Precopulatory behavior and sexual conflict in the desert locust

Abstract

Studies of mating and reproductive behavior have contributed much to our understanding of various animals’ ecological success. The desert locust, Schistocerca gregaria, is an important agricultural pest. However, knowledge of locust courtship and precopulatory behavior is surprisingly limited. Here we provide a comprehensive study of the precopulatory behavior of both sexes of the desert locust in the gregarious phase, with particular emphasis on the conflict between the sexes. Detailed HD-video monitoring of courtship and mating of 20 locust pairs, in a controlled environment, enabled both qualitative and quantitative descriptions of the behavior. A comprehensive list of behavioral elements was used to generate an eight-step ethogram, depicting from first encounter between the sexes to actual copulation. Further analyses included the probability of each element occurring, and a kinematic diagram based on a transitional matrix. Eleven novel behavioral elements are described in this study, and two potential points of conflict between the sexes are identified. Locust sexual interaction was characterized by the dominance of the males during the pre-mounting stage, and an overall stereotypic male courtship behavior. In contrast, females displayed no clear courtship-related behavior and an overall less organized behavioral sequence. Central elements in the sexual behavior of the females were low-amplitude hind-leg vibration, as well as rejecting males by jumping and kicking. Intricate reciprocal interactions between the sexes were evident mostly at the mounting stage. The reported findings contribute important insights to our knowledge of locust mating and reproductive behavior, and may assist in confronting this devastating agricultural pest.

Sexual behavior of the desert locust during intra-and inter-phase interactions

“…Experiments were carried out as described by Golov et al (2018). Briefly, a male and a 143 female locust, in the solitary phase, were introduced into the two sides of an observation 144 cell (14x13x24 cm, divided in two by an opaque plastic partition).…”

“…The above-noted study by Golov et al (2018), however, as well as most of the above-72 mentioned earlier work, was limited to locusts in the gregarious phase (but see 73 Inayatullah et al, 1994). In the gregarious phase, the desert locust displays clear sexual 74 dimorphism, in which fully mature males are bright yellow and females beige-brown to 75 yellowish (Norris, 1954;Pener, 1965;Pener & Simpson, 2009).…”

“…Locust courtship, in general, is considered simple and primitive (Loher, 1959;60 Uvarov, 196660 Uvarov, , 1977Strong & Amerasinghe, 1977). Males of S. gregaria were reported 61 to be more dominant during sexual-interactions, while females were reported to show 62 no clear courtship behavioral patterns (Norris, 1954;Pener, 1965Pener, , 1967Strong & 63 Amerasinghe, 1977;Amerasinghe, 1978;Inayatullah et al, 1994;Golov et al, 2018). A 64 major feature of the female locust sexual behavior was reported to be rejection of the 65 males: including jumping (before and during mounting), kicking, and movements of the 66 abdomen to prevent copulation (Loher, 1959;Strong & Amerasinghe, 1977;Uvarov, 67 1977;Golov et al, 2018).…”

“…Males of S. gregaria were reported 61 to be more dominant during sexual-interactions, while females were reported to show 62 no clear courtship behavioral patterns (Norris, 1954;Pener, 1965Pener, , 1967Strong & 63 Amerasinghe, 1977;Amerasinghe, 1978;Inayatullah et al, 1994;Golov et al, 2018). A 64 major feature of the female locust sexual behavior was reported to be rejection of the 65 males: including jumping (before and during mounting), kicking, and movements of the 66 abdomen to prevent copulation (Loher, 1959;Strong & Amerasinghe, 1977;Uvarov, 67 1977;Golov et al, 2018). We recently provided a first comprehensive description of the 68 pre-copulatory behavior of the gregarious desert locust (Golov et al, 2018), presenting a 69 detailed quantification of the sexual behavior of both sexes, with special emphasis on 70 female choice.…”

“…A 64 major feature of the female locust sexual behavior was reported to be rejection of the 65 males: including jumping (before and during mounting), kicking, and movements of the 66 abdomen to prevent copulation (Loher, 1959;Strong & Amerasinghe, 1977;Uvarov, 67 1977;Golov et al, 2018). We recently provided a first comprehensive description of the 68 pre-copulatory behavior of the gregarious desert locust (Golov et al, 2018), presenting a 69 detailed quantification of the sexual behavior of both sexes, with special emphasis on 70 female choice. 71…”