Bangkok 10600, Thailand. Dhonburi, Bangkok 10600, Thailand. *Corresponding author Accepted 12 February, 2016 ABSTRACT

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1 Basic Research Journal of Agricultural Science and Review ISSN -880 Vol. () pp. 7- February 0 Available online http// Copyright 0 Basic Research Journal Full Length Research Paper Reproduction of the bee mite, Varroa destructor Anderson and Trueman (Acari: Varroidae), in worker brood cells of Primorsky and Thai commercial honey bees (Apis mellifera Linnaeus) Boonmee Kavinseksan *, Siriwat Wongsiri, Amonnut Chotkitnusorn Department of Science, Faculty of Science and Technology, Bansomdejchaopraya Rajabhat University, Dhonburi, Bangkok 000, Thailand. Graduate School, Maejo University, San Sai, Chiang Mai 090, Thailand. Department of Applied Science, Faculty of Science and Technology, Bansomdejchaopraya Rajabhat University, Dhonburi, Bangkok 000, Thailand. *Corresponding author boonmee7@yahoo.com Accepted February, 0 ABSTRACT Fifteen Primorsky honey bee (Apis mellifera) and Thai commercial colonies, Italian honey bee hybrids, were investigated of Varroa destructor non-reproduction and the number of progeny produced by reproductive mites (or fecundity). Primorsky and Thai commercial colonies were established and placed in an apiary in Chiang Mai, Thailand. Capped brood cells of the Primorsky and Thai commercial colonies were examined and determined for non-reproductive mites and fecundity after one year of queen introduction (in September 0). Dark brown eyes with light pigmented thorax pupae and older of the Primorsky and Thai commercial colonies were examined, and only cells that had been invaded by a single female mite were evaluated for non-reproductive mites and fecundity. Criteria for nonreproduction were mites that did not lay eggs and mites with progeny that were too young to mature before the host bee emerged from its cell. The percent mean of non-reproductive mites on the worker pupae of Primorsky (.+0.%) was significantly higher (P=0.00) than that of Thai commercial (.+0.8%) colonies (percent mean + standard error). V. destructor fecundity of reproductive mites in Thai commercial ( progeny per female mite) was significantly higher (P=0.00) than that of Primorsky (.+0.0 progeny per female mite) colonies (mean + standard error). Keywords: Non-reproduction, Apis mellifera, Thai commercial honey bee, fecundity, Primorsky honey bee, Varroa destructor INTRODUCTION The ectoparasitic honey bee mite Varroa destructor Anderson and Trueman (Acari: Varroidae) is one of the most dangerous parasites of the Western honey bee (Apis mellifera Linnaeus) causing enormous A. mellifera colony losses worldwide (Anderson and Trueman, 000; De la Rua et al., 009; Lattorff et al., 0). The Varroa mite was originally confined to the Eastern honey bee (A. cerana). After a shift to the new host A. mellifera during the first half of the last century, the parasite dispersed worldwide. Management of Varroa mites generally

2 Kavinseksan et al. 8 requires the use of acaricides. However, injudicious use of acaricides may pose residue problems, especially in wax and honey (Lodesani et al., 99; Bogdanov et al., 998; Kochansky et al., 00; Martel and Zeggane, 00). It may also lead to the development of mites resistant to acaricides (De Guzman et al., 008). The use of resistant A. mellifera stocks to V. destructor has been thought to be a better solution to the Varroa problem. The benefits of using resistant honey bees to parasitic mites include: less chance of contaminating bee products with undesirable chemicals, low cost of labor and materials and less risk of the mite developing resistance to acaricides (Kavinseksan, 00). Primorsky honey bees (A. mellifera) are known to be resistant to V. destructor and Acarapis woodi (De Guzman et al., 99; Rinderer et al., 997, 999, 00). In Thailand, the Primorsky bee has showed more efficient grooming behavior to remove and kill Varroa mites (.9%) and T. mercedesae (77.%) than the Thai commercially domestic bee (A. mellifera) (7.8% for V. destructor and 7.% for T. mercedesae) (Kavinseksan, 0, 0). Also, both Primorsky and Thai commercial bees had the similar rate of brood removal (8.-8.%) or hygienic behavior (Kavinseksan et al., 00). However, other defense mechanisms of Primorsky and Thai commercial honey bees to resistance against V. destructor in Thailand have not yet to be studied. Mite non-reproduction is one of many defensive mechanisms of honey bees that has been associated with resistance to mites (Buchler and Drescher, 990; Spivak and Reuter, 998; Kavinseksan, 00; Khongphinitbunjong et al., 0). This is especially true in studies of A. mellifera infested by V. destructor (Rinderer et al., 00). The control of mite reproduction is considered the most effective tool for the host to prevent the growth of a Varroa population within the colony (Fries et al., 99; Calis et al., 999; Milani et al., 00). Nonreproduction of 0% or more negatively affects Varroa mite population growth (Harbo and Hoopingarner, 997). V. destructor can reproduce in both drone and worker brood of A. mellifera. However, Varroa females which have entered a drone or worker brood cell do not lay any egg at all. The percentage of non-reproducing mites is slightly variable according to the species or subspecies of the bee host and might, therefore, contribute to differences in the host tolerance of European bees (Fries et al., 99; Martin, 998; Rosenkranz, 999). In European honey bee subspecies, about -0% of the mites remain infertile after invading worker or drone brood cells (Martin, 99, 99a; Rosenkranz and Engels, 99; Martin et al., 997; Rosenkranz, 999; Garrido et al., 00; Al Aattal et al., 00). The higher infertility rate about 0% in worker brood was found in the Africanized honey bees of Brazil (Rosenkranz, 999). However, non-reproductive rates of V. destructor females in brood cells of Primorsky and Thai commercial honey bees has never been compared. Therefore, this research was conducted to evaluate for rates of non-reproducing and reproducing V. destructor foundress mites in Primorsky colonies and commercially available A. mellifera colonies in Thailand, which is an important character in the regulation of mite populations in the colonies. In addition, rates of fecundity for reproducing mites in Primorsky and Thai commercial colonies were determined. MATERIALS AND METHODS Establishment of the test colonies Fifteen Primorsky (A. mellifera) and Thai commercial colonies (A. mellifera, Italian honey bee hybrids) were used to estimate for V. destructor non-reproduction and fecundity of reproductive mites. The Primorsky queen bees were received from the USDA, Honey Bee Breeding, Genetics and Physiology Laboratory in Baton Rouge, Louisiana, USA, while the Thai commercial queen bees were received from Supa s apiary in Chiang Mai, Thailand. These honey bees were established in Langstroth hives and placed in an apiary in Chiang Mai, Thailand, in September 0. Experimental procedures were carried out about one year (in September 0) after queen introduction. For each colony, about,00 sealed worker brood cells were cut from three different combs (about 00 cells on one side) and immediately frozen. Worker brood cells in each colony were examined and determined for non-reproductive and reproductive mites. The frozen capped brood of Primorsky and Thai commercial bees was later thawed, and cells that contained a pupa which was at least sufficiently mature to have dark brown eyes and a lightly pigmented thorax (Pdl stage, 7-8 days old including the egg stage) (Rembold et al., 980) or older were opened and inspected with the aid of a sterio-microscope at 0X magnification. For each inspection, the pupa was removed from the cell and examined for mites. Then, the cell itself was examined. Cells which contained only one foundress as indicated by the dark color of her integument were scored for reproduction and non-reproduction. Determinations of mite progeny age and sex were based on a morphological characterization of V. destructor nymphal and adult stages, and the expected age of mite progeny at the time the bee in the cell would have emerged was estimated according to the developmental periods according to the descriptions of Martin (997). Only worker brood was evaluated since the colonies we have studied had not very drone brood. The numbers of cells infested with more than one foundress were counted. The percent means of cell numbers infested by only one and more than one foundresses in Primorsky and Thai

3 9. Basic Res. J. Agric. Sci Rev. commercial colonies were analyzed using t-tests (SPSS statistic program). Percentage of non-reproductive mites A reproductive foundress mite was one that would have produced at least mature female daughter before the host bee emerged from its cell. Bee pupae in Pdl stage or older was examined to determine the reproductive success by mites in cells that had been infested with a single female mite. At this stage of host development, it is too late for mite eggs to mature to adult mites. Mites were considered non-reproduction when they had no progeny beyond duetonymph by the time bee pupae had matured to the Pdl stage. Harbo and Harris (999) divided nonreproduction into categories: () mites that died in the cell before laying eggs, () mites that were alive in the cell but did not lay eggs, and () mites with female progeny that were too young to mature before the host bee emerged from its cell. In this study, we could not distinguish between categories one and two since the combs were frozen prior to examination. We assumed that most of the mites were dead because they were frozen. The percentage of non-reproductive mites in each colony of the Primorsky and Thai commercial bees was calculated. The percent means of non-reproductive mites in cells infested by only one foundress in the Primorsky and Thai commercial colonies were analyzed using t- tests (SPSS statistic program). The honey bee colonies were used as replications. Fecundity of reproductive mites The number of progeny produced by reproductive mites (or fecundity) from cells infested by one female mite was recorded. Only mites from worker pupae in Pdl stage or mites on pupae in older developmental stages were counted. This analysis did not include non-reproductive mites, which includes mites that produced progeny too late to mature. The average number of progeny produced by a reproductive mite in brood cells infested by single and multiple foudresses in each colony was calculated. The data on fecundity of reproductive mites in cells infested by single and multiple foudresses of the Primorsky and Thai commercial colonies was analyzed by t-tests (SPSS statistic program). The colonies of honey bees were used as replications. Pearson correlation analysis was used to test the relationships between the number of progeny produced by reproductive mites and the number of non-reproductive mites. RESULTS AND DISCUSSION V. destructor infestations If an A. cerana drone cell is invaded by more than one Varroa mite, there is a greathly increased chance that those mites will kill their host (Rath, 99). In A. mellifera, many mother mites can invade a single cell and reproduce successfully without killing the host bee (Boecking and Ritter, 99). In this study, the percentage of cells per colony which were infested with only one V. destructor foundress and contained worker Pdl or older pupae of Thai commercial colonies was significantly higher than that of Primorsky colonies (t=.7, df=8, P=0.00) with the mean of and. + 0.% (percent mean + standard error), respectively (Table below). Also, the percentage of cells infested by more than one V. destructor foundresses on the worker pupae of Thai commercial colonies was significantly higher than that of Primorsky colonies (t=.80, df=8, P=0.00) with the mean of and % (percent mean + standard error), respectively (Table below). Generally, mite attractiveness of bee brood is measured as the percentage of cells infested (Rinderer et al., 00). The results here suggest that the Thai commercial brood had more attractive Varroa mites than the Primorsky brood. A low attractivity of the Primorsky brood may reduce the invasion rate of Varroa females. The nature of different brood attractivity is unknown, but the effect of bee races are related to differential Varroa infestation rates (Aumeier et al., 00). Larval food may also contain chemicals that attract Varroa mites (Nazzi et al., 00). When the Western honey bee, A. mellifera, was introduced into the area of A. cerana, V. destructor successfully switched hosts from A. cerana to be A. mellifera and has become a severe pest of A. mellifera (Fuchs and Langenbach, 989; Anderson, 99; Martin, 99b; Anderson and Sukarsih, 99; De Jong, 997; De Guzman et al., 998; Oldroyd, 999; Garrido et al., 00; Martin and Medina, 00; Mondragon et al., 00; Oldroyd and Wongsiri, 00; Munoz et al., 008; De la Rua et al., 009; Le Conte et al., 00; Rosenkranz et al., 00) because A. mellifera lack of essential defensive mechanisms to limiting the population growth of V. destructor in its colony (Wongsiri et al., 989). Mite reproductive rates would be reduced if adult workers detect infested brood cells and remove the pupae before the mites can reproduce (Spivak 99) or remove mites from the bodies of nestmates (grooming behavior) (Fries et al., 99). Primorsky and Thai commercial bees had the similar rate of brood removal (8.-8.%) (Kavinseksan et al., 00), but the Primorsky bee has showed more efficient grooming behavior to remove and

4 Kavinseksan et al. 0 Table. Numbers of worker brood cells in dark brown eyes with light pigmented thorax pupae and older infested by single foundresses of V. destructor and their rates of reproduction and non-reproduction in colonies of Primorsky and Thai commercial honey bees Colony Primorsky Total or average Thai commercial Total or average No. of cells inspected,0,7,,890,9,,90,9,90,7,0,0,8,78,09 No. of cells infested by only foundress Percentage of cells infested by only foundress (Mean±S.E) Non-reproductive mites Reproductive mites N Percentage No Delayed N Percentage non-reproductive eggs eggs (%) reproductive (Mean±S.E) (%) (Mean±S.E) ,88,0. ± 0. b. ± 0. a 09 (9.8),0,77,8,,07,8,97,87,,0,00,8,0,7, ,7,. ± 0.7 a. ± 0.8 b 98 (9.9) Similar letters in the same column are not significantly different at the 0.0 level (.) 0 7 (.) No. of progeny Progeny per mite (Mean±S.E) ± 0. b 70. ± 0.0 b ,7 8. ± 0.8 a,98. ± 0.07 a

5 . Basic Res. J. Agric. Sci Rev. Table. Numbers of V. destructor daughters in Primorsky and Thai commercial worker brood cells in developmental stages of dark brown eyes with light pigmented thorax pupae and older having more than one foundress and the average reproductive rate in multiply infested cells Colony No. of cells examined Number of cells infested by more than foundress Percentage of cells infested by more than foundress (Mean±S.E) Number of foundresses Number of daughters Primorsky ,0,7,,890,9,,90,9,90,7,0,0,8,78, Total or average 0,88.7 ± 0. b 7 8 ± 0.0 b Thai commercial, ,77.9.0, ,.8.0, , , , ,.. 0,0.., ,8. 7., ,7..0, Total or average 7,7 9. ± 0. a ± 0.0 a Similar letters in the same column are not significantly different at the 0.0 level. Number of daughters per foundress in multiply infested cell (Mean±S.E)

6 Kavinseksan et al. kill Varroa mites (.9%) than the Thai commercially bee (7.8%) (Kavinseksan, 0). Thus grooming behavior of the Primorsky bees was more prevention the mites from entering cells and reproducing than the Thai commercial bees. Non-reproduction of V. destructor Mite non-reproduction is a genetic trait of bees (Harris and Harbo, 00) and one of many resistant mechanisms of honey bees to mites (Buchler and Drescher, 990; Boecking and Drescher, 99). Mite growth was low in colonies with the high percentage of non-reproductive mites (Harris and Harbo, 00). In worker brood cells infested with one V. destructor female in this study, the percentage of non-reproductive mites on Pdl pupae and older of Primorsky colonies was significantly higher than that of Thai commercial colonies (t=.8, df=8, P=0.00) with the mean of and % (percent mean + standard error), respectively (Table ). This result showed that the Primorsky bees had more suppression to V. destructor reproduction than the Thai commercial bees. De Guzman et al. (008) reported that the comb built by Primorsky bees contributed to an increased non-reproductive rate of Varroa mites. Also, the high rate of non-reproduction in the Primorsky honey bees (.%) by infesting mites may result from reduced brood attractiveness. The percentage of non-reproductive mites in the Primorsky colonies (.%) in this study was the similar rate in Africanized bee colonies in Brazil (%) and higher than the non-reproductive rate in European race A. mellifera (9%) in the previous reports by Camazine (98) Moretto et al. (99) and Rosenkranz (999). Non-reproduction of Varroa mites is a mite-bee interaction in colonies in which Varroa mites show impaired reproductive ability (Anderson, 99). The cause of this non-reproduction is exactly unknown. However, evidence suggests that certain factors can be possible causes. Harbo and Harris (999) reported that a genetic characteristic of bees caused mites to become non-reproductive and is a heritable characteristic of honey bees. Chemicals from larva and prepupa s haemolymph stimulate Varroa mites to produce and lay eggs (Harris and Harbo, 00). Several researchers have reported on the role of juvenile hormone as a trigger for Varroa mite reproduction. Exogenous application of juvenile hormone to bee larvae increased reproduction of Varroa mites (Hanel, 98, 98; Hanel and Koeniger, 98; Rosenkranz et al., 989, 99). However, endogenous juvenile hormone titers are similar in bee larvae from races and species of bees that differ dramatically in their abilities to support mite reproduction (Rosenkranz et al., 989, 99). It is possible that some substances in bee s haemolymph may affect nonreproduction of Varroa mites (Rosenkranz and Engels, 99; Martin et al., 997; Garrido et al., 000). A glucose methanol choline oxidoreductase might be involved in changing volatiles emitted by bee larvae that might be essential to trigger oogenesis in Varroa mites (Lattorff et al., 0). Chemical signals of the th instar spinning larvae initiate oogenesis in Varroa mites when entering the cell shortly before capping (Garrido and Rosenkranz, 00). Fatty acid ethyl esters on surfaces of worker larvae within the first h after the cell capping possess the entire capacity to activate the reproduction of V. destructor females. The rate of reproducing Varroa females decreased significantly if they were introduced into brood cells 8 h (worker) after cell capping (Frey et al., 0). Various environmental factors affect the percentage of non-reproductive Varroa mites in colonies of bees. High temperatures and relative humidity increased the percentage of non-reproductive Varroa mites (Le Cont et al., 990; Kraus and Velthuis, 997). A higher percentage of non-reproductive Varroa mites occurred in colonies from tropical climates than in those from moderate climates (Harris and Harbo, 00). High non-reproductive rates of V. destructor in Primorsky colonies (.%) and Thai commercial colonies (.%) in this study might be affect on high temperatures and relative humidity in Thailand, which locates in tropical climate. From the data obtained, the percentage of nonreproductive mites that did not lay eggs in the Primorsky and Thai commercial colonies was 9.8 and 9.9%, respectively (Table ). This suggests that nonreproduction could be related to non-mating of the Varroa mites. Unfortunately, the reasons for the infertility of Varroa females are unknown. As unfertilized females are not able to reproduce (Fuchs, 99; Martin et al., 997) it was assumed that these infertile mites represent young Varroa females which failed to copulate during their maturation. Harris and Harbo (00); Kirrane et al. (0) reported that many non-laying egg Varroa mites had no stored sperm, and Varroa females used the stored sperm to produce eggs after entering brood cells for reproductive cycles. In cells infested by Varroa foundress, mating in V. destructor is between brother (male) and sister (females) and occurs within the sealed cell. If females are not mated soon after moulting, e.g. due to the premature death of the male, they are unable to produce any viable offspring and are therefore nonreproductive, or infertile (Boot et al., 997). The production of one adult viable daughter requires at least the maturation of one male and one female offspring including mating. Therefore, female mites producing only one egg, no males or with delayed start of oviposition may not contribute to the growth of the Varroa population. Eguaras et al. (99) reported that a high infertility was associated with a greater lack of males. When mites produce daughters but no living male, the daughter mites will remain unmated in single infested cells (Boot et al. 997). These unfertilized mites cannot mate once they

7 . Basic Res. J. Agric. Sci Rev. have emerged from the cell and so never produce viable offspring, although they do enter cells and attempt to reproduce. A high rate of -% mortality suffered by the first (specifically the male) and second (female) mite offspring found in worker brood cells of Africanized honey bees is thought to contribute in part to the tolerance of these bees (Donze et al., 99; Martin et al., 997; Medina and Martin, 999; Calderon et al., 0). The mortality of mite offspring seems to be a main factor for differences in the reproductive rate and varies according to climate, season and honey bee subspecies (Eguaras et al., 99; Ifantidis et al., 999; Mondragon et al., 00, 00). In this study, the percentage of non-reproductive mites with progeny that were too young to mature before the host bee emerged from its cell (delayed eggs) in the Primorsky and Thai commercial colonies was. and.%, respectively (Table ). This finding was consistent with the previous report by Martin (00) that V. destructor has a high degree of adaptation with its host. This bee mite has greatly compressed its early developmental stages by omitting the normal -legged larval stage (Steiner et al., 99). Also, proteins ingested by the mite from the bee s blood can be detected unaltered in the mite s egg, which again may help speed up development (Tewarson and Engels, 98). Varroa mites that were sandwiched between the cocoon that is spun by the host larva and the cell wall (entrapped by the cocoon) were not found in this study. Few entrapped Varroa mites (-%) were found in unselected A. mellifera colonies, but more than 0% of mites in colonies of bees bred for suppression of mite reproduction were entrapped (Harris and Harbo, 00). In this study, Varroa mites died during reproduction were not found since we assumed that most of the mites were dead because of being frozen. Martin (99, 99a) reported that a small number (-%) of the mother mites died during reproduction. Mite fecundity Measurements of the reproductive potential of infesting Varroa mites are more useful than attractive measurements (Rinderer et al., 00). The actual reproductive rate for V. destructor was calculated from reproductive mites. In worker brood cells infested by single foundresses of V. destructor in this study, the percentage of reproductive Varroa mites on Pdl pupae and older of Thai commercial colonies was significantly higher than that of Primorsky colonies (t=.89, df=8, P=0.00) with the mean of and % (percent mean + standard error), respectively (Table ). Nazzi et al. (00) reported that larval food may contain chemicals that influence Varroa mite reproduction. One factor that contributed to Primorsky colonies having fewer mites was the reduced number of viable female offspring per foundress. In this study, the number of progeny per reproductive Varroa mite in worker brood cells infested by single foundress of the Primorsky colonies was significantly lower than that of the Thai commercial colonies (t=., df=8, P=0.00) with the mean of and progeny per foundress (mean + standard error), respectively (Table ). The lower reproductive rate in the Primorsky colonies might be affect on the comb built by the Primorsky bees that contributed to decreased numbers of Varroa progeny and viable female offspring as in the previous report of De Guzman et al. (008). Less attractive Primorsky bee hosts in this study may also result in a reduced reproductive success among reproductive Varroa mites. The reproductive rate of V. destructor females in worker brood cells infested by single foundresses in the Primorsky colonies in this study (. progeny) was consistent with the previous report by Guzman et al. (008) that reproductive Varroa mites in A. mellifera worker brood cells produced -.7 progeny per female mite. The higher rate of progeny per reproductive mite (. progeny) was found in the Thai commercial colonies. This might be affect on the less mortality of Varroa offspring in the Thai commercial worker brood cells since, normally, a reproductive Varroa mite lays five eggs in A. mellifera worker brood cells (Martin, 00). Mite reproductive rates might be lowered if there was reduced feeding activity on the larvae or pupae by the foundress mites (Grandi-Hoffman et al., 00). Larvae movements of Africanized bees can reduce mite feeding on infested worker brood (Calderon et al., 009) and might be responsible for the low fertility rates of mites in the brood of Africanized honey bees (Ritter and De Jong, 98). The suppression of the reproductive ability of Varroa females by the host is still considered a crucial character to affect the mite s population dynamic (Fries et al., 99; Rosenkranz and Engels, 99; Harbo and Hoopingarner, 997; Correa-Marques et al., 00; Rosenkranz et al., 00). The result here showed that the number of progeny produced by reproductive Varroa mites (or fecundity) was not correlated with the number of non-reproductive mites in the colonies. Correlation between fecundity of reproductive mites and the number of non-reproductive mites was not found in the Primorsky (r=-0.7, P=0.9) and Thai commercial (r=-0.077, P=0.78) colonies. This incidence was consistent with previous reports from several researchers that the number of progeny produced by reproductive Varroa mites was independent of the frequency of non-reproductive mites in a colony (Rosenkranz and Engels, 99; Martin, 99b).

8 Kavinseksan et al. Multiply-invaded cells CONCLUSION The number of progeny per reproductive Varroa mite in cells infested by more than foundress of the Thai commercial colonies was significantly higher than that of the Primorsky colonies (t=., df=8, P=0.00) with the mean of and progeny per foundress (mean + standard error), respectively (Table ). The results here showed that the number of progeny per foundress in worker brood cells infested by multiple foundresses (-.0 progeny per foundress) (Table ) of the Primorsky and Thai commercial honey bees was lower than that of the cells infested by single foundresses (.-. progeny per foundress) (Table ). This finding was consistent with the previous reports by Fuchs and Langenbach (989) Martin (99b) Martin and Medina (00) and Mondragon et al. (00) that the reproductive rate depends on the infestation of a single brood cell; in multiply invaded brood cells the reproductive rate per female mite is significantly reduced. When A. mellifera brood cells are invaded by more than one mite, competition between offspring at the feeding site increases the offspring mortality, especially of the younger stages (Martin, 99b). Also, the mother mites in heavily infested cells show a decrease in the number of eggs laid per mite (Steiner et al., 99; Marcangeli and Eguaras, 997). In Thailand, A. mellifera was introduced in the early 90s for the first time and in 9 for the second time but did not succeed to maintain the bee until the early 970s (Wongsiri and Chen, 99). V. destructor and T. mercedesae are considered to be the most important limiting factors to the development and expansion of A. mellifera beekeeping in Thailand and tropical Asia (De Jong et al., 98; Nyein and Zmarlicki, 98). Thus, A. mellifera in Thailand (Thai commercial honey bees) and V. destructor have coexisted and evolved for about 0-0 years. This time period might be too short for the Thai commercial honey bees to develop a high level of resistant genetics to V. destructor. The Primorsky honey bees are known to have resistant genetics to V. destructor (Danka et al., 99; Rinderer et al., 997, 999, 000, 00a, 00b, 00, 00; De Guzman et al., 007, 008). The results here showed that the Primorsky honey bees are more resistant to Varroa mites than the Thai commercial honey bees. The Primorsky colonies had significantly lower percentages of infested brood cells and reproductive mites and numbers of progeny per foundress than those of the Thai commercial colonies (Table and ). Also, the Primorsky colonies had significantly higher percentage of non-reproductive mite (.%) than that of the Thai commercial colonies (.%) (Table ). It is possible that the Primorsky bees have coexisted with V. destructor more than 0 years and developed a high level of resistant genetics to the Varroa mites. The result in this study showed that the Primorsky honey bees had more suppression to V. destructor reproduction than the Thai commercial honey bees. The average percentage of non-reproductive mites in worker brood cells infested with one V. destructor female of the Primorsky colonies (.%) was significantly higher than that of the Thai commercial colonies (.%). Almost all of these non-reproductive mites in the Primorsky (9.8%) and Thai commercial (9.9%) colonies were ones that did not lay eggs. The average number of progeny per reproductive Varroa mite in worker brood cells infested by single foundress of the Primorsky colonies (. progeny per foundress) was significantly lower than that of the Thai commercial colonies (. progeny per foundress). Also, the number of progeny per reproductive Varroa mite in cells infested by more than one foundress of the Primorsky colonies ( progeny per foundress) was significantly lower than that of the Thai commercial colonies (.0 progeny per foundress). The number of progeny produced by reproductive Varroa mites was not correlated with the number of non-reproductive mites in the colonies. The average percentage of cells infested by more than one V. destructor females in worker brood cells of the Primorsky colonies (.7%) was significantly lower than that of the Thai commercial colonies (.%). ACKNOWLEDGEMENTS We are grateful to Bansomdejchaopraya Rajabhat University for financial support. We also thank Prof. Dr. Thomas Rinderer and Dr. Lilia de Guzman for their suggestions on research techniques. REFERENCES Al Aattal Y, Rosenkranz P, Zebitz CPW (00). Reproduction of Varroa destructor in sealed worker brood cells of Apis mellifera carnica and Apis mellifera syriaca in Jordan. Mitt. Dtsch. Ges. 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