Scarab beetles use pheromones and volatiles to search for their partners and host plants. The perception of these compounds occurs in the beetle antennae, particularly in the sensilla. Relatively few studies have morphologically and physiologically characterized the sensilla of scarab beetles. Cyclocephala barrerai Martínez is a beetle distributed in Mexico. Male beetles have larger antennal lamellae than females, and in both cases, the size of this structure is related to their weight. Previous studies have reported that both sexes are attracted to bacterial volatiles isolated from the female genital chambers. Female cuticular hydrocarbons may act as a sexual contact pheromone. However, antennal sensilla and their electrophysiological responses to behaviorally relevant compounds remain to be investigated. Here, we describe and report the types, allometric relationships, and functions of sensilla found in the lamellae of both C. barrerai sexes. Sensilla were identified, classified, measured, and counted to identify intra and intersexual relationships. The single sensillum recordings showed that plant volatiles, hydrocarbons, and heat stimulated receptor neurons. We identified 2 new types of sensilla basiconica in the scape. Males have more and larger antennal sensilla placodea IV, which specializes in detecting pheromones, plant volatiles, and heat. Females have a greater diversity of sensilla.

Sexual selection determines the evolution of the species by favoring some attributes that confer a reproductive advantage to those individuals with those attributes. Tephritidae flies do not always select the same traits when looking for a mating partner. Some aspects of the mating system of Anastrepha curvicauda are known; nevertheless, there is no information on the effect of age, size, and virginity when selecting a mating partner. We set up a series of experiments where a selector (male or female) may select between (a) an old or young partner, (b) a small or large partner, and (c) a virgin or mated partner. Males of A. curvicauda significantly preferred large, young, and virgin females, while females showed no preference for high- or low-quality males. The females’ non-preference for a particular male is discussed in the light of their mating system.

Our study aimed to characterize mating behavior in virgin and once-mated males and females of Cyclocephala barrerai. We reared the specimens under laboratory conditions and recorded the age at which the organisms began their reproductive activity and the time they remained active. We characterized behavioral acts during mating in two groups—virgin and once-mated organisms. Transitions between behaviors were analyzed using Markov chains and the generated ethograms. The duration of behaviors and the percentage of transitions were compared between the two groups. To characterize the mating behavior of C. barrerai, we adopted a framework commonly used in the literature, dividing mating behavior into three phases: premating, mating, and postmating. (A) Premating: Males search for females and mount and stimulate them, which the females resist through fighting behaviors. (B) Mating: The male mounts the female, which moves around and then stops; the male performs specific movements of the antennae and head and inserts his aedeagus into the female. (C) Postmating: Males exhibit guarding behavior over females. Although differences in pre- and postmating behaviors were observed between virgin and once-mated organisms, the duration of the acts did not show significant differences. These results provide key information on the reproductive behavior of C. barrerai, contributing to a better understanding of their biology and sexual interaction patterns.

A major challenge in studying the biology of the Melolonthidae has been the lack of a consistent supply of organisms with known characteristics. This study aimed to develop a methodology for mass-rearing a Cyclocephala barrerai Martínez (Coleoptera: Melolonthidae) colony over several laboratory generations. The mass-rearing was initiated with eggs from wild-collected adults; each developmental instar was reared under conditions suited to their environmental and nutritional needs. Insect survival, egg-adult cycle length, sex ratio, adult weight, and number of eggs laid by each female were recorded for each generation. The morphology of mass-rearing organisms was compared to that of the wild-collected specimens. A second cohort of organisms from the original generation was reared under identical conditions and their survival, duration, and morphometry of each larval instar were recorded weekly. These data were then compared to those from the original group to assess the impact of constant manipulation during the larval instar. The mass-rearing methodology proposed in this work successfully reared 3 generations of C. barrerai with an overall average egg-adult survival rate of 66.6%. The egg-adult cycle length, proportion of females and males, and average weight differed among generations. The F1 organisms presented similar morphometrics to those collected in the field. Manipulation significantly reduced insect survival. Mass-rearing of C. barrerai facilitates a comprehensive study of its biology and may establish the species as a model for the Melolonthidae. This methodology establishes the foundations for rearing congeneric species in the laboratory.