I am going to post here a message on honeybee-swarms, that I actually want to see posted on BeeSource P.O.V. list, which is "more sophisticated", I mean only in terms of dealing with scientific issues.
I sent the message to Barry, for his evaluation. However, since I now realize, I have to wait for him to come back from his Honeymoon, to even look at the message, I decided to post it here, in the meantime. Couldn't do any harm. But I don't want to become involved in any endless debates about it. So, anyone who has reservations, or points of criticism, about this post, is welcome to express them. But, I do not intend to respond.
Also, for some reason, the message came out in fonts of different sizes. I do not know how to fix that. So I shall leave it "as is". Here is the message:
Note a very recent publication in ANIMAL BEHAVIOUR, 2006, 71, 161171 doi:10.1016/j.anbehav.2005.04.009
How does an informed minority of scouts guide a honeybee swarm as it flies to its new home?
MADELEINE BEEKMAN, ROBERT L. FATHKE & THOMAS D. SEELEY.
The authors posed the question of how the swarm knows in which direction to fly, when only 5% of the bees, i.e. the nest-scouts who had visited the new nest-site know where it is? The study used man-made swarms, and prospective nest-sites in the form of small wooden-hives, baited with one empty (apparently used) comb, and a lure made of the major components of Nasanov-glands secretion. The authors tested the vision hypothesis, (the possibility that the scouts visually guide the swarm in the right direction by fast streaking through the swarm, actually in the upper part of the swarm), vs the olfactory hypothesis (the possibility that the scouts guide the swarm by emitting odors from the 2 Nasanov-glands on their abdomen, so that this results in an odor-gradient in the direction of the new nest-site). To test the olfactory hypothesis the authors used swarms where all the bees had the openings to their Nasanov-glands sealed. The study showed that the treatment did not interfere with the ability of the swarm to fly quickly and directly to the new nest, compared to control-swarms with unsealed glands.
It is well-known that the scouts expose their Nasanov-glands once the swarm reaches the new nest-site, and that the odors from the exposed glands aid the swarm in entering the new nest. The results of the study, however, led the authors to discard the olfactory hypothesis, as far as guiding the swarm in flight is concerned. The vision hypothesis also poses problems, because the "streakers" streak in the direction of the new nest (for stretches of about 30 mm.), at a speed of about 10 m. per second, which is the fastest speed a swarm in flight achieve . The swarm achieves this maximum speed only gradually, but the "streakers" do not increase their streaking speed; which means that they do not fly faster than other bees in the swarm, once the swarm achieves maximal speed, so how could the streaking guide the swarm, when the swarm has already achieved maximum speed?
The authors are, therefore, still faced with a mystery. There is, however, a very simple solution to the problem, because the authors, which the authors were unable to find because they failed to pose the right wedded to the honeybee "dance language" (DL) hypothesis. This is not surprising at all, since the
senior author, Thomas Seeley, has been known for years as a staunch DL supporter.
The first one to discover that nest-scouts dance in the swarm, and to study their behavior, and the behavior of the swarm, was Martin LIndauer, v. Frisch's best known former student and collaborators, and his work is, indeed, cited by the authors. LIndauer has naturally been a staunch DL supporter. V. Frisch took it for granted that food-foragers decide when to dance, depending on the quality of the food, and the need for food in the colony. He knew that foragers never dance in the absence of dance-attendants, but assumed that the foragers know ("instinctively", or otherwise), that they should not waste time and energy to dance unless they have an audience prepared to receive the spatial information contained in the dances, about the site visited by the foragers. (See v. Frisch's 1967 book.)
By the same token, Lindauer naturally took it for granted that nest-scouts also decide when to dance, depending on the quality of the prospective nest they found, and that other swarm-mates who attend scouts'-dances then find the site by using the spatial information contained in the dances. The swarm may have different groups of bees, where each group "advertises" a different site in dances. But eventually all dancing scouts end up advertising one and the same site, apparently the best site found by any of the scouts.
Seeley, T. D. l(1977). Measurement of nest cavity volume by the
honeybee ( Apis mellifera ). Behav Ecol Sociobiol 2:201227
Seeley TD, Buhrman SC (1999) Group decision making in swarms, eventually studied how nest-scouts evaluate the size of the cavity they find.
He used apparently wooden, cylindrical boxes of various sizes, and found out that when a nest-scout enters such a box, it crawls around the circumference of the base, and that the scouts tended to dance more often for his boxes that had a longer circumference of the base (which meant also larger base, and a larger volume of the cavity).
He concluded that the scouts decide whether to dance, or not, based on their assessment of the volume of the cavity, and that they determine the volume of the cavity by determining the area of the base, which they achieve be measuring the circumference of the base.
To determine the length of that circumference by crawling along its length, requires a counting ability. There is, however, no evidence, and , therefore, no reason to believe that honeybees can count at all.
Apart from that, as I pointed out in ABJ (2000), vol. 140(1), Jan. pp. 12-13, the size of an area cannot be determined from the length of its margins. The size of the area enclosed within margins of a specific length is maximal, when the area is round, but may also be very small, as long as it leaves a honeybee enough room to crawl around the margins. Natural cavities, of course, do not occur in the form of perfect cylinders, let alone perfect cylinders of the same height as that used by Seeley..
I also pointed out that nest-scouts would not stand a chance of finding the few natural cavities (in the trunk of a tree in the woods), that are appropriate for a nest, if they were to simply examine just any tiny hole out of the myriad of tiny holes that exist in their natural environment. The scouts must, therefore, be attracted to specific tiny holes, by the odors those holes have, which the holes share with odors the scouts had learned to associate with a nest. In nature such cavities, often resulting from a lighting-strike, have the odors of "wounded" wood. Seeley's cylinders probably attracted the scouts by wood-odors. Then, if the base had a longer circumference, the scouts , naturally, took longer to crawl along the circumference, which would have resulted in their spending a longer period of time inside the cylinder, and, thus, adsorbing onto their bodies a higher concentration of the attractive odors in the cylinder.
Other factors, such as alien odors which repel the scouts, temperature and light-intensity, winds, inside the cavity, undoubtedly also play a role in the amount of time nest-scouts spend inside a cavity they find. .V. Frisch (in his 1967 book,) had, however, already noted that odors may play a role in attracting nest-scouts. But Seeley completely ignored that.
Honeybees (whether foragers, or nest-scouts), never decide whether to dance, or not. The dance results from an escape by bees carrying attractive odors, from hive-mates, or swarm-mates, who chase after them, after being attracted by the odors such bees carry. In the case of successful nest-scouts, some swarm-mates are attracted by the odors the scouts carry on their bodies, from the cavity they found; which are the odors that attracted the scouts to the cavity in the first place. Some of the dance-attendants then find the same cavity, but they do so by use of odor alone all along. The odors they carry back to the swarm then attract other swarm-mates, and the new bees that found the cavity, thus, become additional scouts that "advertise" that cavity.. Swarm bees very gradually come to prefer the scouts that carry more attractive odors. The scouts that carry less attractive odors are, thus, not chased any more, and, therefore, do not dance either. They may themselves be attracted by the odors carried by the scouts that bring back to the swarm more attractive odors, and eventually find the cavity visited by the scouts that bring in the most attractive odors. This is how a "consensus" is reached, where there is only one large group of nest-scouts, all advertising one and the same cavity.
Bees in a swarm are attracted visually, as well as by odors, to other swarm-mates, as well as to odors from the queen (which most of them cannot see). This is how the swarm keeps together. Swarm bees are, however, also attracted by the odors nest-scouts carry on their bodies.
It is these odors, which are adsorbed onto the scouts' bodies, and gradually wash off as the scouts fly with the swarm, that create the odor-gradient that leads swarm-bees in the direction of the cavity. The scouts expose their Nasanov -glands only after they land at the entrance to the cavity. I have never seen any report by anyone who saw them expose those glands while flying with the swarm. The scouts attract swarm-mates only by the odors adsorbed onto their bodies, and sealing the Nasanov-glands of all the bees in the swarm, therefore, should not have any effect on the swarm's-flight to the new nest; as the study showed.
The authors knew they had deliberately used in their prospective nests odors that attract nest-scouts. However, the possibility that such odors, that adsorb onto the bodies of scouts that visit such a prospective nest, are the odors that also attract swarm-mates, which results in the dances of nest-scouts, and then, when there is a large enough number of scouts which all carry the same attractive odors, which suffice to attract the whole swarm to fly with them, has never occurred to the authors. The olfactory hypothesis needs to be rejected only in the version the authors tested, which depends on odors emitted by the scouts' Nasanov-glands. Other than that, an olfactory hypothesis which depends on odors from the cavity, that are adsorbed onto the scouts'-bodies, appears to be a very simple solution, and the only proper solution to the problem.
The case only goes to show ever new trouble that is caused by the belief that honeybees have a DL!