1) Researchers trapped and photographed paper wasps across an elevational gradient in the Colombian Andes to examine how their body color varied with elevation. 2) They found that wasps from higher elevations had significantly darker thoraxes, supporting the prediction that ectotherms are darker at higher elevations to aid heat absorption and provide photoprotection from UV radiation. 3) In contrast, the coloration of other body parts like the head and abdomen did not consistently vary with elevation, except the clypeus which became more matte at higher elevations, suggesting darker thoraxes specifically aid thermoregulation in wasps living in colder, high-elevation environments.

1. Paper wasps are darker at high elevation
André R. de Souza (Universidade de São Paulo, Brazil)
Angie Z. Mayorquin (Universidad Nacional de Colombia, Colombia)
Carlos E. Sarmiento (Universidad Nacional de Colombia, Colombia)
Contact: andrebioufjf@gmail.com
Full article at: Journal of Thermal Biology 89:102535 (2020)

2. Introduction
• High mountains are harsh environments due to low temperatures and high levels of UV-B
radiation. Adaptations to live in such habitats are common.
• Elevational gradients provide a good system to test the adaptiveness of intraspecific variation in
species that occur from low to high elevations.
• Tegument melanization improves heat gain and provides photoprotection. Thus, at high elevation,
ectotherms are expected to be darker (well-melanized).
• We test this prediction in the paper wasp Agelaia pallipes (Hymenoptera: Vespidae), an insect
species distributed across an elevational gradient in the Colombian Andes.

3. Materials & Methods
• Each expedition: four Malaise traps filled with 95%
etanol, spaced by 100 m, set out for 10 days in a
collection site with known elevation. More details in
Tab 1.
• Sample: A total of 146 wasps (11-20 females per
elevation).
• Standard digital photography to measure the body
luminance and colour patterning in different body
parts of dry-preserved specimens. More details in Fig
1.
Fig. 2- Sketch of wasp
body indicating parts in
which colour variation was
examined.
Field expeditions to trap wasps from diferent elevations,
then examine body color with standard digital
photography
Tab.1- Details of field expeditions to collect A. pallipes paper
wasps in different elevations.

4. Results
Striking variation in body coloration (Fig.2)
Wasps from higher elevations had darker
thoraces, confirming our prediction (Fig. 3)
Fig. 2- Examples of body
colour variation in A. pallipes
paper wasps from different
elevations. Pictures illustrate
some variation in the female
clypeus (although
consistently black, it ranges
from shiny to matte as the
elevation increases,
comprising differences in
surface texture),
mesoescutum (note the
patched coloration and the
variation in the number, size,
and luminance of the
yellowish stripes, so that
they are all reduced as the
elevation increases), tergite
and sternite (note the
variation of brownish and
yellowish smoothed
patterns, those are not
associated to elevation).
Fig. 3- Body colour variation in
A. pallipes in relation to the
elevation of collection. Each
black dot refers to a single
individual and the lines
represent a significant
association according to
regression analyses (p<0.05).

5. Discussion
Coloration of A. pallipes paper wasp varies with
elevation. Thorax dorsal coloration is darker in
higher elevation, presumably to improve heating of
muscles associated with flight. By contrast,
coloration of other parts such as head and abdomen
did not vary with elevation, except for clypeus which
becomes more matte with elevation. These findings
suggest that wasps are darker at high elevations in
order to improve their thermoregulation and protect
them from UV-B radiation.