Abstract
Flight loss has occurred in many winged insect taxa. The flightless silkmoth Bombyx mori, is domesticated from the wild silkmoth, Bombyx mandarina, which can fly. In this paper, we studied morphological characteristics attributed to flightlessness in silkmoths. Three domestic flightless B. mori strains and one B. mandarina population were used to compare morphological components of the flight apparatus, including wing characteristics (shape, forewing area, loading, and stiffness), flight muscle (weight, ratio, and microscopic detail) and body mass. Compared with B. mandarina, B. mori strains have a larger body, greater wing loading, more flexible wings and a lower flight muscle ratio. The arrangement in microscopy of dorsal longitudinal flight muscles (DLFMs) of B. mori was irregular. Comparative analysis of the sexes suggests that degeneration of flight muscles and reduction of wing mechanical properties (stiffness) are associated with silkmoth flightlessness. The findings provide important clues for further research of the molecular mechanisms of B. mori flight loss.
Highlights
Insects occur worldwide and their distributions have been shaped by their ability to fly
To validate whether a morphology affects the flight of silkmoth, we mainly considered the three pairs comparisons between flying B. mandarina and each of the three flightless B. mori
B. mandarina were significantly different with each of the three B. mori populations (Table 3; Figure 2)
Summary
Insects occur worldwide and their distributions have been shaped by their ability to fly. Insect flight may have evolved more than 400 million years ago [1]. Many winged insects have secondarily become flightless during their evolution [2,3]. In 1854, Wollaston documented that 200 of 550 beetles in the Madeiran archipelago had lost their ability to fly [4,5]. Some orders, such as Grylloblattodea and Siphonaptera, are entirely flightless [6]. In Lepidoptera species, the flight ability of migratory and non-migratory populations of the monarch butterfly is different [7]
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