Beyond the wing planform: morphological differentiation between migratory and nonmigratory dragonfly species.

Migration is a significant trait of the animal kingdom that can impose a strong selective pressure on several structures to overcome the amount of energy that the organism invests in this particular behaviour. Wing linear dimensions and planform have been a traditional focus in the study of flying migratory species; however, other traits could also influence aerodynamic performance. We studied the differences in several flight-related traits of migratory and nonmigratory Libellulid species in a phylogenetic context to assess their response to migratory behaviour. Wings were compared by linear measurements, shape, surface corrugations and microtrichia number. Thorax size and pilosity were also compared. Migratory species have larger and smoother wings, a larger anal lobe that is reached through an expansion of the discoidal region, and longer and denser thoracic pilosity. These differences might favour gliding as an energy-saving displacement strategy. Most of the changes were identified in the hind wings. No differences were observed for the thorax linear dimensions, wetted aspect ratio, some wing corrugations or the wing microtrichiae number. Similar changes in the hind wing are present in clades where migration evolved. Our results emphasize that adaptations to migration through flight may extend to characteristics beyond the wing planform and that some wing characteristics in libellulids converge in response to migratory habits, whereas other closely related structures remain virtually unchanged. Additionally, we concluded that despite a close functional association and similar selective pressures on a structure, significant differences in the magnitude of the response may be present in its components.

Allometry and ontogeny in Callibia diana Stål (Mantodea: Acanthopidae).

The life-cycle of Callibia diana Stål is described and linear and geometric morphometrics are used for studying allometrics and shape changes throughout this neotropical mantid species' life-cycle. Significant changes were expected in the allometry and shape of the raptorial leg and abdomen, given the importance of hunting and reproduction. The allometric slopes were obtained by using total length as the independent variable. Geometric morphometrics of landmarks were used for frontal femur and tibia. Hunting and reproduction-related structures had the steepest slopes and positive allometries. Negative growth of both disc width and head width found in the last moulting event may be a consequence of prothoracic muscle growth which is responsible for predatory strike strength. The tibial claw and femur of the raptorial leg become larger, while their spines become more orthogonal to the longitudinal axes which may facilitate prey retention. These changes in mantid shape throughout ontogeny were consistent and suggested the resource allocation and development programming of the body that improved reaching distance and prey retention.