Harlequin beetle

Taxonomy

The harlequin beetle was first scientifically described as Cerambyx longimanus by Linnaeus in the 10th edition of Systema Naturae in 1758. In 1806, it was moved to the newly coined genus Acrocinus by Illiger. Although recent authorities have consistently recognized it as the only member of this genus, the relationship to other genera of longhorned beetles has not been clear: It has been disputed whether the tribe Acrocinini only should include the genus Acrocinus or it also include a few other genera. Recent authorities have often considered Acrocinini as monotypic, but an analysis of morphological characters indicates that Macropophora and Oreodera are sufficiently close to also be included in this tribe.

Despite the very large distribution of the harlequin beetle, both morphological and genetic evidence supports its status as a single widespread species rather than a cryptic species complex.

Distribution and habitat

The harlequin beetle is found in tropical and subtropical parts of the Americas, ranging from Mexico, through Central and South America, south as far as northernmost Argentina (Corrientes and Misiones), southernmost Brazil (Rio Grande do Sul) and Paraguay. It also occurs on the Caribbean island nation of Trinidad and Tobago, The harlequin beetle has been recorded from all Central American countries and all South American countries, except Chile and Uruguay. In Mexico, its distribution is incompletely known, but it is found in the south of the country, ranging north along the western side of the central plateau to Sinaloa and along the eastern side to San Luis Potosí.

The harlequin beetle is locally common and while most records are from undisturbed forests, it also occurs in secondary forest and occasionally even in cities if there are green areas nearby. Most of its South American range is in the Amazon and Atlantic forests, but it also occurs more locally in the Cerrado and Caatinga, It has been recorded at elevations up to 2150 m above sea level.

Sexual dimorphism and behavior

Male and female harlequin beetles have similar color patterns and reach a similar body size, but the species is sexually dimorphic in the foreleg length and shape: In large males, the forelegs are greatly extended, up to 15 cm long, being twice the length as in females with the same body size. Large males also exhibit strong curvature in their foreleg tibiae, which is not seen in females. However, in small males, both length and shape of the forelegs resemble that seen in small females. These traits aid the males as they fight with each other over optimal egg deposition sites in preparation for mating. Males engage each other with their forelimbs in an attempt to flip other males off of the dead or dying trees that may be chosen by females to provide food for developing larvae. The males also readily attempt to bite each other with their strong mandibles, sometimes biting off pieces of the opponents antennae or legs. Once a site has been secured, the male will guard it around the clock, but females typically only are present during nighttime; once a female arrives, the male will also guard her.

Harlequin beetles mainly fly during the night and appear to be able to rapidly locate recently fallen trees through the smell of the large amounts of sap that is released when it happens. but otherwise harlequin beetles play an important role in the early phase of decomposition of dead wood, also creating habitats for other saproxylic species.

The adult beetles can live up to about half a year, and they will feed on sap, wood, fungi and occasionally animal droppings. There is a level of seasonality in the species; adult beetles can be seen year-round, but they are most abundant in the first few months of the rainy season.

Relationship with pseudoscorpions

Tiny pseudoscorpions may attach themselves or hide under the wing coverts of harlequin beetles to use them for transport, which is a form of phoresy. In one case, fifteen pseudoscorpion had hidden themselves under the wing coverts of a harlequin beetle, but their combined weight was still less than 2.5% of the beetle's. Once transported to a recently fallen tree by harlequin beetles, a new pseudoscorpion colony is formed and remains isolated until the next generation of harlequin beetles have completed their immature stages (egg, larvae and pupae) in the wood and emerge as adult beetles. At that point, pseudoscorpions from the colony will attach themselves to the emerging beetles to be transported to a new recently fallen tree, starting the cycle over again.

Anti-fungal properties

The harlequin beetle contains three homologous peptides, Alo-1, Alo-2, and Alo-3. Alo-3 was the first known peptide from insects to exhibit the knottin fold. It has a higher level of activity against the fungal species Candida glabrata than the Alo-1 and Alo-2 peptides do. Currently, there is a lack of treatment for fatal hospital-acquired infections and other pathologies. The peptide Alo-3 found in Harlequin beetles could provide a treatment for these severe, life threatening infections.

References

References

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