A beehive's storage needs directly influence the building of honeycomb. A forager bee returns to her hive with a load of nectar, transferring it to the household bee to process into honey and store. If there is no place to store the honey, the household bee must retain it within her own honey stomach. If it remains there for many hours, most of the sugar content is assimilated causing wax scales to secrete involuntarily through the wax glands on the bee's underside. This creates the necessary construction material for comb expansion. To build honeycomb in an enclosure, worker bees need an adequate food supply and a queen bee present.
The objectives of this experiment were two-fold: first, to monitor the behavior and survival of honeybees in microgravity, and secondly to compare the shape, size, volume and wall thickness of honeycombs constructed on orbit to those built by a ground control group.
Each Bee Enclosure Modules (BEM) contained approximately 3400 worker bees with a caged queen. The two BEMs were cubic flight chambers containing feeder troughs and wooden honeycomb frames. The feeder troughs within the BEM contained a mixture of water, sucrose, and agar. The agar provided a semisolid consistency to the sugar water mixture, which was necessary because in microgravity liquids bead up into free-floating droplets that are useless to the bees. The queen bees' cages were plugged with a mixture of powdered sugar and water. The worker bees consumed the plugs to release the queens.
STS-41C crewmembers observed the on-orbit BEM four times during the mission to record the bee's comb-building activities. On April 6 (9 hours after launch), survival was monitored and logged. On April 9 and 11, video recording of the bees and their behavior was performed. Final visual observations were recorded on April 13. JSC personnel monitored the ground control BEM during the mission. The ground control bees were removed from their BEM on April 12. Discovery landed on April 13 at Edwards Air Force Base, California. The BEM, with bees still inside, accompanied the flight crew to JSC the same day. The bees in the orbiter BEM were removed on April 14.
Geometric patterns were estimated using six sample pieces of the honeycomb:
The bees survived the launch. During the first video recording session on April 9, some bees attempted to fly, but collided with the chamber walls. However, by the end of the 7-day mission, the bee’s flight patterns showed complete adaptation to microgravity.
All but a few of the bees survived the week of confinement. 120 dead bees were removed from the orbiter BEM and 350 from the BEM at JSC. (Honeybees live for about six weeks on the average.)
The queen bee in the orbiter BEM laid approximately 35 eggs. These eggs failed to hatch when transferred to a standard hive near JSC. Reasons for the eggs' failure to mature are unknown and may be unrelated to the exposure to microgravity.
The bees in the orbiter BEM produced about 200 cm of honeycomb. The ground control bees at JSC built very little honeycomb during the STS-41C mission, probably because of adverse temperature conditions. Therefore, data from the 1-g trial run in September 1983 were used for comparison analysis. These bees produced more than 200 cm of honeycomb. For two of the orbiter comb pieces, cells on any one side were angled in the same direction. For the larger piece, cells on one side were angled up toward the Lexan top, while on the other side the cells were angled down toward the BEM floor. The "up-angled" cells had a higher average angle than the "down-angled." The terms "up" and "down" in microgravity are only meaningful in relation to the BEM. Another piece, which apparently started from the BEM floor, displayed a wide range of angles.
Average cell density was essentially equal for all pieces. Mean cell depths ranged from 6.4 mm to 10.8 mm. The average cell diameters were smaller and wall thickness greater for comb built in microgravity. Bees in microgravity built comb cells of normal depth and used some to store sugar syrup.
In conclusion, the bees in the orbiter BEM fared quite well in outer space, managing by mission's end to adapt perfectly to microgravity. The crew noted in the log book that "...by Day 7, comb well developed, bees seemed to adapt to 0-g pretty well. No longer trying to fly against top of box. Many actually fly from place to place." This adaptation may indicate a certain "learning" capacity on the part of the bees.
Ground control bees failed to build honeycomb most likely because they were too cold. A temperature of 33 to 36°C is necessary for comb construction and, despite the efforts of the JSC personnel to warm the BEM, temperature ranged only from 21 to 29 °C.
Prior learning could have also played a part in comb construction. The experimental bees were all about 15 days old and may have already been involved in comb construction.
Further study should be for a longer period to allow the queen's eggs to mature and use a larger flight chamber to allow more detailed observations of the bees' attempts to fly in microgravity.
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