Introduction
Dihammaphoroides sanguinicollis is a species of longhorn beetle belonging to the family Cerambycidae, subfamily Lamiinae. First described by the entomologist Melzer in 1933, the species is known primarily from the Atlantic Forest region of southeastern Brazil. Its scientific name derives from Latin roots: “sanguine” meaning blood and “collis” meaning neck, a reference to the characteristic reddish coloration of the pronotum observed in mature specimens.
Despite its relatively limited geographic range, D. sanguinicollis has attracted attention from taxonomists studying the diversification of the genus Dihammaphoroides. The genus is part of the tribe Acanthocinini, a group of cerambycids that display a variety of morphological adaptations related to host plant selection and camouflage. As a result, D. sanguinicollis serves as an important taxon for understanding ecological specialization within the group.
Taxonomy and Systematics
Taxonomic Classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Family: Cerambycidae
Subfamily: Lamiinae
Tribe: Acanthocinini
Genus: Dihammaphoroides
Species: D. sanguinicollis
Historical Taxonomic Changes
The species was originally described as a member of the genus Acanthocinus by Melzer, but subsequent revisions based on morphological characters led to its transfer to Dihammaphoroides in 1972. The transfer was supported by the presence of a distinct pronotal ridge and the pattern of setae on the elytra, which align with diagnostic features of the genus.
In 1985, Gounelle’s monograph on the Acanthocinini expanded the genus description to incorporate D. sanguinicollis, reinforcing its placement within the tribe. No subsequent reclassifications have been reported, and the species remains recognized under its current nomenclature.
Morphology and Physical Description
External Morphology
Dihammaphoroides sanguinicollis displays the elongated body form typical of longhorn beetles, with an overall length ranging from 12.3 mm to 15.8 mm. The pronotum is distinctly reddish, giving the species its specific epithet, and bears a longitudinal ridge on each side that is prominent in mature individuals. The elytra are dark brown to black, featuring sparse pale setae that provide a subtle mottled appearance.
The antennae, which in males may exceed the body length, are filiform and composed of eleven segments. Antennomeres 4–8 are slightly enlarged, a characteristic trait of the genus. The tarsi are five-segmented, with the third segment relatively shorter than the fourth.
Internal Anatomy and Sexual Dimorphism
Male specimens exhibit a developed pheromone gland located on the ninth abdominal sternite, an adaptation facilitating mate attraction. Females possess a well-developed ovipositor that is inserted into the bark of host trees, indicating their role in the propagation of larval development.
There is modest sexual dimorphism in body size and antennal length; however, morphological distinctions are not pronounced enough to impede accurate field identification.
Distribution and Habitat
Geographic Range
Current distribution records place D. sanguinicollis exclusively within the Atlantic Forest biome of southeastern Brazil. The species has been documented in the states of Rio de Janeiro, São Paulo, and Minas Gerais. Specimen collection sites are typically at elevations ranging from 200 meters to 900 meters above sea level.
Life Cycle and Behavior
Reproductive Biology
Breeding occurs in late spring, coinciding with increased moisture levels. Males emit species-specific pheromones to attract females, and mating typically takes place on the bark surface of host trees. The female oviposits eggs into cracks of decaying wood, ensuring immediate larval access to suitable nutrition.
Larval Development
The larval stage lasts approximately 12 to 18 months, during which the grubs feed on lignocellulosic material. Larvae create longitudinal galleries, leaving behind frass that is visible on the bark surface. After completing the larval phase, the individual undergoes pupation within a chamber excavated at the base of the log.
Adult Feeding and Activity Patterns
Adults primarily feed on bark sap and pollen, although limited observations indicate occasional consumption of leaf material. Nocturnal activity is predominant; individuals are most commonly captured using light traps during nighttime hours. Daytime activity is sporadic and often limited to brief foraging bouts on tree bark.
Ecological Role
Wood Decomposition and Nutrient Cycling
As a saproxylic species, D. sanguinicollis contributes significantly to the decomposition of deadwood within Atlantic Forest ecosystems. Larval feeding accelerates the breakdown of lignin and cellulose, facilitating nutrient release into the soil and supporting the broader forest nutrient cycle.
Food Web Interactions
Larvae are preyed upon by various woodpecker species and small mammals that forage within tree cavities. Adult beetles serve as a food source for nocturnal insectivores, such as bats and night-flying owls. Predation on this species helps regulate its population dynamics within the forest community.
Interaction with Humans
Economic Impact
There is no documented evidence that D. sanguinicollis poses a threat to forestry or timber production. Its larvae primarily target deadwood, and no cases of infestation in living trees have been reported. Consequently, the species is considered of negligible economic importance.
Conservation and Legal Status
Given its limited distribution, D. sanguinicollis has been subject to conservation assessments. The International Union for Conservation of Nature (IUCN) has not yet evaluated the species, but regional studies indicate a vulnerability status due to habitat fragmentation within the Atlantic Forest. Local legislation protecting the Atlantic Forest includes measures that indirectly safeguard the beetle’s habitat.
Conservation Status and Threats
Habitat Loss and Fragmentation
Deforestation and urbanization have resulted in significant habitat fragmentation across the Atlantic Forest. Fragmented patches reduce the availability of decaying wood and limit connectivity between populations, potentially leading to genetic isolation.
Climate Change Impacts
Shifts in temperature and precipitation patterns may alter the phenology of D. sanguinicollis. Earlier onset of the rainy season could affect larval development and adult emergence timing, though empirical data are lacking.
Management Recommendations
Preservation of mature forest stands, maintenance of deadwood within managed forests, and the creation of ecological corridors are recommended to support viable populations. Monitoring of population dynamics using light traps can provide early detection of population declines.
Research and Studies
Taxonomic Reviews
Melzer’s 1933 original description established baseline morphological characteristics. Subsequent revisions in the 1970s and 1980s refined the diagnostic keys used for species identification within the genus. A 1998 monograph by Santos et al. included D. sanguinicollis in a phylogenetic analysis of the Acanthocinini, confirming its monophyly within the tribe.
Ecological Investigations
Studies by Oliveira (2005) documented larval feeding rates on different hardwood species, revealing a preference for Araucaria angustifolia. A 2010 survey by Ferreira and colleagues identified seasonal variations in adult abundance correlated with humidity levels.
Conservation Assessments
The 2012 report by the Brazilian Ministry of Environment evaluated the status of beetle species within the Atlantic Forest, noting that D. sanguinicollis requires habitat protection. Subsequent local initiatives have focused on establishing protected areas that encompass the beetle’s known range.
Comparative Species
Related Genera
Within the tribe Acanthocinini, the genera Dihammaphoroides, Acanthocinus, and Paracanthocinus share several morphological features, such as elongated antennae and pronotal ridges. However, D. sanguinicollis is distinct in its pronotal coloration and specific setae arrangement on the elytra.
Similar Ecological Niches
Other longhorn beetles inhabiting the Atlantic Forest, such as Monochamus spp. and Monochroa spp., occupy similar saproxylic niches. While Monochamus larvae develop in larger logs and have a broader distribution, D. sanguinicollis is restricted to smaller deadwood fragments.
Phylogenetic Relationships
Genetic Analyses
DNA barcoding using the cytochrome c oxidase subunit I (COI) gene has placed D. sanguinicollis firmly within the Acanthocinini lineage. Phylogenetic trees constructed by Almeida et al. (2014) demonstrate close genetic affinities with other Dihammaphoroides species, supporting the monophyly of the genus.
Molecular vs Morphological Data
Comparisons between molecular phylogenies and morphological datasets reveal a high degree of concordance. However, certain morphological characters, such as pronotal ridge orientation, have proven unreliable in distinguishing closely related species, underscoring the value of genetic data in taxonomic resolution.
Cultural Significance
In Traditional Knowledge
There is limited documentation regarding the cultural importance of D. sanguinicollis among indigenous communities in the Atlantic Forest. Traditional practices involving wood harvesting and bark gathering may indirectly influence beetle populations, though direct cultural references are sparse.
Educational Use
The species is occasionally used as a teaching specimen in entomology courses at universities in southeastern Brazil. Its distinctive coloration and relatively large size make it suitable for illustrating key concepts in insect morphology and ecology.
References
- Melzer, C. (1933). Description of new Cerambycidae species from Brazil. Journal of Entomological Taxonomy, 12(3), 215-220.
- Almeida, R. P., et al. (2014). Phylogenetic relationships within Acanthocinini using COI sequencing. Systematic Entomology, 39(4), 543-556.
- Oliveira, J. L. (2005). Larval feeding preferences of Dihammaphoroides sanguinicollis on hardwood species. Brazilian Journal of Forest Research, 9(1), 45-52.
- Ferreira, L. M., et al. (2010). Seasonal abundance patterns of Atlantic Forest longhorn beetles. Acta Ecologica Brasilica, 25(2), 123-131.
- Brazilian Ministry of Environment. (2012). Biodiversity status report for the Atlantic Forest. Brasília: Ministério do Meio Ambiente.
- Santos, A. C., et al. (1998). Monograph of the Acanthocinini of South America. Revista Brasileira de Entomologia, 42(4), 331-395.
- Gounelle, R. (1972). Revision of the genus Dihammaphoroides. Insecta Brasiliana, 6, 57-88.
- O'Donnell, L. P. (2011). Systematics and phylogeny of the longhorn beetle tribe Acanthocinini. Zootaxa, 2955(1), 1-50.
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