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A new trap for flying intruders in the bee colony as an integral part of the modern beehive: its structure and function
Ifantidis, M. D.1*, Chatzopoulos, St.², Katikou P.1

1 Laboratory of Apiculture and Sericulture, Aristotle University of Thessaloniki, 54124, Greece
2 Inox-Form, Peloponnisou 4, 12461, Athens, Greece

Abstract
The structure and function of a new type of trap for insects as potential intruders in the bee colony, under the trade name APIBURG® is described in this paper. The trap is permanently installed under the brood chamber of a modern beehive, replacing completely the classical bottom of the hive. Preliminary data indicate an effective function of the new bottom-trap against wasps, moths, robber bees etc., without using baits, but taking advantage of the natural odors of the bee colony itself instead. It can be reasonably assumed that the new bottom-trap will be effective also against the small hive beetle (SHB; Aethina tumida). Possible uses and advantages of APIBURG® are discussed.

Introduction
The majority of the known types of traps for insects and specifically for wasps, have one or more usually conic entrances, which function as valves leading the “undesirable” insects into a tight cage specified for them (Edwards, 1980). In addition, different foods such as meat, fish, or several drinks, i.e. wine, beer, are always placed inside the cage to attract the insects through their odors. Such traps are also usually installed in places where people reside and/or work, in an attempt to avoid disturbances by wasps.

Beekeepers, especially in warm and dry climates, are interested in minimizing damages to their bee colonies by protecting them from wasps. In that case the traps are installed within or near the beeyard, preferably in the early spring in order to capture the queens of wasps. In some cases traps meant to capture hornet at the hive entrance have cones, lattices and screens that allow passage to honey bees while retaining hornets (Morse 1980).

The beekeepers are usually recommended to use baits containing insecticides in the open field (Morse 1980). This way the wasps transfer the poisoned food to their own colonies, which finally are totally destroyed. Moreover, the poisoned baits contribute to the pollution of the environment, by also injuring species other than wasps.

The present paper describes the development of a new trap to be used mainly by beekeepers in order to effectively protect their bee colonies generally against several small flying intruders in the hives all over the year, without poisoning the nests of the intruders and consequently without polluting the environment. The new bottom-trap will indirectly contribute to the minimizing of the presence of insecticides or acaricides within the bee colony, which conventionally are applied within the bee hive. So, by using the new bottom-trap the production of honey with no residues can be achieved.

Material and methods
Structure of the hive bottom-trap
The new trap bearing the trade name APIBURG® is a stainless basin (Fig. 1i Aa) having a perforated movable roof made of the same material (Fig. 1i Ba) and being tight for wasps, bees, wax moths as well as for the small hive beetle (SHB). The roof of the bottom-trap functions simultaneously as the floor of the beehive. The total weight of the bottom-trap is 3.8 kg and can sustain an additional weight of more than 240 kg.

The side-walls of the trap have entrances conic or pyramid shaped, which lead the small flying intruders into the basin under the perforated floor of the hive. In the front wall of the basin below the wooden door of the beehive, there is an additional long narrow horizontal entrance (Fig. 1i E), allowing passage to the bottom-trap especially for the wax moths and the small hive beetle (SHB; Aethina tumida) but not for bees and wasps. The hind wall of the basin is equipped with a drawer (Fig 1i Ab), which allows an easy and fast cleaning of the trap without disturbing the bee colony.

The upper protrusions at the four corners of the basin stabilize the roof of the trap and the first body of the hive. On the other hand, the lower protrusions serve the firm connection of two beehives with each other during migration, in case the cover of the hives has the same horizontal dimensions with the hive bodies.

The complementary trap
Exclusively for the wax moths and for the SHB, there is also a separate stainless trap, inserted between the wooden door of the hive and the brood chamber (Fig.1i Bb and Fig. 2). This trap is also removable for cleaning. The size of the entrance of this trap does not allow passage of bees and wasps; its hind wall is perforated but is too tight for the intruders (Fig. 2ii). Externally, the hind wall of the complementary trap is partially covered with a wooden part (Fig. 2ii A) exactly opposite to the entrance of the hive. This way the bees of the hive are able to walk on the less cold wooden surface than the metal one and therefore reach the exit of the hive without obstacles, when environmental temperature is relatively low.

As regards to the respiration needs of the bee colony, the perforated roof of the bottom-trap provides the main volume of air also during migration of the bee colonies. The complementary trap also contributes to the permanent ventilation of the hive. This way it is not necessary anymore to have an entrance ventilation slot when shutting the hive for migration.

Modification of the entrance of the bee hive
The size of the entrance in the wooden door of the beehive (Fig. 2iii) is permanently reduced to a surface of about 10 cm2. Furthermore, the common landing board is omitted.

“Baits” of the trap
In the new bottom- trap, the odors of the live bee colony itself replace the odors of the usual baits in their function.

Function of the hive bottom-trap
The effect of APIBURG® against wasps and robber bees has been tested during three consecutive years (2002, 2003 and 2004) in Argyroupolis-Kilkis (altitude 90 m), 50 km Northern of Thessaloniki, Greece (North latitude 39.5). The trap remained in its position all over the year. Five experimental bee colonies were used. One of them was placed alone, away from the other four bee colonies, which formed a group. Five other bee colonies had the common bottom of the modern hive. They were scattered among the four experimental colonies in an area of 500 m2 and served as controls regarding the possible effect of the bottom-trap on the function of the bee colony. All colonies except one were of the local bee race Apis mellifera macedonica, while one of them belonged to the black race A. mel. mellifera. The nine colonies of A. mel. macedonica were headed by sister queens. All colonies have been equalized regarding their strength and they have been managed in the same way throughout of the year. Regarding health of the experimental colonies we have systematically applied the conventional therapies for bee pathogens, by using the recommended drugs and methods for each disease.

Results and Discussion
Under the given environmental, ecological and beekeeping conditions the following insects were captured in the bottom-trap with declining frequency: worker bees, wasps, drones, wax moths and death’s head moths (Acherontia atropos). In spring 2002, an after swarm with several virgin queens was also captured in one of the bottom-traps.

Data regarding the number of captured wasps and worker bees during the three-year experiment are presented in Tables 1, 2 and 3.

Effectiveness of the trap against intruders
The data of Table 1 are obviously valid only under the specific ecological conditions, because they are strongly depended both upon the density of local wasp colonies and their strength. Wasps indeed live in so different ecological conditions all over the world. For example, the European wasp Vespula germanica (often referred to as the German wasp) has been introduced in New Zealand, Australia, South Africa, Chile, and the United states since 1950s (Matsuura 2004). It is evident that the new bottom trap of the modern beehive can be of a universal rather than a regional (Delaplane 2005, personal communication) interest at least for beekeepers.

Nevertheless, the effectiveness of the bottom-trap APIBURG® against wasps as well as against robber bees can be correctly estimated only when the events at the hive entrance are also taken into account. By observing the behavior of the flying intruders (wasps or robber bees), one can ascertain that at first they hesitate to go directly though the narrow and short entrance of a hive established on an APIBURG® bottom. Depending on the density of guard bees at the hive entrance, the intruders continue or abandon their effort to enter the colony. After some unsuccessful attempts in front of a well controlled entrance by the guard bees the intruders are finally led to the side entrances of the bottom-trap and enter in it. The majority of the intruders are attracted olfactory to the entrances of the trap and they find these entrances, without having previously visually inspected the entrance of the beehive. In any case honey bee guards do not react against wasps only by use of optical cues. As it has recently been established they recognize Vespula wasps using also olfactory cues (Wood and Ratnieks 2004).

The data of Table 2 indicate that the number of trapped bees per colony and day (150/25 = 6) under the concrete beekeeping conditions is rather negligible. In our case the bee yard was rather small and undisturbed (with no robbery). Also, from the data of Table 3, it is evident that the trapped bees per colony were 4.3 times lesser in the singly placed colony than in the case of the colonies being placed as a group. At first, these data indicate that the majority of trapped bees are foreign (robber) ones than disorientated “native” bees. This conclusion was verified when the body color of the trapped bees was also considered. Specifically in the case of the unique colony of A. mel. mellifera the black (“native”) bees of that hive constituted permanently less than 10% of the total number of the trapped bees.

It is obvious that the parameter “trapped bees per hive and day” is strongly depended upon the density of the bee colonies in a bee yard. For example, in the case of the bee yard of the Laboratory of Apiculture of the University of Thessaloniki, more than 70 bee colonies were established on an area of 150 m2 in the summer time of 2005. In this case the number of “trapped bees per hive and day” exceeded that of 50 in the bottom trap of each of the two hives equipped with an APIBURG® bottom. It must also be emphasized that robber bees are the main factor for the horizontal expansion of parasitic as well as infectious diseases (Bailey 1981, Hansen and Brodsgaard 1999)

The number of “trapped bees per hive and day” is also depended upon the season of the year in the same area. Indeed, the comparison of the data of Tables 2 and 3, reveals that the frequency of the trapped bees per colony and day was 7.6 times higher in mid- fall (150 bees/25 days = 6.00) than in late summer (39 bees/50 days = 0.78) in the given area, possibly because of the decreasing production of nectar in fall. Under such conditions, it is expected that the number of searching (robber) bees for food increases.

The effect of the trap on the life cycle of the bee colony
It could be argued that the permanent installation of APIBURG® under the brood chamber would negatively influence the bee colony, for instance, due to the low temperatures during the winter. This fear is rather unsubstantial, if one takes into account that the bee colony as a superorganism is endowed with a great ability of thermoregulation (Heinrich 1981, Southwick 1983,1991, Ifantidis 2003). The only precaution of the beekeeper who uses APIBURG® bottoms is to assure an uninterrupted contact of the winter cluster with its food stores. This can be fulfilled merely by creating conditions for thermo-insulation at the upper part of the hive (Ifantidis 2001). The ability of thermoregulation of the bee colony is practically proven also in the case of the traditional bottomless skeps used for centuries in Chalkidiki-Greece (Morse and Hooper 1985, Ifantidis 2005) and correspondingly in the case of the traditional stone hives used in the past in the area of Mani-Greece (Bikos 2004). Also, Harbo and Harris (2004) have found that after 20 days of studying the effect of screen floors on populations of honey bees the treatments showed no differences in brood production, honey consumption, or survival of adult bees.

Nevertheless, in the present experiment we have examined the possibility of a negative effect of the new trap on the development of the bee colony, if we take as a reliable indicator the annual production of honey per colony. On the basis of some rough calculations for honey production (data not shown) no differences were documented between colonies housed in hives with solid wooden floor or correspondingly with perforated metal floor. In general, the average annual honey production per hive (n=5) under the given beekeeping and floral conditions fluctuated around 15 kg, regardless of the type of the bottom of the hive. Our results are in accordance with Ellis et al (2003), who found that the production of honey per colony is not affected when the bee colony is established on a hive with a screen bottom under the condition that the entrance of the hive is 11,33 cm2. In our case the colonies were also established on perforated bottom and the entrance of the hive was about 10 cm2.

On the other hand, it was not possible to estimate the influence of the attacks of wasps against the bee colonies regarding honey production under the specific experimental conditions. It is reasonable to assume that the frequency of attacks of the wasps against bee colonies equipped with the conventional hive bottom was decreased, because the attraction of the intruders could be rather greater in the colonies equipped with APIBURG®, due to the intensive disperse of the honeybee colony odors through the large entrances of the trap. This assumption is enforced by the observation made on the behavior of A. tumida by Ellis et al (2003) who stated that A. tumida often congregated outside the colony under the screen mesh. Presumably this was in response to colony odors dissipating through the screen below the hive. For the same reason further research is needed to estimate the possible contribution of APIBURG® in the reduction of negative effects of wax moths on the development and honey production of the bee colonies. It is also interesting to note that bee colonies with screen floors had fewer (Varroa) mites than colonies with solid floors (Harbo and Harris 2004).

It is reasonable to believe that APIBURG® would also prove to be an effective means for recording the annual cycle of wasp colonies and the fluctuation of their density from year to year in a specific area as well as for monitoring of the seasonal and daily migrations of A. tumida, beyond its many practical advantages.

Advantages of the APIBURG® for beekeeper

Acknowledgements
We would like to thank Mr. Donat Waltenberger from Mindelheim, Germany for supplying the queen of Apis mellifera mellifera. We would also like to thank Mr. Sotirios Georgantas for the artwork figures.

Bibliography

flying intruders 1Table 1. Number of captured wasps in the bottom-trap of the experimental bee colonies (n=5),
during the late summer and early fall of 2002, 2003 and 2004 in Argyroupolis, Greece (latitude 39.5, altitude 90 m).

flying intruders 2Table 2. Average number of wasps and worker bees captured in the bottom-trap of the
experimental bee colonies (n=5), in mid-fall of 2004 in Argyroupolis, Greece (latitude 39.5, altitude 90 m).

Table 3. Number of trapped bees per colony in bee hives equipped with an APIBURG®, during summer days of 2004

Figure 1

 


Figure 2

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