Data accompanying manuscript: Allometric analysis of brain cell number in Hymenoptera suggests ant brains diverge from general trends

Many comparative neurobiological studies seek to connect sensory or
behavioral attributes across taxa with differences in their brain
composition. Such studies can only be interpreted in a meaningful way if
the general brain-body relationships are known on a larger taxonomic
scale. Recent studies in vertebrates suggest cell number and density may
be better correlated with behavioral ability than brain mass or volume,
but few estimates of such figures exist for insects. Here we use the
isotropic fractionator method to estimate total brain cell numbers for 29
genera of Hymenoptera spanning seven subfamilies. We find estimates from
using this method are comparable to traditional, whole-brain cell counts
of two species and to published estimates from established stereological
methods.  We present allometric scaling relationships
between body and brain mass, brain mass and nuclei number, and body mass
and cell density and find that ants stand out from bees and wasps as
having particularly small brains by measures of mass and cell number. We
find that Hymenoptera follow the general trend of smaller animals having
proportionally larger brains. Smaller Hymenoptera also feature higher
brain cell densities than the larger ones, as is the case in most
vertebrates, but in contrast with primates, in which neuron density
remains rather constant across changes in brain mass. Overall, our
findings establish the isotropic fractionator as a useful method for
comparative studies of brain size evolution in insects.