Would Honeybees Choose Smaller or Larger Entrances?

Beehive Entrances are as varied as beekeepers who tend them, and there’s a lot of opinions on how large or small a beehive’s entrance ought to be. While it’s not uncommon for beekeepers to reducers their openings during colder periods, large entrances are common during honey flows.

But has anyone stopped to ask the bees? As it turns out, someone has. That someone, is Dr. Thomas Seeley, a world-renowned bee researcher working out of Cornel University. Seeley asked the bees by releasing swarms on a barren island and offering them the choice between different nest boxes. Their differences; entrances of 15, 30, and 60 cm². Dr. Seeley wrote about his finding, and many others, in his fantastic book, Honeybee Democracy. Here’s an excerpt:

If we gave a swarm of bees a 40-litre nest box with a 15 cm² entrance, they showed great interest in the box…There could be no doubt that the scout bees judged this box to be highly desirable… But after we enlarged the entrance opening to 60 cm²… the number of bees outside the box plummeted… This sudden abandonment of the box suggested that the scout were no longer attracted to it. … These results, confirmed by those obtained from a secoond swarm a few days later, taught us that scout bees judge a nest box with a 30 or 60 cm² entrance opening to be a low-quality, probably even unacceptable, homesite.

– Thomas D Seeley, Honeybee Democracy, Page 107

Beehive Entrance Dimensions

Thus, given a choice and everything else being equal, Dr. Seeley’s research concluded that bees have a strong preference towards small hive entrances. Interestingly, Seedey found no strong preference for the entrance shape.

Modern hives tend to have a short wide entrance that runs the width of the bottom board. This entrance can be made smaller with the addition of an entrance reducer. Fixing the hight of a hive’s entrance at 3/8″ (bee space) and translating Dr. Seeley’s research into rectangular hive openings of 15, 30, and 60cm² we get:

• 15cm² Beehive Entrance = 2.33 inches² = (3/8″ bee space) high x 6.2″ wide
• 30cm² Beehive Entrance = 4.65 inches² = (3/8″ bee space) high x 12.4″ wide
• 60cm² Beehive Entrance = 9.30 inches² = (3/8″ bee space) high x 24.8″ wide

For comparison, the opening of a commercial langstroth hive without an entrance reducer can be as large as 11 square inches. That’s more than four and a half times larger than the entrance preferred by bees!! Why are we keeping bees in hives whose entrances are of “low-quality, probably even unacceptable”?

Why Do Honeybees Prefer Smaller Beehive Entrances?

While this study doesn’t answer all of the questions – do bee prefer entrances of 10 cm² over 15 cm²? At what point does a colony judge an opening to be too small? – it does strongly suggests that bees prefer small entrances over large ones. This preference could be because smaller entrances are more easily defended. Beekeepers know that adding reducers deters robbing. It could also be that smaller openings prevent bees from drifting between nearby colonies. Less drift could mean less disease transfer. Then again, wild colonies tend widely spaced.

Another reason for this preference could be that small entrances make it easier for bees to regulate the internal temperature and humidity of the colony. My hunch is that it’s less work to cool than heat the hive. Colder temperatures cause the bees to cluster around the brood and heat it with their bodies. I hypothesize that hives with smaller entrances might be more active as fewer resources and time would be required to maintain the correct internal temperature and humidity.

Beecentric Beehive Entrances

The Beecentric Hive comes with two entrances and two entrance reducers. Built into the screened IPM bottom board, the bottom entrance has a reducer with an opening of 13 cm² (exact dimensions 3/8″ by 5.5″), which is in alignment with the preference of honeybees. Removing the reducer reveals a 30 cm² opening, but I leave the reducer on year-round; summer and winter. The bees have no problems defending a 13 cm³ entrance, and it’s large enough to accommodate heavy honey flows.

The hive has an upper entrance built into the Warre style top-quilt and a reducer with a 1.8 cm² opening. While bees can use this as an entrance, its primary functions as ventilation. Since the Beecentric Hive has a screened top-quilt, I generally keep my top-entrance closed by tipping the reducer ninety-degrees. I sometimes open it in early spring when bees are making cleaning flights. This top-entrance is probably unnecessary, but easy to close-up and offers more options.