When can bumblebees be considered dangerous

behavior

Social behavior

Bumblebees can be described as "primitive eusocial" wild bees: They do not live individually, but in peoples or states that always consist of two generations: the queen and her daughters (workers) and sons (drones). The insects have developed a division of labor: some of the sterile females are exclusively foragers, others as "stick bumblebees" are responsible for building, maintaining (cleaning honeycombs, feeding larvae, etc.), ventilating and defending the nest and feeding the larvae; a small, privileged group of workers takes care of the queen only, in order to eventually oust her and lay unfertilized drone eggs themselves. Drones only have one job: to mate the young queens.
The queen of a state is the most flexible: if she has to work as a forager and hive bee in the spring like a solitary bee, she soon only lays eggs and builds the egg containers half-finished, but can, if necessary, resume work at any time. By giving off a certain scent, she prevents her daughters from laying eggs themselves. Only the young queens partially survive the winter and found new colonies in the following spring; these are always annual in our latitudes, so they die in autumn. More on reproduction on the next page

Aggressive behavior

Bumblebees are amazingly peaceful. Perhaps it is precisely because of their larger appearance and strength in relation to other flying insects that they often make active confrontation unnecessary, at any rate they are not prickly, and most species allow a curious person to do their thing, who carefully opens and looks at their nest. On the other hand, they do defend themselves when they feel seriously threatened: a loud hum of the entire people with vibrating wings is a clear warning signal to potential attackers. If a single bumblebee sees a specific attacker approaching, it raises one or two outstretched legs on the relevant side of the body to ward off the danger. If it is finally physically attacked, it stings: Anyone who accidentally or deliberately presses a bumblebee must expect the same consequences (harmless for healthy people) as a honeybee sting; a wasp that invades a bumblebee state, on the other hand, accepts death.

Bumblebees behave strangely indecisively towards their worst natural enemy: the wax moths. At least initially it would be easy for the sturdy insects to bite or stab them to death; the helplessness of their victims can hardly be adequately explained by the web of moths. Obviously, bumblebees in their evolution have so far had too little time or pressure to survive to develop an effective defense strategy.

Nest and flight times

A bumblebee queen - like her workers - is mostly in the nest. In this way, they reduce their energy consumption and avoid dangers that could mean the premature end of their state. Measurements by a bumblebee researcher with a Photoelectric sensors have shown that a queen flies out an average of 13 times a day before her first brood hatches. Most of the collective flights take place in the afternoon and into the early evening, and in the mornings, an average of four excursions were recorded for a bumble bee queen. Their duration is 5–15 minutes, longer absences are very rare and probably due to the weather. Temperature measurements in the nest have shown that the queen is in motion almost continuously even at night: at the sensor in the immediate vicinity of the brood comb, the difference between presence and absence was up to 15 Kelvin or degrees!

The flight of the bumblebee

When searching for food, bumblebees do not fly at their maximum speed of around 20 km / h: In order to be able to recognize the flowers, they reduce their speed to up to 90 meters per hour. At this slow-motion pace, bumblebee eyes and bumblebee brain do amazing things:
Two "neural channels" recognize the flower size and color separately: the first reports the discovery of a flower to the brain after five thousandths of a second, but not its color; it is therefore relatively imprecise. The second channel enables bumblebees to see colors; it works more slowly but more precisely.
Both channels are significantly faster than human image processing: In comparison, they would have to fly four times slower over a meadow in order to be able to recognize its flowers.
(Source: Spaethe, J., J. Tautz & L. Chittka (2001) in: Proceedings of the National Academy of Sciences (PNAS), Vol. 98, No. 7, pp. 3898-3903)

Foraging

Like honey bees, bumblebees collect pollen and nectar. Compared to the domesticated competition, however, they have three advantages:

    Bumblebees collect up to twelve times more nectar per insect and visit up to five times more flowers. Your collecting bladder in your abdomen (Abdomen) can absorb so much nectar that a bumblebee can double its weight. The honeybees only perform better per colony because of their large head count, which is artificially encouraged by beekeepers. Because of their size and strength, as well as their weight and body structure (due to their longer proboscis), bumblebees also exploit flowers that are not accessible to honey bees. Many plant species can therefore only survive with bumblebees (Symbiosis). Bumblebees also fly in search of food when it's cold (from approx. 4 ° C) - an adaptation that allows them to have cooler times of the day (morning and evening), cooler seasons (early spring) and cooler, i.e. H. opens up more northern latitudes.
 
Bombus argillaceus W. at Lamium album Salzburg, Muhr (1200 m above sea level) (ne) Bombus lucorum at Salix nigricans · Salzburg, Zell / Wallersee (ne)
  • In order to be able to collect as much protein-containing pollen as possible, bumblebees have developed a special technique: by vibrating at high frequencies (recognizable by its bright sound) on or in a flower, they shake the pollen from the pollen carriers into their fur; there it is moistened and taken up by the legs in order to be collected and transported in the "panties" (collecting hair) of the rather broad hind legs.
  • In order to be able to empty flowers with a deep calyx, many bumblebees have a rather long trunk, which is good for the common bumblebee (B. pascuorum) can be observed; The Eisenhuthummel has the longest (B. gerstaeckeri). Other, short-nosed species use a trick: nectar robbery. These "primary nectar predators" bite a hole at the base of the flower and thus find the short and direct route to the nectar, which is then conveniently used by long-nosed bees ("secondary nectar predators"). Incidentally, only species of the subgenera were noticed as primary nectar predators in Europe Alpigenobombus (so B. wurflenii) and Bomb(cryptarum, lucorum, magnus, terrestris).
  • In order to be active in spite of low outside temperatures, bumblebees, which as insects are actually cold-blooded, can generate their own warmth: by trembling their strong flight muscles, they can especially thorax With the wings disengaged, heat up to the point where the temperature of 30–40 ° Celsius required for flying is reached. Her unusually thick fur protects her from excessive heat loss.
    Of course, this method means a loss of energy, so it requires sufficient energy generation, but bumblebees have also learned how to save energy: If it is possible without any problems, they crawl from flower to flower instead of flying. A hairless "brood spot" on the underside enables the stick bumblebees to effectively give off heat to the brood.
  • While 30% of the nest-building solitary bees specialize in the pollen of certain plant families, genera or even species (as oligolectic), our bumblebees generally use all flowers whose nectar and pollen they can reach - with one exception: Bombus gerstaeckeri, the "Eisenhuthummel", is apparently in Eisenhut stocks (Aconitum sp.) bound.

Bumblebees that fly out for the first time know where to go, they don't need to learn. But they have to learn how to make use of the respective flower, since flowers are built quite differently.

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