Hemianamorphosis
Guides
Polyxenus lagurus
Bristly Millipede
Polyxenus lagurus, commonly known as the bristly millipede, is a small millipede species distinguished by its detachable defensive bristles that entangle attacking ants and spiders. It exhibits a unique reproductive polymorphism, with some populations reproducing sexually and others parthenogenetically. This species undergoes hemianamorphosis, adding segments and legs through juvenile molts until reaching a fixed adult complement of 13 leg pairs and 10 tergites, after which molting continues without further segment addition. It is the most common polyxenid in Europe and the only representative of order Polyxenida in the British Isles.
Symphyla
Symphylans, Garden centipedes, Pseudocentipedes
Symphylans are small, cryptic, soil-dwelling myriapods that resemble centipedes but are non-venomous and only distantly related. They range from 2 to 13 mm in length, lack eyes and pigment, and possess 12 pairs of legs as adults. These arthropods are rapid runners that move through soil pores and are found from the surface to depths of about 50 cm. More than 200 species are known worldwide, with populations reaching up to 88 million per acre in favorable conditions.