, 1984 and February and April, 1985 in Baton Rouge, Louisiana. The 10 colonies in each group were all from a single heterogeneous mixture of bees, and each colony began with about 6000 workers and no brood. The five treatments each lasted for 28 days and consisted of (1) caged queen for 28 days, queenless for 0 days; (2) caged queen for 21 days, queenless for 7 days; (3) caged queen for 14 days, queenless for 14 days; (4) caged queen for 7 days, queenless for 21 days and (5) caged queen for 9 days, laying queen for 19 days (control). With prolonged queenlessness worker survival, colony weight gain and defence behaviour (number of stings) decreased. Queenlessness did not induce drifting.

SummaryFourteen uniformly inseminated hybrid queens were randomly divided into three groups. Spermatozoa in the Spermatozoa of the first group were counted before egg laying began (5.00 ± 0.26 (SE) million). Queens of the second group laid about 63 000, and of the third group about 123 000, eggs before spermatozoa in the spermathecae were counted (3.25 ± 0.06, 2.49 ± 0.18, respectively). The queens used half their spermatozoa between 16 June and mid-November—about half the egg-laying season in Louisiana. The data were negatively correlated with the predicted logarithmic loss of spermatozoa from the spermatheca (r = −0.94).

Egg-laying rates of queen honey bees, Apis mellifera L., were measured in colonies containing no brood and ca. 3,000 or 12,000 worker bees. Naturally mated queens were heavier and laid more eggs per day than instrumentally inseminated queens. CO2 narcosis caused weight loss in queens and may account for at least some of the difference. When nitrogen narcosis replaced carbon dioxide during instrumental insemination, queen weights increased, but still did not equal those of naturally mated queens that received no narcosis. The correlation between egg-laying rate and queen weight was r = 0.73 ( n = 112).

SummaryIn a side-by-side test in Venezuela, 593 eggs from 7 Africanized queen honeybees and 355 eggs from 7 European queens (from USA) were kept in an incubator (35 ± 1°C) without adult bees. Eggs from the two groups hatched after 69·6 ± 1·06 h and 73·3 ± 1·14 h, respectively (x ± SD), indicating a basic physiological difference between development periods for eggs from the two populations.

A bioassay was developed to evaluate diluents of honey bee ( Apis mellifera L.) semen. Using a simple diluent (1.1% NaCl, 0.1% glucose, 0.01% each L-arginine HCl, L-glutamic acid, L-lysine, 0.02% dihydrostreptomycin sulfate, and 0.012% penicillin G sodium in 0.05 M Tris buffer at pH 8.7), 100-fold dilution, incubation at 35 ± 1°C for 10 min. and reconcentration did not reduce the number of spermatozoa that reached the spermathecae of instrumentally inseminated queens. Undiluted control semen had a 10.9% transfer efficiency when 15 × 106 spermatozoa were injected into the oviducts of each queen. Treated groups of semen incubated for 0.17, 1.5, 3.0, 4.5, 6.0, 7.5, and 19.5 h had transfer efficiencies of 10.7, 8.8, 9.8, 5.1, 2.1, 4.3, and 2.4%, respectively.

Africanized and European honey bee (Apis mellifera) populations showed quantitative differences in colony defensive behavior. Africanized bees responded faster and in much larger numbers than European honey bees and produced 8.2 and 5.9 times as many stings during two different experiments. Times to react to alarming stimuli were negatively correlated with the number of bees responding and to the total number of stings. The number of bees responding was significantly correlated to the total number of stings only for the Africanized population.

The development times of female eggs of the honey bee, Apis mellifera L., were significantly shorter (P < 0.01) than development times of male eggs. Throughout their developmental period, the eggs were kept in an incubator (34.8°C, 60 to 80% RH) without adult bees. Haploid and diploid male eggs required about 3 h longer than female (always diploid) eggs. It is not known whether the development times of haploid and diploid male eggs are significantly different. Female eggs from 20 unrelated queens had mean development times that ranged from 68.8 to 74.2 h at 34.8°C; the 20 means averaged 71.4 ± 1.2 h (SD). The development times were altered by very slight changes in temperature. Female eggs kept at 34.8°C hatched about 1.4 h sooner than those kept at 34.3°C. Only 1% of the eggs hatched when kept at 29.8°C.

technique was derived for measuring the concentration of sperm in honey bees, Apis melifera L., by spectrophotometric absorbance. A positive linear correlation (r = 0.957) existed between absorbance at 230 nm and sperm concentration in 0.5 M NaCl. With our spectrophotometer, the formula correlating milions of sperm per 5 ml (x) to absorbance (y) was y = -0.0096 + 0.1224x.

When laying in worker comb, queen honey bees, Apis mellifera L., that were inseminated with live semen laid eggs in 3.0-9.6 times more cells than did queens that were not inseminated or were inseminated with frozen (nonfunctional) semen. Also when queens inseminated with live semen laid in a small colony, 0-7% of the cells with eggs had an egg positioned sideways or on the side of the cell. In contrast, this percentage rose to 33-94% when queens were not inseminated or were inseminated with frozen semen. These differences in behavior may arise from a disruption of the egg fertilizing phase of egg laying.

SummaryHoneybee (Apis mellifera) semen was diluted 1: 1 with saline and stored at 5, 10, 15, 20, 25 or 35°C for 2 days, or was not stored (control). Each of 111 queens was inseminated with 4 μ1 of the diluted semen. The effects of storage temperatures were evaluated by counting the number of spermatozoa that entered the spermatheca. Mean counts were ⩽3·1 × 105 when spermatozoa were stored ⩽10°C; storage at 20°C and 25°C resulted in the highest counts (mean = 1·4 × 106). The response in millions of spermatozoa in the spermatheca (Y) to storage temperature between 10 and 25°C (X) was Y = −2·74 + 0·397X–0·00935X2 (r = 0·78, n = 34).

Honey bee (Apis mellifera L.) semen was diluted with water (or 0.85% NaCl) and dimethyl sulfoxide in a 6:3:1 ratio and stored in liquid nitrogen (–196° C). Queens inseminated with this semen produced a higher proportion of males (unfertilized eggs) and a lower egg hatching rate than control queens. Low hatching rates were associated with the fertilized eggs rather than with the unfertilized eggs within the test group. Egg hatching rates averaged 82±11% (x±SD) in test queens and 95±2% in controls.

Mosaic male honey bees were found as the progeny of queens that had been inseminated with spermatozoa stored in liquid nitrogen. The origins of these mosaics and the genotype of their gametes were determined by using mutant markers. The mosaics probably developed from an egg pronucleus and a sperm pronucleus that did not unite after the latter had entered the egg. Instead, both pronuclei produced haploid tissue independently. The three mosaics that were mated to queens all had mosaic testes. Therefore, these were situations in which a male honey bee produced two types of spermatozoa.

Honey bee (Apis mellifera) semen was treated as follows: diluted in saline with 10 percent dimethyl sulfoxide (DMSO) and stored at -196 degrees C; same treatment but stored at 12 degrees C; diluted in saline and stored at 12 degrees C; and undiluted, unstored semen. Daughters (queens) produced from the treated spermatozoa were evaluated for total sterility. Only sterile eggs were produced from 3 percent of the queens in both groups that had DMSO (5/166 in group 1, and 6/234 in group 2). They were different (P less than 0.05) from groups 3 and 4 in which no queens were produced that laid only sterile eggs (0/151 and 0/137, respectively). These results demonstrate that, under the conditions used, a low level of sterility is induced by DMSO, and this F1 sterility raises questions about possible genetic damage by DMSO.

Of 12 alarm pheromones assayed in European and Africanized honeybees, nine were found in larger quantities in the Africanized population. Isopentyl and 2-heptanone levels were similar in both; 2-methylbutanol-1 was greater in European workers. These differences were not due to age or geographical location. Significant positive correlations between alarm pheromone levels and defensive behavior, especially numbers of stings, were observed.