Measuring Intraspecific Variation in Flight-Related Morphology of Monarch Butterflies (Danaus plexippus): Which Sex Has the Best Flying Gear?

Abstract

Optimal flight in butterflies depends on structural features of the wings and body, including wing size, flight muscle size, and wing loading. Arguably, there is no butterfly for which flight is more important than the monarch (Danaus plexippus), which undergoes long-distance migrations in North America. We examined morphological features of monarchs that would explain the apparent higher migratory success and flight ability of females over males. We examined 47 male and 45 female monarch specimens from a project where monarchs were reared under uniform conditions. We weighed individual body parts, including the thorax (flight muscle) and wings, and computed wing loading and wing thickness for all specimens. When we compared each morphological trait between sexes, we found that females did not differ from males in terms of relative thorax (wing muscle) size. Females were generally smaller than males, but females had relatively thicker wings than males for their size, which suggests greater mechanical strength. Importantly, females had significantly lower wing loading than males (7% lower). This would translate to more efficient flight, which may explain their higher migratory success. Results of this work should be useful for interpreting flight behavior and/or migration success in this and other Lepidopteran species.

Identification of genes underlying phenotypic plasticity of wing size via insulin signaling pathway by network-based analysis in Sogatella furcifera

“…Of note, genes encoding the structural components of flight muscles, such as flightin , troponin C, twitchin and unc89 , has abundant accumulations in MFW, and are markedly higher than those in BFW. These flight muscle genes are involved in the construction of essential mechanical flight apparatus and their relative abundance in the MFW correlates with a strong flight capability [68–70]. Our findings on the increasing expression of flight muscle genes in the macropterous morph corroborates those of Xue et al [26], Brisson et al [71] and Yang et al [27] who asserted that flight muscle genes are highly abundant in the flight capable wing forms of N. lugens and aphids compared with the flightless ones.…”

Host suitability and feeding preference of the African citrus triozid Trioza erytreae Del Guercio (Hemiptera: Triozidae), natural vector of “Candidatus Liberibacter africanus”

“…Plant quality affects the morphological and physiological variability in T. erytreae (Moran, ), and the nutritional quality of the different host plants could be responsible for the observed variation in the size of the emerged adults. Lower wing loading in female Monarch butterflies Danaus plexippus (L.) (Lepidoptera: Nymphalidae) was associated with efficient flight and migratory success (Davis & Holden, ). Tibia length was significantly longest in adult ACTs reared on M. koenigii , underlining the good host plant quality of this species as also noted in most of the studied biological parameters.…”

Larval pesticide exposure impacts monarch butterfly performance

“…After a butterfly died, date of death was recorded and its size was measured by folding the wings together and measuring from the farthest tip of the forewing to the first white dot on the thorax 56 . There is a linear relationship between forewing length and size in monarchs 57 and butterflies in general 58 .…”