Η συμπεριφορά των μελισσών στις φωτιζόμενες κυψέλες
Α. Θρασυβούλου, Σ. Στυλιανού και X. Χατζηαντωνίου
Εργαστήριο Μελισ/μίας - Σηροτροφίας, Θυρίδα 277, Αριστοτέλειο Παν/μιο Θεσ/νίκης.
Το μπροστινό τοίχωμα της κυψέλης αντικαταστάθηκε με δύο τζάμια διαστάσεων 15 χ 30 εκ. τα οποία απείχαν μεταξύ τους 8-10 χιλιοστά. Τους ζεστούς μήνες, τοποθετήθηκε πάνω απο το τζάμι λεπτή λαμαρίνα πάχους 0,3 και μήκους 15 εκ. mm σε κλίση 45 μοιρών ώστε να εμποδίζεται η είσοδος των ηλιακών ακτινών και η υπέρμετρη αύξηση της θερμοκρασίας μέσα στην κυψέλη. Τα πειράματα έγινα απο τον Μάιο του 1990 μέχρι τον Οκτώβριο του 1991.
Χρησιμοποιήθηκαν 6 μελίσσια στις κυψέλες με τζάμι (φωτιζόμενες), και 6 σε κανονικές (μάρτυρες). Όλα τα μελίσσια ξεκίνησαν περίπου με τον ίδιο αριθμό μελισσών, την ίδια ποσότητα γόνου και τροφών και είχαν αδελφές βασίλισσες της ίδιας ηλικίας.
O σφραγισμένος γόνος μετριόταν κάθε 13 ημέρες απο το Μάιο του 1990 μέχρι τον ΟκτώΒρη του 1991 (Παππάς 1991) . Η παραγωγικότητα βρέθηκε έμμεσα απο την ταχύτητα που οι μέλισσες κατανάλωναν μια συγκεκριμένη ποσότητα ζαχαροζύμαρου (Milne 1977) και άμεσα απο την παραγωγικότητα των μελισσιών. Η επιθετικότητα εκτιμήθηκε απο τον αριθμό των κεντρισμάτων που δεχόταν ένα δερμάτινο μπαλάκι που αιωρείτο για ένα λεπτό μπροστά στη είσοδο της κυψέλης ίStört, 1974). Εγινα επίσης μετρήσεις που αφορούσαν την υγιεινή συμπεριφορά των μελισσών και στηριζόταν στην ταχύτητα με την οποία οι μέλισσες απομάκρυναν κάποια συγκεκριμένη ποσότητα νεκρού γόνου (Taber, 1982).
Διαφορές στην παραγωγή γόνου στις δύο ομάδες τους πρώτους μήνες εγκατάστασης (6/6 έως 5/10) ήταν στατιστικά μη σημαντικές. Απο τον Οκτώβριο όμως και μετά η εκτροφή γόνου στις φωτιζόμενες κυψέλες ήταν εντονότερη, στατιστικά σημαντική και καθοριστική για την μετέπειτα εξέλιξη των μελισσιών. Απο τον Οκτώβριο μέχρι τον Φεβρουάριο της επόμενης χρονιάς τα μελίσσια στις φωτιζόμενες κυψέλες είχαν εκθρέψει 13782 μέλισσες ενώ στις κυψέλες μάρτυρες 3155. Η διαφορά αυτή έδωσε προβάδισμα στα μελίσσια των φωτιζόμενων κυψελών που Βγήκαν απο τον Χειμώνα δυνατότερα, ανεπτύχθηκαν γρηγορότερα την Ανοιξη και τελικά έδωσαν διπλάσια απόδοση σε μέλι .
Η μεγαλύτερη παραγωγή γόνου στις φωτιζόμενες κυψέλες αποδόθηκε στην αυξημένη δραστηριότητα που είχαν οι μέλισσες σ'αυτές καθώς επίσης και στις υψηλότερες θερμοκρασίες που κρατούσαν τους χειμερινούς μήνες.
Ενώ την Ανοιξη και το Καλοκαίρι επαναληπτικές μετρήσεις της επιθετικότητας έδωσαν αντικρουόμενα αποτελέσματα, το Φθινόπωρό οι μέλισσες στις φωτιζόμενες κυψέλες έδειχναν μικρότερη επιθετικότητα.
Οι μέλισσες στις φωτιζόμενες κυψέλες απομάκρυναν πολύ πιο γρήγορα την ίδια ποσότητα νεκρού γόνου, και κατανάλωναν μεγαλύτερες ποσότητες τροφών απο τις μέλισσες των κανονικών κυψελών. Τους Φθινοπωρινούς μήνες τοποθέτησαν πρόπολη μεταξύ των κυρηθροφορέων.
THE EFFECT OF FRONT-GLASS WALLED HIVES ON HONEYBEE
REPRODUCTION AND BEHAVIOUR*
THRASYVOULOU1, P. CHARONIS2, Sofia GOUNARI1, M. KONTESIS2
laboratory of Apiculture-Sericulture School of Agriculture, Aristotle University, Thessaloniki, Greece
2Higher School of Enginering, of Peraeus, Greece
Twenty colonies of honeybees were hived in standard hives that had their front wall replaced by a double glass so that the light freely penetrated inside the hives, and were compared with colonies in regular standard hives used as controls. Colonies in FGW hives were warmer during the cold months of the year, reared more brood and collected more honey than the colonies used as controls.
Key words: Honeybees/glass wall hives/honey and brood production/aggressiveness/propolis/ Greece
Honeybees overwinter in their nest in an active state forming a cluster where temperature is regulated. The cluster shifts its position to other combs to obtain honey for food, unless it is held to one location by brood. Heavy losses may occur during prolonged period of severe cold when the cluster can not expand to honey stores. Anything which would elevate temperatures high to allow the bees move to new honey stores and to fly outside for cleansing flights should enable colonies to successfully overwinter.
The heat that is derived by a bee-hive from direct sunshine was proposed as particular important practice to resolve this problem. WALTON (1974) used the solar energy by clamping a framed panel of glass on the outside of a hive. He found that the temperature have risen up to 4oC above ambient. A similar device was used by SHAW (1981). GARY (1979) constructed a solar collector by using plastic front, black insulation back and aluminum cans filled with water on the ground. TAYLOR (1981) patented a solar heating panel that can be put below the cover of the hive.
We approach the idea of adding solar heat to a hive by replacing the front side of hives with a double glass (FGW-hive) to take advantage the unique properties of glass which permits the free passage of high frequency waves and obstructs the passage of low frequency waver. Besides overwintering we investigated the colony reaction into these hives, their buildup response during honeyflow and their behaviour and productivity during the warmer period of the year.
Materials and methods
Twenty colonies were established into Langstroth hives, which had their front wall cut off and replaced by a double glass of 15 x 30 cm (FGW). The two glasses were at a distance of 8-10 mm apart. Twenty colonies were also installed into normal Lngstroth to derve as controls. During the warm months (April throgh September) a sunbonnet was placed above the glass with an inclination that would prevent the direct penetration of sunlight rays in to the hive.
All colonies started with three combs’ populations and received newly emerged and naturally inseminated sister queens of Apis mellifera macedonica. To hold the bees into their new hive a frame of brood was put for 3-2 days in them. The number of bees in each hive was estimated visually on the day preceding each test with the assumption that 3000 bees were covering one comb.
All colonies were treated in the same way. They were opened on the same day and were examined for brood diseases, availability of space for brood rearing as well as food storage. Combs with new foundation were given to colonies that needed more space. The only disease that was treated with a chemotherapeutic agent was Varroatosis which was controlled with a fluvalinate based drug during autumn. Sugar syrup was only fed to colonies that had no sufficient quantity of honey for successful aver-wintering.
The area of brood was measured every 13 days from June 1992 to September 1993 by means of a clear acrylic plastic (Plexiglas) grid (2x2 cm), estimating that 4.28 cells occupy 1 cm2.
The temperature of each hive was measured by a CR-10 fully programmable datalogger (Campbell Scientific Inc.) communicated with computer equiped with telecommunication mode (Maxmodem 2400). In each hive three thermocouple installations recorded every half hour the temperature at front (behind the double glass wall), at the middle (brood area) and at the back of the hive.
The colonies were fed candy and the daily consumption was measured as an indication of their productivity. At the same time, the colony’s productivity was estimated by the total honey production during the period of study.
Honeybees’ aggressiveness was measured according to STORT (1974), by jerking a black leather ball in front of the hive entrance for a period of 60 seconds and counting the number of stings on it. For every test, a new ball was used for each colony in order to avoid errors caused by alarm pheromones that bees may have left on the previous used ball. All the experiments were conducted at the University apiary of Aristotle University of Thessaloniki, Greece between May 1992 and November 1993.
Results and discussion
Figure 1 shows the curves of total brood production of the two experimental groups from June 1992 to September 1993. During the four first months of the experiment the differences in brood production between colonies in FGW hives and controls were not significant (P>0.05).
Fig. 1 - Brood production of colonies in FGW and control hives
during June of 1992 and September of 1993
During winter months colonies in FGW hives had more brood than controls. It was calculated that between November and February, the average brood production of FGW colonies was 13800±546 cells while that of controls was 3100±189 (significant at P<0.05). The additional bee population FGW hives was important for wintering, as well as for the performance of the colony the following year. As it is shown by numerous researchers (reviewed by RIBBANDS, 1953 and WINSTON, 1987) worker bees that emerged in winter, have a rich fatty tissue and live much longer than spring-bees. These longer-living bees overwinter more successfully and support colony survival in early spring when colonies lose a large portion of their population and the need for food collection is acute. Colonies in FGW hives with the important advantage of having more winter bees appeared with bigger and stronger populations in spring. Thus, 41800±2035 brood cells were counted in FGW colonies between March and July of 1993, compared to the 8600±4720 produced by control colonies (significant at P<0.05). Subsequently the larger population of FGW-colonies, thus the stronger beehives, results in faster development. This was expected, since the more the population is of a colony, the more the queen laying and likewise, and the more the brood rearing is (FARRAR, 1986).
The greater brood production in the FGW hives was probably due to the higher temperatures that prevailed during winter. For the sake of simplicity table I shows the temperatures’ readings at the front side of the hives, for four randomly selected days during a period of four months (December-March). Middle temperatures were greatly affected by the cluster temperature. During the entire day, temperatures in the FGW hives were higher than controls. Significant differences were found in sunny days from 09.00 to 16.00 and in all days between 11.00 to 14.00.
Temperatures (oC) in the front side of the experimental hives between 08.00 and 19.00 hours for four different days
It is difficult to estimate the productivity of a colony due to the fact that it is affected by many different factors, such as food abundance, weather conditions, colony strength, presence of enemies, diseases etc.
Fig 2 - The daily consumption of candy by experimental colonies
The daily candy consumption was used to indicate colony’s productivity (Fig. 2). During the first months of the experiment the differences were not significant. The colonies of the FGW hives consumed a greater amount of candy during winter months, probably because of the presence of the brood. The differences in the following months were steadily becoming more significant. To determine whether the greater consumption of candy by the FGW hive honeybees was due to their larger population and not to the experimental procedure, the population of the two experimental groups should have been equalised. However, this was not carried out because by doing so, the experimental procedure would have changed.
More information on the productivity of the two groups is given by the total honey production (Table II). The difference in the average production of 1992 was not significant. However, the production of colonies
Means with different letters are significantly different from other (P<0.05) according to t test.
in the FGW hives was almost double during the second year compared to controls. The higher honey production of the colonies in the FGW hives was attributed to their faster development during spring and their larger populations during blooming period.
Aggressiveness was estimated in three different dates during the experiment. It was found that the average number of stings on each leather ball was lower in colonies of the FGW hives, compared to control group (Table IN). However, significant differences were found only in November counting. A large variation was observed among colonies belonging to the same group as indicated by the high coefficient of variation (cv%). This does not allow any conclusion regarding differences in the aggressiveness of the two groups. Results showed that some colonies in FGW hives were much more aggressive than controls and vice versa.
One of the factors that influences the aggressiveness of honeybees during manipulations, is the visual stimulation they receive from their sudden exposure to sun light, when the hive is opened. This sudden change does not occur in colonies of FGW hives which by providing continues light, create less disturbance and thus less aggressiveness. On the other hand, the method used to estimate the aggressiveness may give false results since the continuous oscillation of the leather ball in front of the FGW hives was visible by the bees inside the hive while in the controls this didn’t occur. The increasing aggressiveness during the autumn months was probably due to low ambient temperatures.
All colonies of FGW hives during the autumn months seemed to collect more propolis. The honeybees of these colonies deposited a heavy layer of propolis in the area between the support bars of the frames at the front side of the hives, just behind the glass, only during autumn months (Fig. 3). This large amount of
Fig. 3 - Bees put propolis between the front support bars of FGW hives
The replacement of the front-side of standard hives with a double glass frame, made the honeybees more active and reared more brood during the months with low temperatures. These colonies entered into winter with young populations that tolerated better the adverse conditions of winter, developed faster during spring and produced more honey than controls in normal standard hives.
We thank the students Stilianou S., Hatzantonis C., Halkia N., Kasapaki M., Stagaki K., and Kalt- souda A. for their help in collection of the data. Thrasou K., and Harizanis P. made valuable suggestions and improved the paper.
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