CLASSIFICATION OF ONISCUS
PHYLUM :- ARTHROPODA (Jointed appendages.)
CLASS :- CRUSTACEA (Exoskeleton thick, antennae 2 pairs, jaws 3 pairs.)
SUB-CLASS :- MALACOSTRACA (Free-living Crustacea with compound eyes, biramous antennules. mandibles. 8 thoracic and 6 abdominal segments having appendages.)
ORDER :- ISOPODA (Carapace absent; body dorsoventrally flattened.)
GENUS :- . Oniscus (The wood louse or saw bug)
GEOGRAPHICAL DISTRIBUTION
It is found in Europe.
HABIT AND HABITAT
Oniscus is found in dry places under head stones, leaves, dead trees and beneath matted vegetation. It is unique among Crustacea for its perfect adaptation to terrestrial life and it feeds on decaying vegetation.
GENERAL CHARACTERSTICS OF ONISCUS
- Commonly called as wood louse or saw bug.
- Body is broad, oval and dorsoventrally compressed with granulated or tuberculated surface having deep slate colour and white spots.
- Body is divided into head, thorax and abdomen.
- First thoracic segment is fused with head forming cephalothorax, which is devoid of dorsal carapace. Compound eyes are sessile.
- Appendages are rudimentary antennules, uniramous and prominent antennae, labrum and mandibles.
- Fused thoracic segments contain maxillepedes visible on ventral side. Rest of the thoracic segments have walking legs.
- First 5 abdominal segments contain pleopods and the last abdominal segments fused with telson.
- Thin vascular abdominal pleopods functioning as gills.
- Pleopods have trachea like respiratory tubes.
- It breeds in warm months. The young develop in a brood pouch and emerge in form much like the adults except in size.
IDENTIFICATION
The animal contains two reduced abdomen, reduced pleopods and all above features, hence it is Oniscus.
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