Abstract
Oedaleus asiaticus is one of the dominant species of grasshoppers in the rangeland on the Mongolian plateau, and a serious pest, but its migratory behavior is poorly known. We investigated the take-off behavior of migratory O. asiaticus in field cages in the inner Mongolia region of northern China. The species shows a degree of density-dependent phase polyphenism, with high-density swarming populations characterized by a brown morph, while low-density populations are more likely to comprise a green morph. We found that only 12.4% of brown morphs engaged in migratory take-off, and 2.0% of green morphs. Migratory grasshoppers took off at dusk, especially in the half hour after sunset (20:00–20:30 h). Most emigrating individuals did not have any food in their digestive tract, and the females were mated but with immature ovaries. In contrast, non-emigrating individuals rarely had empty digestive tracts, and most females were mated and sexually mature. Therefore, it seems clear that individuals prepare for migration in the afternoon by eliminating food residue from the body, and migration is largely restricted to sexually immature stages (at least in females). Furthermore, it was found that weather conditions (particularly temperature and wind speed at 15:00 h) in the afternoon had a significant effect on take-off that evening, with O. asiaticus preferring to take off in warm, dry and calm weather. The findings of this study will contribute to a reliable basis for forecasting migratory movements of this pest.
Highlights
Since the beginnings of civilization, grasshoppers, including locusts (Orthoptera: Acridoidea), have been among the most devastating agricultural pests [1,2,3,4]
We investigated the take-off behavior of migratory O. asiaticus in a field cage where we could explore the relationship between take-off and weather conditions
This result indicates that green-coloured individuals have a very weak of the 200 green morphs). This result indicates that green-coloured individuals have a very weak migration propensity, and are significantly different from the brown morph in their take-off propensity migration propensity, and are significantly different from the brown morph in their take-off (Figure 1A)
Summary
Since the beginnings of civilization, grasshoppers, including locusts (Orthoptera: Acridoidea), have been among the most devastating agricultural pests [1,2,3,4]. This group of insects contains hundreds of pest species and affects the livelihoods of one in every ten people worldwide [2]. Insects 2020, 11, 416 well known in some species, such as the desert locust (Schistocerca gregaria) [6,7] and oriental migratory locust (Locusta migratoria manilensis) [8]. Its migratory behavior has been scarcely studied and is relatively poorly known
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