Hair-pencils and coremata are

pheromone A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...

signaling structures present in

lepidoptera Lepidoptera ( ) is an order (biology), order of insects that includes butterfly, butterflies and moths (both are called lepidopterans). About 180,000 species of the Lepidoptera are described, in 126 Family (biology), families and 46 Taxonomic r ...

n males. Males use hair-pencils in

courtship Courtship is the period wherein some couples get to know each other prior to a possible marriage. Courtship traditionally may begin after a betrothal and may conclude with the celebration of marriage. A courtship may be an informal and private m ...

behaviors with females. The pheromones they excrete serve as both

aphrodisiacs An aphrodisiac is a substance that increases sexual desire, sexual attraction, sexual pleasure, or sexual behavior. Substances range from a variety of plants, spices, foods, and synthetic chemicals. Natural aphrodisiacs like cannabis or cocain ...

and

tranquilizers A tranquilizer is a drug that is designed for the treatment of anxiety, fear, tension, agitation, and disturbances of the mind, specifically to reduce states of anxiety and tension. Etymology Tranquilizer, as a term, was first used by F.F. Yonkm ...

to females as well as repellents to

conspecific Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species. Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organ ...

males.Hillier, N., & Vickers, N. (2004). The Role of Heliothine Hair-pencil Compounds in Female Heliothis virescens (Lepidoptera: Noctuidae) Behavior and Mate Acceptance. ''Chemical Senses'', 6 (29), 499-511. Hair-pencil

glands In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormones) for release into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland). Structure De ...

are stored inside the male until courtship begins, at which point they are forced out of the body by sclerotized levers present on the abdomen.Birch, M. C., & Poppy, G. M. (1990). Scents and Eversible Scent Structures of Male Moths. ''Annual review of Entomology'' (35), 25-58. Coremata (the singular form being corema) are very similar structures. Their exact definition is confused by early descriptions but they are more specifically defined as the internal, glandular, eversible structures that bear the hair-pencils and can be voluntarily inflated with

hemolymph Hemolymph, or haemolymph, is a fluid, analogous to the blood in vertebrates, that circulates in the interior of the arthropod (invertebrate) body, remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which ...

or air.Bobera, R., & Rafaeli, A. (2010). Gene-silencing reveals the functional significance of pheromone biosynthesis activating neuropeptide receptor (PBAN-R) in a male moth. ''Proceedings of the National Academy of Sciences'', 107 (39), 16858-16862.

Behavioral use of hair-pencils

Male moths are attracted from relatively long distances by females releasing pheromones; when they are close enough to the females to begin courtship, the hair-pencils are extruded from the abdominal cavity and pheromones are fanned towards the female.Davie, L. C., Jones, T. M., & Elgar, M. A. (2010). The role of chemical communication in sexual selection: hair-pencil displays in the diamondback moth, Plutella xylostella. ''Animal Behaviour'' (79), 391-399. Fanning can occur in various ways including extruding and retracting the hair-pencils, wing or abdominal movement, or flight in front of the female. When the female moth becomes receptive to the male hair-penciling, she will flick her antennas rapidly in response to his pheromone cues.Lassance, J.-M., & Löfstedt, C. (2009). Concerted evolution of male and female display traits in the European corn borer, Ostrinia nubilalis. ''BioMed Central Biology'', 7 (10), 1-12. If the female likes the male blend of pheromones, then she will extend her abdomen and

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 penetrat ...

begins.

Hair-pencil pheromone effects

It has been shown that the hair-pencil pheromones serve both as an aphrodisiac or tranquilizer for the female, but sometimes as a repellent to other conspecific males. In an experiment with heliothine moths, male hair-pencil compounds were extracted and tested against various male and female treatments. It was found that not one specific compound triggered a response in females, but a blend was required. Additionally it is thought that the specific ratio of each of the compounds found in the male moths helps females determine a suitable male from her species. Heliothine moths use similar hair-pencil compounds in different ratios and this is enough for the female to differentiate conspecifics from other species. Males are able to detect competitors through hair-pencil compounds, but extra competitors do not cause great increases in display rate. This perhaps is due to the suppressing effect of hair-pencil pheromones on competitors. Pheromones have also been demonstrated to show the age of the male. As males age the pheromone chemical ratios change slightly. Females can distinguish between males by these changes and pick a more suitable mate.

Plants and insect relations

Some of the pheromone compounds that are produced in the hair-pencils of the insects have been found to come from plants . In particular,

pyrrolizidine alkaloids Pyrrolizidine alkaloids (PAs), sometimes referred to as necine bases, are a group of naturally occurring alkaloids based on the structure of pyrrolizidine. Pyrrolizidine alkaloids are produced by plants as a defense mechanism against insect he ...

have been found to play a role in male pheromones. These compounds can be formed by

de novo synthesis In chemistry, ''de novo'' synthesis () refers to the synthesis of complex molecules from simple molecules such as sugars or amino acids, as opposed to recycling after partial degradation. For example, nucleotides are not needed in the diet as the ...

or by modifying a pre-existing pyrrolizidine alkaloid that is consumed from the plant. These base compounds can be either eaten in the larval stage or imbibed in the adult stage. They are so important that stepping on a substance containing these compounds causes immediate

proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elong ...

extension in adults.Honda, Y., Hond, K., & Ômura, H. (2006). Major components in the hair-pencil secretion of a butterfly, Euploea mulciber (Lepidoptera, Danaidae): Their origins and male behavioral responses to pyrrolizidine alkaloids. ''Journal of Insect Physiology'' (52), 1043-1053. Studies have also been done testing the effects of growth of the hair-pencil organs related to the ingestion of plant pyrrolizidine alkaloids. It was found that without the plant derived compounds the hair-pencil organs are smaller. The alkaloid compounds are transformed after ingestion in the

. The stimulatory effects of the alkaloid derived compounds begin in the larval stages and are displayed in adult stages.Jordan, A. T., Jones, T. H., & Conner, W. E. (2007). Morphogenetic Effects of Alkaloidal Metabolites on the Development of the Coremata in the Salt Marsh Moth, Estigmene acrea (Dru.) (Lepidoptera: Arctiidae). ''Archives of Insect Biochemistry and Physiology'' (66), 183-189.

References

{{DEFAULTSORT:Hair-Pencil Lepidopterology Insect anatomy