Length-mass allometries of larval mosquitoes and aquatic dipterans: differences between taxa, traits and methods

Body mass underpins many ecological processes at the level of individuals,
populations and communities. Often estimated in arthropods from linear
traits such as body length or head width, these relationships can vary
even between closely related taxa. Length-mass relationships of mosquito
(Diptera: Culicidae) larvae are poorly known, despite the importance of
this taxon to disease and aquatic ecology. To fill this gap, we measured
ontogenetic changes in linear traits (body length, head width and thorax
width) and dry and wet masses, and estimated length- and width-mass
relationships in larvae of three Culicidae species inhabiting different
niches: the tropical Aedes albopictus (Skuse, 1894), the temperate Culex
pipiens (Linnaeus, 1758) and the snowmelt Ochlerotatus punctor (Kirby,
1837). We compared these data with published length-weight allometries of
other larval aquatic dipterans. We show that thorax width and body length,
but not head width, reliably predict body mass for the three mosquito
species. The length-mass allometry slopes in aquatic dipterans vary
considerably between and within families but are independent of phylogeny,
specimen handling, preservation techniques, and data fitting method.
However, slope estimates become less precise with decreasing sample size
and size range. To obtain reliable estimates of the allometric slopes, we
recommend using data on all larval stages for intraspecific allometries
and a wide range of species for interspecific allometries. We also caution
against indiscriminately using of length-mass allometries obtained for
other taxa or collected at lower taxonomic resolution, e.g. when using
length-mass relationships to estimate biomass production at a given
site.