Leaf‐cutting ants (genera Acromyrmex and Atta) are the most important herbivores in the Neotropical region. Within the genus Acromyrmex, the species and subspecies Acromyrmex striatus, Acromyrmex silvestrii subsp. silvestrii and Acromyrmex silvestrii subsp. bruchi are morphologically similar to one another but differ from the rest of their congeners. Recent studies have suggested that Ac. striatus belongs to a currently undescribed leaf‐cutting ant genus. Herein, we propose a new phylogenetic hypothesis for leaf‐cutting ants based on five nuclear genes (wg, LW Rh, EF1αF1, EF1αF2 and Top1) and describe a new genus. We used colonies of Ac. striatus, Ac. silvestrii silvestrii and Ac. silvestrii bruchi collected from Brazil, Argentina, Uruguay and Bolivia, covering most of their known distribution. We constructed a molecular phylogenetic hypothesis for these three taxa using sequences from the mtDNA COI gene. The retrieved phylogenetic tree reveals that Ac. striatus, Ac. silvestrii silvestrii and Ac. silvestrii bruchi form a well‐supported clade (P.P. = 1). Through analyses of molecular phylogenetic and morphological data, we propose a new genus of leaf‐cutting ant, Amoimyrmex Cristiano, Cardoso & Sandoval, gen. nov., redescribe the species Amoimyrmex striatus (Roger, 1863) comb. nov. and Amoimyrmex silvestrii (Emery, 1905) comb. nov., and elevate Ac. silvestrii bruchi to the level of species as Amoimyrmex bruchi (Forel, 1912) comb. nov. et stat. rev.. We also provide information on the geographic distribution of Amoimyrmex, an illustrated identification key for its taxa and descriptions of all the known castes of each species, including diagnostic characteristics, high‐quality images and distribution maps. We believe that the results of this study contribute substantially to taxonomic knowledge of leaf‐cutting ants and reaffirm the complex evolutionary history of the group.
Here we use karyomorphometrical analysis to characterize and evaluate the karyotype of the turtle ant Cephalotes pusillus (Klug, 1824). This is the first representative of this diverse ant genus to be cytogenetically studied. They bear a diploid chromosome set of 44 chromosomes, which, according to the centromeric index, are metacentric, submetacentric, and subtelocentric. This small ant is quite widely distributed in the Neotropics and seems to be well adapted to living in disturbed areas. Here we report the species nesting on dead trunks used to build fences at countryside houses and farms. On these nests, we observed some never reported behavior of C. pusillus: the ants appear to be able to dig by actively removing small fragments of dead wood fiber, hence expanding their nest cavities. It was not thought that Cephalotes species had this ability, given that they nest in preexisting cavities. Our observations are initial remarks that the small plier-like mandibles of C. pusillus may not be a constraint for this species, adding to our knowledge on ant nesting biology.
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Xylographus globipennis Reitter, 1911, a ciid beetle known only from its type locality in Eritrea, has in fact a broad distribution in the Afrotropical region. A redescription of the species is provided, including the description of its male terminalia, based on the lectotype and three paralectotypes, here designated, and specimens from several localities in Democratic Republic of the Congo and in Kenya. The geographic distribution and similarities of external morphological characters of X. globipennis to other African Xylographus species are also discussed.
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