Strategus validus ( Fabricius 1775 )

Alvarez, Héctor Jaime Gasca, da, Claudio Ruy Vasconcelos, Fonseca & Ratcliffe, Brett C., 2008, Synopsis of the Oryctini (Coleoptera: Scarabaeidae: Dynastinae) from the Brazilian Amazon, Insecta Mundi 2008 (61), pp. 1-62 : 52-56

Strategus validus ( Fabricius 1775)

( Fig. 102-106 )

Scarabaeus validus Fabricius 1775: 6

Scarabaeus tricornis Jablonski 1785: 269 (synonym)

Scarabaeus validus Fabricius 1787: 4 (redescription)

Oryctes faunus Billberg 1820: 383 (synonym)

Strategus tridens Burmeister 1847:133 (synonym, nomem nudum)

DESCRIPTION. Length: 31.1-49.6 (males); 41.7-43.6 (females). Width: 15.1-24.4 mm (males); 21.9-23.5 (females). Color: Reddish brown to black.

Males. Head: Frons with surface rugose to punctate, with 2 conical, widely separated tubercles. Eye canthus with surface rugose, apex rounded. Clypeus with apex broadly truncate, occasionally with notch at center, reflexed. Antenna with 10 segments, club subequal in length to segments 2-7. Mandibles with 3 lobes; basal lobe small, apex rounded; middle lobe large, subtriangular, apex rounded; apical lobe small, triangular. Pronotum: Base with rugopunctate band, band reduced to basal bead at middle. Sides with small, deep punctures. Majors ( Fig. 102 ) with anterior long, slender, forward curving horn, apex rounded. Posterior horns long, stout, laterally compressed, apex rounded, slightly divergent. Minors with anterior horn short, conical, apex strongly rounded. Posterior horns short, triangular, laterally compressed, subparallel. Elytra: Sutural stria strongly impressed, crenulate. Surface punctate, punctures small. Lateral half of disc with incomplete striae. Sides with punctures, usually with 1-5 rows of ocellate, moderately deep punctures behind humerus ( Fig. 103 ). Apex strongly punctate. Pygidium: Surface granulate, finely punctate, punctures small. In lateral view, convex. Legs: Protibia quadridentate. Apex of posterior tibia with 2 teeth, occasionally with 3, median tooth with apex strongly rounded. First tarsomere of posterior tarsus triangular, apex extended into long spine. Venter: Prosternal process long, stout, apex densely setose. Parameres: Oval, narrow, apex weakly dilated, setose, usually subparallel ( Fig. 104-105 ).

Females. As males except in the following respects: Head: Frons with surface rugose. Clypeus with apex truncate to subtruncate, surface punctate. Mandibles smaller in size, lobes with apex rounded. Pronotum: Surface of anterior half rugose. Sides moderately punctate, punctures small to large. Fovea deep, surface rugose. Elytra: Surface of sides with incomplete rows of punctures behind humerus. Pygidium: Surface strongly granulate. Posterior margin with band of smaller setae. Apex with 2 bands of small setae. In lateral view, basal half convex, apical half concave.

DIAGNOSIS. Strategus validus is separated from S. aloeus by the rows (1-5) of ocellate, deep punctures behind the humerus, clypeus broadly truncate, and the characteristic shape of the parameres.

DISTRIBUTION. Strategus validus is restricted to South America and is widely distributed in Brazil, Argentina, Paraguay, and Uruguay ( Ratcliffe 1976).

LOCALITY RECORDS. ( Fig. 106 ) 18 specimens examined (5 males, 13 females). Specimens were seen from the following collections : INPA, CZPB, MZSP, MPEG.

ACRE (1): Tarauacá (Rio Tarauacá). AMAZONAS (9): Benjamin Constant (Rio Javari), Coari (Rio Urucu), Itacoatiara, Novo Airão (Ajaru), Presidente Figueredo (UHE-Balbina), Tefé. PARÁ (6): Belém, Itaituba (Parque Nacional Amazônia), Melgaço Caxiuanã (Estação Científica Ferreira Penna), Santarém. RONDÔNIA (1): Porto Velho (Rio Madeira).

TEMPORAL DISTRIBUTION. February (3), June (1), July (7), August (1), September (2), October (2), December (1).

BIOLOGY. Little is known about the life history of S. validus . Adults are nocturnal and are attracted to lights. Larvae has been collected from large, dead tree trunks ( Costa et al. 1988). Gonçalves (1946) observed adults attacking the base of young “carnauba” plants, Copernica cerifera . Pereira et al. (1977) conducted studies about the penetration depth of S. validus in sandy soils. Quinderé et al. (1977) observed that the larvae of S. validus attack young coconut palms in the northeastern Brazil, making irregular galleries and penetrating the base of the plant toward the stem.

In Brazilian Amazonia, adults have been collected from ombrophilous forests and areas of seasonal whitewater inundation forest (várzea) at elevations ranging from sea level to 200 meters.

General Remarks

The results of this study were based on the examination of 1532 specimens, that included 7 genera, 18 species, and 2 subspecies. Five of these species are reported for the first time from Brazilian Amazonia. The material examined represented 7 states, 97 provinces, and approximately 167 localities in the study area.

Overall, the tribe Oryctini shows a wide distribution in the Brazilian Amazon. The distribution data suggests the states with the highest oryctine diversity were Amazonas and Pará, with 17 and 13 species respectively; these states also had the greatest number of localities recorded. Amapa and Mato Grosso had fewer species, with 4 species each. The states of Tocantins and Maranhão had no records, but this probably reflects little or no collecting effort ( Table 1).

Coelosis biloba , Strategus aloeus and Enema pan have broad distributions and are considered common species in Brazilian Amazonia. They have all been recorded from seven states in the study area ( Table 1). These species have a wide distribution in the Neotropics, some ranging from the southern United States to northern Paraguay. They seem to be ecological generalists inhabiting various types of mountain ecosystems, humid forests, savannah environments, and even agroecosystems ( Endrödi 1985; Ratcliffe 2003; Ratcliffe and Cave 2006).

The faunistic survey of Oryctini in Brazilian Amazonia, confirmed the high biodiversity of this large area of tropical forest. Compared with other faunistic surveys conducted in the Neotropics, the Brazilian Amazon contains more species of Oryctini than Costa Rica and Panama together, or that of El Salvador, Honduras and Nicaragua together, and more than half of the species known from Mexico ( Table 2).

One hypothesis that explains the diversity and distribution patterns of Amazonian biota is the refuge theory, where several dry climatic periods of the Pleistocene and post-Pleistocene reduced the Amazon forest to smaller, disjunct forests, which served as refugia for populations of animals which then differentiated from one another during these periods of geographic isolation. The isolated areas later expanded again during periods of humid climatic conditions, thus permitting the refuge area populations to extend their ranges. This process of separation and connection of forests was repeated several times, which favored high speciation in successive periods of ecological isolation ( Haffer 1969; Vuilleumier 1971). Conversely, Amorim (2001), suggested the refuge theory does not offer a general method for biogeographic reconstruction, and the succession of climatic cycles as the chief cause of speciation cannot explain the patterns of distribution in the region.

Another fact that influenced speciation in Amazonia was the interglacial periods of sea transgression in the Amazon basin in the Pleistocene. This resulting complex network of rivers served as an active barrier that prevented the dispersal of organisms ( Wallace 1852). This may have been responsible for subspeciation of Strategus surinamensis into S. surinamensis hirtus distributed south of the Amazon River and S. surinamensis surinamensis north of the Amazon River ( Ratcliffe 1976). A similar situation may be happening with Heterogomphus telamom , whose geographical distribution is in northern Amazonia ( Fig. 38 ) and Heterogomphus ulysses with records south of the Amazon River ( Fig. 45 ).

The Amazon is considered a biogeographical heterogeneous area, where animal and plant communities are different and form a mosaic of separate areas of endemism delimited by major rivers, each with its own evolutionary history ( da Silva et al. 2005). These smaller areas of endemism are the biogeographical units best suited for analysis of historical biogeography, and they are important for the formulation of hypotheses about the processes responsible for the formation of regional biotas ( Morrone 1994; Morrone and Crisci 1995). Currently it is generally accepted that the biotic diversity of Amazonia is related directly to historical factors that influenced the emergence of areas of endemism (Amorim 2001).

The geologic history of the Amazon region is another factor that may explain the diversity and distributional patterns of plant and animal species. Botanical and geological studies showed that the complex geological history of the Amazon created areas with different edaphic conditions that support communities of different species ( Räsänen et al. 1992, 1995). The conditions of soil, determined by climate and geological processes, are clearly related to the patterns of distribution of various groups of plants such as Passifloraceae ( Gentry 1981) , trees ( Tuomisto et al. 1995), Pteridophyta ( Tuomisto and Poulsen 1996, 1998), and Melastomataceae ( Ruokolainen et al. 1997) . Some of these soil areas coincide or are within the areas of endemism for some terrestrial vertebrates ( da Silva et al. 2005), birds ( Haffer and Prance 2001), amphibians ( Ron 2000), primates ( Silva and Oren 1996), and forest butterflies ( Hall and Harvey 2002), thus indicating some degree of congruence for patterns of distribution of different taxonomic groups.

Although the Amazon is considered a biodiverse region, some genera of neotropical Oryctini are more diversified in southern South America The genus Coelosis , with seven species, has two species recorded in the Brazilian Amazon, as well as Colombia and Venezuela, while the other five species are distributed from southern Mato Grosso to Argentina. A similar situation occurs with Heterogomphus species with four of the 42 species occurring in the Neotropics being recorded from the Brazilian Amazon, while the other 38 species are distributed in Central America, the Andean countries of South America, and from southern Brazil to Argentina. The relative lack of dynastine species in the Amazon region may be an indicator of a re-colonization pattern from both the north and the south of the Amazon River as the inland Amazonian sea retreated. See, for example, Strategus species ( Ratcliffe 1976) , where only four species of 31 are distributed in Amazonia.

Figures

Figure 38. Distribution of Heterogomphus telamon in Brazilian Amazonia.

Figure 45. Distribution of Heterogomphus ulysses in Brazilian Amazonia.

Figure 106. Distribution of Strategus validus in Brazilian Amazonia.

Figure 102-105. Strategus validus. 102) Male head and pronotum (scale line: 5 mm). 103) Elytra (lateral view). 104) Parameres frontal view. 105) Parameres lateral view (scale line: 1 mm).