Tisamenus irenoliti

Tisamenus irenoliti is a medium-sized Tisamenus species. Due to its elongated body shape, the species resembles Tisamenus lachesis and Tisamenus polillo, native to Luzon and Polillo Islands.

Males of Tisamenus irenoliti reach a length of 38.7 to 39 millimetres (1.52 to 1.54 in), making them smaller and somewhat stockier overall. Their mesothorax is more trapezoidal and gradually widens posteriorly. They lack the enlarged spine found in Tisamenus lachesis at the two anterior corners of the mesothorax triangle typical of the genus. This triangle is significantly shorter than half the length of the mesonotum. The femura and tibiae of the hind legs have more numerous, more distinct, and more pointed ventral teeth.

The only known adult female Tisamenus irenoliti is 54.7 millimetres (2.15 in) long. It differs from Tisamenus lachesis females in the weakly developed or absent anterior pleural spine and the curved edges of the triangle on the mesonotum, which lacks the spiny, extended anterior corners. As in the males, there are more pronounced teeth on the tibiae of the hind legs and larger teeth on the edges of the foreleg femurs. The female is somewhat stockier than those of Tisamenus polillo and has four pleural spines on the mesothorax, whereas Tisamenus polillo has only three. In this female, too, the generic triangle does not extend to the middle of the mesonotum. There are two pronounced spines on the metapleurae, which are missing in the females of Tisamenus polillo. Overall, the pleural spines on the mesonotum and metanotum, as well as the head and body structures, are blunt and cone-like rather than pointed and spiny. The second known, but still juvenile female is 45 millimetres (1.8 in) long and is presumably in the penultimate stage. Its body structures are significantly more pointed and spiny than those of the described adult female. Similar to Tisamenus polillo, their appearance could also vary greatly in Tisamenus irenoliti.^[2]