''Bolitotherus cornutus'' is a North American species of

darkling beetle Darkling beetle is the common name for members of the beetle family Tenebrionidae. The number of species in the Tenebrionidae is estimated at more than 20,000 and the family is cosmopolitan in distribution. Taxonomy ''Tenebrio'' is the Latin gen ...

known as the horned fungus beetle or forked fungus beetle. All of its life stages are associated with the fruiting bodies of a wood-decaying shelf fungus, commonly ''

Ganoderma applanatum ''Ganoderma applanatum'' (the artist's bracket, artist's conk, artist's fungus or bear bread) is a bracket fungus with a cosmopolitan distribution. Description This fungus is parasitic and saprophytic, and grows as a mycelium within the wood o ...

'', '' Ganoderma tsugae'', and ''

Ganoderma lucidum ''Ganoderma lucidum'' is a red-colored species of ''Ganoderma'' with a limited distribution in Europe and parts of China, where it grows on decaying hardwood trees. Wild populations have been found in the United States in California and Utah, but ...

''.

Description

Adults are brown, armored beetles, long. They are

sexually dimorphic Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...

; males have two sets of horns and females lack horns. Males use their horns, clypeal and

thoracic The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the crea ...

, to compete for

mate Mate may refer to: Science * Mate, one of a pair of animals involved in: ** Mate choice, intersexual selection ** Mating * Multi-antimicrobial extrusion protein, or MATE, an efflux transporter family of proteins Person or title * Friendship ...

s. Unlike many species of

scarab beetles The family Scarabaeidae, as currently defined, consists of over 30,000 species of beetles worldwide; they are often called scarabs or scarab beetles. The classification of this family has undergone significant change in recent years. Several sub ...

that exhibit male dimorphism for horns with major and minor morphs,Emlen DJ (1996) Artificial selection on horn length body size allometry in the horned beetle ''Onthophagus acuminatus'' (Coleoptera: Scarabaeidae). Evolution 50: 1219–1230. doi:10.2307/2410662 male ''B. cornutus'' possess a continuous range of horn and body sizes.Conner JK (1988) Field measurements of natural and sexual selection in the fungus beetle, ''Bolitotherus cornutus''. Evolution 42: 736–749. doi:10.2307/2408865. Adult horned fungus beetles are active at night, but may be found during the day on the undersides of their host fungi.

Reproductive behavior

''Bolitotherus cornutus'' adults perform reproductive behaviors on the surfaces of fruiting bodies of their host fungus. Mating pairs engage in a courtship ritual in which the male grips the female's

elytra An elytron (; ; , ) is a modified, hardened forewing of beetles (Coleoptera), though a few of the true bugs (Hemiptera) such as the family Schizopteridae are extremely similar; in true bugs, the forewings are called hemelytra (sometimes alterna ...

, with his thorax over the end of her

abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. ...

. Courtship often lasts several hours, and is a necessary precursor to

copulation Sexual intercourse (or coitus or copulation) is a sexual activity typically involving the insertion and thrusting of the penis into the vagina for sexual pleasure or reproduction.Sexual intercourse most commonly means penile–vaginal penetra ...

. During a copulation attempt, the male reverses position on top of the female so that both individuals point the same direction and their abdomens are aligned. If the courtship is successful, the female opens her anal sternite and copulation takes place. Following copulation, the male remains on top, facing the same direction as the female, and mate-guards her. The male remains in this position for several hours, preventing other males from courting the female. Later, the female will deposit single eggs on the upper surface of a host fungus, then cover each egg with a distinctive dark brown oval of

frass Frass refers loosely to the more or less solid excreta of insects, and to certain other related matter. Definition and etymology ''Frass'' is an informal term and accordingly it is variously used and variously defined. It is derived from the ...

. When the eggs hatch, the larvae burrow into and consume the fungus, in which they later pupate before emerging as adults.

Parasites

Some larvae die after attack by an uncharacterized parasitic fungus, or when parasitized by a

braconid The Braconidae are a family of parasitoid wasps. After the closely related Ichneumonidae, braconids make up the second-largest family in the order Hymenoptera, with about 17,000 recognized species and many thousands more undescribed. One analysis ...

wasp, '' Eubadizon orchesiae'', that makes a light yellow silken cocoon in the body of the larva.

References

{{Taxonbar, from=Q2009476 Tenebrionidae Articles containing video clips Beetles of North America Beetles described in 1794