Imagine the brain cell density in a tiny bee being greater than the brain cell density of small birds. This fascinating fact is truly the case for many bees.
Various insect brains have independent regions separate from each other to process such information as smells, sounds, visual information, and memories. Scientists have already studied and compared the size and weight of these brains.
Some bees more than others, like the metallic green sweat bee (genus Augochlorella), have a large number of neurons for their brain sizes, or about 2 million per milligram according to scientists. This is higher than those seen by researchers in the neuron-rich cerebellums of many birds, like the goldcrest (Regulus regulus) which has 490,000 cells per milligram in comparison.
This unrelated 4:11-minute video by Seeker talks about how amazing bee brains are in general:
By comparison, ant brains have a much lower neuron density.
Rebekah Keating Godfrey from University of Arizona, along with her colleagues, used a recently developed technique to count brain cells when they were studying insect brains. They removed 450 brains from such insects as ants, bees, wasps, and a species of fly, from 32 different species.
The methodology is that the brains are ground up and soaked in a solution that frees the nucleus from each brain cell, then dye is added to make the nuclei fluoresce. Then they count the nuclei in a small sample under an ‘epifluorescence’ microscope using ultraviolet light. Based on this number, they estimate the neuron count in the animal’s brain.
Brain size does not always give a realistic understanding of brain power, whether in vertebrates like birds and mammals, or in insects. This is because flying animals like birds would be weighed down by large, heavy brains. Instead, their neurons are compacted into smaller spaces, which explains the higher cell density.
Team member Wulfila Gronenberg from University of Arizona explains that the difference in insect brain cell counts probably has little to do with intelligence. Brain tissue costs a lot of energy, so those that don’t need it don’t have it.
Ants, compared to wasps and bees, have small brains and surprisingly few brain cells. One ant species (Novomessor cockerelli) studied had only 400,000 cells per milligram.
The difference could boil down to lifestyles. Researchers think that flying insects like bees may need more neurons to power and process their enhanced complex vision and resulting visual information. They plan to test this idea in future.