Abstract: This study was conducted to investigate the effects of heating and ventilation devices mounted to insulated and wooden bee hives on some physiological characteristics of honeybees. The average number of frames in groups Control (C), Heated (H) and Heated-Fan (HF) were 15.14±4.73, 16.98±6.05 and 18.74±7.34 colony^-1, respectively. The average brood area for the colonies in groups C, H and HF were 4270.64±302.12, 4819.00±348.50, 5270.00±344.33 cm², respectively. The values of flying activity in groups were 74.79±19.80 in C, 85.36±27.34 in H and 101.43±16.78 in HF. Honey yields in groups C, H and HF were 14.61±1.71, 20.63±1.99 and 28.14±2.97 kg colony^-1, respectively.

INTRODUCTION

Factors of external ambient and internal hive conditions are very important on the productivity of honey bees (Cetin, 2004). Beehives conditions can be more comfortable for honeybee colonies using devices such as fan and heating. Although, many studies have been studied on honey bees in the world, the numbers of conducted researches on the effects of factors such as internal hive temperature and humidity on honey bees are not quite extensive.

Temperature is one of the most important internal hive conditions. A high and constant brood temperature makes brood nest period shorter and reduces the rate of emergence in death or defective brood in social insects such as honeybee (Apis mellifera), vespa crabro (Vespinae) and bumble bee (Bombus sp.) (Seeley, 1985). During flight, the rather large flight muscles create heat, which must dissipate to brood area (Esch et al., 1991). The brood nest needs temperature of 30-36°C to develop the brood (Seeley and Heinrich, 1981). Nest heating has an energetic cost: when ambient temperature drops from 28-17°C, the metabolic rate of a bee colony rises from 7-19 watt kg^-1 (Southwick, 1982). In order to minimize winter losses of bee colonies by improving hive microclimatic conditions, various trials were conducted in the United States (Owens, 1971; Detroy et al., 1982), Germany (Himmer, 1926), Norway (Villumstad, 1974) and in other countries. Researchers studied the effect of hive insulation on heat conservation inside the hive, reducing honey consumption from about 21-25% (Detroy et al., 1982), to up to 43% (Himmer, 1926).

Honeybees keep inside the hive atmosphere under livable conditions by fanning their wings. These behaviors of honey bees keep temperature and humidity within a certain limit. Bees consume honey to rise inside the hive temperature in winter (Hazelhoff, 1954).

In this research, we studied the impact of the internal hive temperature and humidity values of heating and ventilation devices mounted to beehives and their effects on physiological characteristics of honey bee colonies.

MATERIALS AND METHODS

A total of 42 Caucasian crossbreed honey bee colonies were used in the present study. Colonies were initially equalized to contain a similar amount of brood (five frames containing nest brood), adult bee population (ca. 9 frames covered with bees) and food stores. Colonies were divided into 6 groups as follows: (W-1) control group, (W-2) heated-wooden beehive adjusted to 21°C, (W-3) heated-fan wooden beehive adjusted to 21-34°C, (I-1) Control group in insulated beehives, (I-2) heated- insulated beehive adjusted to 21°C and (I-3) heated-fan insulated beehive adjusted to 21-34 °C (Table 1). In this way, application groups of W1-I1, W2-I2 and W3-I3 were consisted of control group, Heated (H) and Heated-Fan (H-F), respectively.

A 12 V, 0.68 A, 4 W and 8 cm diameter ventilation- fans were used to ventilate beehives. The spin speed of fans was set up as 2.5 km h^-1 to provide air circulation. A 6 m resistance wires (220 V, 180 W), which was placed in bottom of the hive, was covered with silicon to provide an isolation for heating of the hives.

Table 1:	Experimental groups

In order to eliminate the negative magnetic field effects on honey bees, the wires were covered with a thin sheet metal. A termohigrometre was used to determine daily maximum, minimum internal hive temperature and relative humidity in the bee yard.

A digital thermostat which is connected to double contactors and attached to the sensor probe was used to observe brood nest temperature. When, the thermostat reached at adjusted low temperature (21°C), the heater resistance started to run but it was turned off when it was just 21°C. When internal hive temperature rose to excessive levels (34°C), inside the hives was ventilated by fans and when it dropped to certain temperature the fan was turned off. The resistance was activated or inactivated by thermostats with a single contactor used in groups W-2 and I-2.

On 5th June 2007, colonies were equalized for 9 frames covered with bees and 5 combs of brood/colony to observe adult bee development. From this equalization till honey harvest (25 August), the number of frames covered with bees was determined 30 days interval as a measurement of adult bee development. In the same period, measurements of worker brood area were determined by measuring capped brood to the nearest cm² using PUCHTA method at the beginning of every month (Fresnaye and Lensky, 1961).

In order to determine weight gain during nectar flow, all colonies were weighed at the beginning (June 20) and end of nectar flow (August 5). A flight activity was determined in one colony randomly selected from experimental colonies. For this, number of flying bees was observed for 60 sec running, 7 times 10 days interval before noon at 10:00 am (Genc et al., 1999).

Honey was harvested from only supers of each colony. All combs were marked with its own hive number during the harvest. All combs were weighed before and after honey extraction and the difference in between were recorded as honey yield (Genc and Aksoy, 1993).

The present study was designed with 3-way repeated measures and 7 honey bee colonies in each repeated measures (Gorgulu and Sahinler, 2006). SPSS version 13 packet program was used to do statistical analysis. Duncan (1955) test was used to determine the significant differences between group means in an analysis of variance setting.

RESULTS AND DISCUSSION

The average maximum and minimum internal hive temperature and humidity values were given in Table 2. The average maximum and minimum temperature and humidity in wooden and insulated hives was recorded as 37.09±3.42°C, 22.00±2.07°C, 61.97±10.65%, 24.83±3.54% and 35.98±2.78°C, 22.74±2.03°C, 64.18±10.18%, 25.00±4.19%, respectively. The best results were obtained in group H-F with regard to maximum and minimum internal hive temperatures. This result indicate that internal hive temperature is not allowed to go over and under a certain limit by fan that is mounted on the top of hive and resistance wires placed in bottom of the hive.

Studies have shown that the temperature inside uninsulated wooden beehives differs little from ambient temperature (Owens, 1971). Heinrich (1993) reported that there are some temperature effects on honey bees and the bees' activities to control temperature in a beehive that does not have apparatus designed to cool the beehive artificially in hot weather.

Experimental colonies in the current study reached to highest level towards to end of nectar flow by exposing a regular improvement with regard to adult bee population. The best results in adult bee population were obtained in H-F. The average adult bee population with regard to hive types was 17.46±6.59 in insulated beehives and 16.44±5.96 in wooden beehives (Table 3). The results of adult bee population in group H-F was found higher than previous trials carried out by different researchers (Guler, 2000; Sahinler and Kaya, 2001; Dodologlu and Genc, 2002; Dodologlu et al., 2004).

The brood area growth and flight activity was higher in group H-F than those of other groups. Brood area growth and flight activity in insulated hives was found higher than wooden beehives. According to results, obtained in the present study, the best period in brood growth was during nectar flow session. This result is similar to the results obtained by Genc et al. (1999).

Table 2:	Maximum and minimum internal hive temperature and humidity
a,b,cMeans in each column followed by the same letter are significantly different (p<0.05)

Table 3:	Brood area growth and the number frames covered with bees
*Means in each column followed by the same letter are significantly different (p<0.05)

Table 4:	The results of weight gain during nectar period (kg colony-1), number of foraging honeybees and honey yield (kg colony-1)
*Means in each column followed by the same letter are significantly different (p<0.05)

The results of average brood activities in current study are higher than the results reported by numerous researchers (Guler and Kaftanoglu, 1999; Karacaoglu et al., 2003). Regarding to flight activity, the results obtained in the present study was higher the findings recorded by Dodologlu et al. (2004) but lower than those reported by Dodologlu and Genc (2002). The highest weight gain during nectar flow period was recorded also in H-F. On the other hand, the highest and lowest weight gain during nectar flow was obtained in I-3 and W-1, respectively (Table 4). However, these findings are lower than the results obtained by Dodologlu and Genc (2002) and Dodologlu et al. (2004).

Since, internal hive temperature and humidity was suitable, honeybees housed in HF had many foragers and they carried more water and nectar compared to other colony groups. Likewise, the highest honey yield (28.14±2.97) was recorded in group H-F and there was a significant difference (p<0.05) between application groups (C, H and H-F). Among hive types, the highest honey yield was obtained in insulated hives and this result was higher than a previous study reported by Chaudhary (2001) and lower than the findings by Wineman et al. (2003).

CONCLUSION

Consequently, there are little technologic researches about internal hive comfort. In the current study, significant differences were found between applications and control groups in favor of applications. Internal hive temperature and humidity and ventilation of the hive plays very important role on honey bee behaviors. We think that the results contained in the present study could give fundamental information to beekeepers and technologic researches in beekeeping in the future.