Tisamenus polillo
Tisamenus polillo is a species of stick insect in the family Heteropterygidae native to the Philippine islands of Luzon and Polillo.
Description
Tisamenus polillo is a medium-sized, slender, and sparsely spined Tisamenus species. Females grow to in length. Their mesothorax has three more or less prominent mesopleural spines, while females of the morphologically similar, but larger species Tisamenus draconinus and Tisamenus napalaki have four, and Tisamenus lachesis has five. The anterior of the three spines is only moderately sharp. The metathorax has a distinct metapleural spine, above which is a much smaller tubercle or spine seat. The edges of the triangle on the mesonotum, typical of the genus, are raised and spineless in both sexes. Small, paired spines are found on terga two to four of the abdomen. In the females of the smaller Tisamenus charestae, only small tubercles are visible here. Furthermore, the supracoxal spines of the mesopleurae and metapleurae are developed as short, conical tubercles rather than as spines like in the females of Tisamenus polillo. The lower part of the ovipositor, known as the subgenital plate, projects only slightly beyond the upper part, the epiproct, in Tisamenus polillo, while in Tisamenus charestae it exceeds it by more than half its length.Males of Tisamenus polillo reach a length of. They are slimmer than males of Tisamenus lachesis. While these males always have five mesopleural spines, males of Tisamenus polillo have a maximum of four such spines, which may be reduced to the posterior supracoxal spine located at the level of the midlegs. The pronounced metapleural spine, also present in females, is found on the metathorax. They differ from the equally slender males of the smaller Tisamenus kalahani in their more pronounced head and body structures. For example, males of Tisamenus polillo have large, spiny supraorbital spines on their heads and prominent two- or three-spined anterior spines on the pronotum, while those of Tisamenus kalahani have one spine. The spiny mesopleural and metapleural spines prominent in Tisamenus polillo are recognizable only as conical tubercles in Tisamenus kalahani. The anterior angles of the triangle on the mesonotum are spineless in Tisamenus kalahani, whereas they bear spines in Tisamenus polillo. On terga two and three of the abdomen, Tisamenus polillo has small, paired spines, which are missing in Tisamenus kalahani.
The eggs of Tisamenus polillo are long, wide, and high. They are similar in shape to those of Tisamenus draconinus, but not as wide. The micropylar plate, at long, reaches about three-quarters of the capsule length. Its three processes are relatively broad and, as is typical for the genus, form an upside-down Y.