Tisamenus lachesis is a stick insect species (Phasmatodea), in the family of the Heteropterygidae endemic to the Philippine islands Luzon, Samar and Polillo.
Description For a long time, only males were known of this Tisamenus species. Like Tisamenus draconinus and Tisamenus hystrix, it is relatively spiny. As with these, there are distinct, relatively sharp spines on the posterior mesonotum (posterior mesonatals) and smaller, blunter ones in the middle of the metanotum (median metanotals). The triangle on the mesonotum typical of the genus is significantly longer than it is wide at the front in Tisamenus lachesis, while it is as wide as it is long in Tisamenus hystrix. In both species the anterior corners of the triangle end in single spines, while in Tisamenus draconinus they end in compound spines. The species is considered to be very variable. The males grow to about 4.15 to 5.1 centimetres (1.63 to 2.01 in) long and are initially reddish-brown in color with little patterning, which becomes darker with age. On the head there is a pair of spines pointing upwards. On the pronotum there are three pairs of distinct spines arranged in a group that runs diagonally outwards. On the sides of the elongated mesothorax there are five distinct spines each, and on its upper side there is an isosceles triangle formed by raised edges. The base of this triangle is attached to the front edge of the mesonotum, is strongly raised and has spines at the corners. On each side of the metathorax there are three spines each, the length of which increases from front to back. In extension of the rear tip of the triangle of the mesonotum there is a longitudinal ridge on the metanotum. On this, there can be two closely spaced tubercles on the rear edge of the meso- and metanotum, which can rarely be formed as short, blunt spines. The abdomen is slender and almost cylindrical. On its second to fifth segments there is a pair of spines pointing diagonally to the side, the length of which decreases from front to back. On these segments there can also be medium-sized spines, which are significantly smaller or barely recognizable. The females are about 6.0 to 6.2 centimetres (2.4 to 2.4 in) long. The number and arrangement of the body structures and spines is identical, although all spines are much shorter and blunter as in males. The thorax becomes evenly wider from the prothorax to the metathorax, just as the abdomen gradually becomes narrower towards the end, so that the body appears slightly convex on both sides when viewed from above. The abdomen ends in a relatively short ovipositor. Their coloration is much more variable than that of the males. In addition to the dominant brown tones, a high-contrast pattern of light beige and black tones is particularly common in newly adult females. These are more pronounced on the thorax than on the abdomen, which is usually only brown and black. With increasing age, this pattern loses contrast.
Distribution and way of life The species was described from a male on the island of Pollilo. All other records come from the islands of Samar and Luzon. On Samar, it was found in the province of Northern Samar, while on Luzon, where the species is locally very common, records have been documented from the provinces of Aurora, Isabela, Quezon, Sorsogon, Bulacan, and Laguna. There they were found on ground-covering plants at a maximum height of 20 centimetres (7.9 in). The females lay an egg in the ground several times a week. The eggs are 5.1 millimetres (0.20 in) 5.1 mm long and 2.8 millimetres (0.11 in) high, brown and hairy. The lid (operculum) sits on the egg at an opercular angle of about 20°. The micropylar plate forms an inverted Y, as in many Obriminae. When the nymphs hatch, they are about 15 millimetres (0.59 in) long, slender and brown in color. While the males remain slender and gradually develop their later shape and color over the course of the next molts, the female nymphs become noticeably broader and more contrasting in color until they show their maximum pattern and color variation as subadults. As adults, both sexes can live for more than a year.
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