Female bias in an immigratory population of Cnaphalocrocis medinalis moths based on field surveys and laboratory tests

Abstract

Sex ratio bias is common in migratory animals and can affect population structure and reproductive strategies, thereby altering population development. However, little is known about the underlying mechanisms that lead to sex ratio bias in migratory insect populations. In this study, we used Cnaphalocrocis medinalis, a typical migratory pest of rice, to explore this phenomenon. A total of 1,170 moths were collected from searchlight traps during immigration periods in 2015–2018. Females were much more abundant than males each year (total females: total males = 722:448). Sex-based differences in emergence time, take-off behaviour, flight capability and energy reserves were evaluated in a laboratory population. Females emerged 0.78 days earlier than males. In addition, the emigratory propensity and flight capability of female moths were greater than those of male moths, and female moths had more energy reserves than did male moths. These results indicate that female moths migrate earlier and can fly farther than male moths, resulting more female moths in the studied immigratory population.

The Population Growth of Spodoptera frugiperda on Six Cash Crop Species and Implications for Its Occurrence and Damage Potential in China

“…Females that emerge early are more likely to disperse because they need to find food and locate suitable oviposition sites. Similar to our results, earlier female emergence has been reported in migratory insects such as Pseudaletia unipuncta (Haworth) (Lepidoptera: Noctuidae) [ 33 ], Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) [ 34 ] and Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Pyralidae) [ 35 ]. Furthermore, migratory female insects possess a greater migration capacity than males, which ensures the rapid expansion of migratory populations.…”

Insect Target Classes Discerned from Entomological Radar Data

“…Useful RCS and CLPP information may also be obtainable via electromagnetic modelling [42], though with reduced strength of inference if used for target identification. Knowledge of the temperature-range for sustained flight for each species of interest will also have interpretive value and may be obtained through careful laboratory measurement [43] or inferred from field observations.…”

Adaptive strategies of Rice Leaf Roller, Cnaphalocrocis medinalis in Response to Different Rearing Temperatures

“…Interestingly, female moths have stronger flight propensity than males in some species [64], which undertake the task of finding food and oviposition sites [65]. Guo et al [36] reported that female C. medinalis had a greater migratory propensity and flight capability than males at constant 26 °C in a laboratory population. Similar patterns were observed in M. separata [66] and Culex pipiens pallens [67].…”

“…The lower value of the period of eclosion represented the synchronized eclosion. The sex ratio was used to calculate the proportion of female and male adults [36].…”

“…A short hollow-plastic tether was glued to the dorsal surface of the metathorax using 502 super adhesives (Beijing Chemical Co.) and the adults were provided with 10% honey solution (v/v) before tethered flight. All tethered moths were tested for 6-h flight (23:00-05:00) on flight mills under dark condition at 26 ±1°C and 80%-85% RH [24,35,36]. The number of replicates of five immature temperature treatments (18, 22, 26, 30 and 34°C) were 14, 28, 19, 14 and 26 females, and 14, 30, 28, 15, 30 males, respectively.…”