Class of Subphylum Uniramia - Symphyla

Symphyla is yet other small myriapodous group that includes around 160 described species. These are also soil living forms and live in leaf molds also. They measure approximately 1 to 8 mm in length and have a trunk Lade of 13 segments but 15-22 tergal plates. Only 12 segments bear a pair of legs each and the 13^th segment bears a pair of cerci or spinnerets. The 13^th segment as well bears a pair of sensory, hairs called trichobothria. These animals can run fast through humus. The hunk terminates in a tiny telson. Mouth parts include a pair of mandibles two pairs of maxillae of that the second pair of maxillae is fused to make labium. A pair of spiracles opens, on every side of the head and the trachea arising from them supplies only the first three segments. Eyes are not present but a pair of Tomosvary's organs is present. Symphylans show peculiar copulatory behavior. The males deposit 150 to 450 spermatophores which are swallowed by the female. There are stored in particular buccal pouches. Then she releases the eggs through a single gonopore located on the ventral surface of the fourth segment. The eggs are attached to the substratum and the sperms are smeared over the eggs through the female to fertilize them. Development is anamorphic. Parthenogenesis is as well common in Symphylans e.g. Scutigerella.