Caccothryptus

Caccothryptus is a genus of minute marsh-loving beetles in the subfamily Limnichinae. The genus was formally established (circumscribed) by the entomologist David Sharp in 1902¹, with C. compactus as the type species. In 2014, the entomologists Carles Hernando and Ignacio Ribera published a major revision of the genus, reorganizing it from seven species into twenty species in five species groups, classified mainly by similarities in genital shape. Discoveries in the following years have brought the total number of species up to thirty-four. Due to the relative lack of studies and material on Asian Limnichidae, more species are likely still to be described. Ranging from 2.5 to 5.5 mm in total length, the beetles have ovoid bodies ranging from black to brown in color. Their range extends across Southeast Asia, alongside portions of East Asia and South Asia. They generally live in water-logged dead wood adjacent to small streams.

Caccothryptus is a genus of minute marsh-loving beetles in the subfamily Limnichinae. The genus was formally established (circumscribed) by the entomologist David Sharp in 1902, with C. compactus as the type species. In 2014, the entomologists Carles Hernando and Ignacio Ribera published a major revision of the genus, reorganizing it from seven species into twenty species in five species groups, classified mainly by similarities in genital shape. Discoveries in the following years have brought the total number of species up to thirty-four. Due to the relative lack of studies and material on Asian Limnichidae, more species are likely still to be described. Ranging from 2.5 to 5.5 mm in total length, the beetles have ovoid bodies ranging from black to brown in color. Their range extends across Southeast Asia, alongside portions of East Asia and South Asia. They generally live in water-logged dead wood adjacent to small streams. ==Taxonomy== Caccothryptus is a genus of Limnichinae, a subfamily of the minute marsh-loving beetles (Limnichidae). The Limnichidae are a diverse family of beetle, absent only from alpine and polar regions, as well as most oceanic islands. They are most commonly riparian, living on the shores of rivers, although some are intertidal (living along beaches or coral formations). However, many genera are fully terrestrial, living in forest litter. Little research has been done on most genera, and the larvae and pupae of most are especially poorly documented. Most species are herbivorous. Within Limnichinae, Caccothryptus belongs to the "Mandersia group" of genera, alongside Euthryptus, Mandersia, Pseudothryptus, Resachus, and Simplocarina, all much smaller taxa in terms of species count. These genera share a number of physical features, such as a non-articulated (jointed) aedeagus (the male reproductive organ). These lack an articulated spiculum (internal piece) within the median lobe; this distinguishes them from the genus Byrrhinus. The Afrotropical genera Tricholimnichus and Cyclolimnichus are close relatives of the Mandersia group, but lack some distinguishing characteristics in the pronotum (dorsal plate of the thorax). ===Species and species groups=== All Caccothryptus species have a non-articulated aedeagus, while their parameres (side lobes of the external genitalia) can be either separated or fused. This can vary even within a species group, although all species of compactus and testudo have separated parameres. A lobe along the center of the aedeagus has a sulcus (groove), which varies between species groups. C. rouyeri, the only species of the rouyeri group, can be distinguished by lateral expansions on the median lobe of its aedeagus, while the jaechi group can be recognized by a denticled (serrated) ventral portion of this lobe. All species have microscopic glandular pores on the middle portion of the fourth sternite (one of the rear segments of the abdomen), while the jaechi and zetteli groups also have these on the sides of the fifth sternite. Males of compactus group species have dissimilar front claws, with the internal claw longer and more indented than the external. Fifteen new species of Caccothryptus have been identified since the 2014 redescription, all within the compactus and testudo groups. The current number of 34 species is likely to increase further, due to a relative lack of studies and material on Asian Limnichidae. Many species are only known from a tiny number of specimens within a small area. In terms of species count, Caccothryptus is among the largest genera of minute marsh-loving beetles, behind fellow Limnichidae genera Byrrhinus and Limnichus.

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