Aspects of mating behavior and antennal sensilla in Anomala inconstans Burmeister, 1844 (Coleoptera: Scarabaeidae: Rutelinae)

Antennal sensilla in Cyclocephala literata Burmeister, 1847 (Coleoptera: Scarabaeidae: Dynastinae)

Abstract: Adults of the beetle Cyclocephala literata Burmeister, 1847 are important pollinators to some Magnoliaceae. Is known that insects could find host plants by detecting volatiles through antennal sensilla. Cyclocephala has its three distal antennomeres lamellate, and the surface of each lamella has sensilla trichodea, chaetica, placodea, coeloconica, basiconica and ampullacea. Three kinds of sensilla placodea were found (type I, II and III), and two kinds of sensilla coeloconica were observed (type I and II). Females have on average 10,776 sensilla, of which 10,214 are sensilla placodea, 536 are sensilla coeloconica, and 26 are sensilla basiconica. Males have on average 10,386 sensilla, of which 9,873 are sensilla placodea, 464 are sensilla coeloconica, and 49 are sensilla basiconica. Males and females have similar quantities of sensilla, and sensilla placodea are predominant. The differences observed in the number of sensilla of males and females were found in other beetles and were attributed to the detection of cospecific sexual pheromones by one of the sexes, or to the detection of plant volatiles. The antennal sensilla of C. literata is described and quantified in present study, and some perspectives about the differences kind of chemical communication, pollination, and antennae dimorphism is discussed.

Comparative morphology of antennal surface structures in pleurostict scarab beetles (Coleoptera)

The diverse pleurostict (phytophagous) scarab beetles with characteristically clubbed antennae exhibit striking morphological variation and a variety of different antennal sensilla. Here we compare the morphology of the antennal surface between major pleurostict lineages, including Cetoniinae, Dynastinae, Melolonthinae, Rutelinae, and a few outgroups, including Scarabaeinae and Hybosoridae. We identified various types of antennal sensilla morphologically and searched for phylogenetic patterns of sensilla within the Scarabaeidae. Sensilla were examined using SEM micrographs of 36 species and the occurrence of the different types of antennal sensilla was studied for each species. We observed a high diversity of sensilla, including multiple transitional forms. There were also a number of other interesting structures on the antennal surface with adaptive value, such as elongate elevations, serial bags, and fields of setae. Our results confirm earlier findings that within pleurostict scarabs there has occurred a clear differentiation of sensilla composition and patterns.

Description of mating behavior, life cycle, and antennal sensilla of Cyclocephala putrida Burmeister, 1847 (Coleoptera, Scarabaeidae, Dynastinae)

Abstract The genus Cyclocephala is common in Brazil (Coleoptera, Scarabaeidae, Dynastinae). The adults of some species are important pollinators, and the larvae develop in the soil, feed on organic matter, and contribute to nutrient cycle, but immatures of some species feed on plant roots, and some were registered causing damage in crops. The mating process of some phytophagous scarab beetles has a chemical recognition step, and the antenna is the main structure involved in the detection of odorants associated with insect communication. In the present study the mating behavior, life cycle, and antennal sensilla of C. putrida are described. The study was conducted at the Universidade Estadual de Mato Grosso do Sul, Cassilândia, Brazil. Adults were collected by a light trap installed from January 2016 to December 2017 and were taken to the laboratory for studies. Adults swarms are brief and were registered from January to February, and specimens were mostly collected at 20:00 to 22:00h. Chemical recognition may occur at least during one of the mating steps, during which the couple kept their antennae moving and the lamellae open, while females select males. In laboratory, the mating process lasted 7.5 minutes on average. The antennae of females have about 3399 sensilla and males about 4229 sensilla. Sensilla placodea types I, II, and III are the most abundant, and sensilla ampullacea, basiconica, and coeloconica are also present. The embryonic period lasted 16.0 days; first, second and third instars lasted 16.0, 48.3, and 165.3 days, respectively. The pupal period lasted 24.0 days. The period between egg deposition and adult emergency is about 271.5 days.