The internal anatomy and histology of the larva of the fish mite Lardoglyplius konoi are described from paraffin, serial sections eut at six microns thickness and viewed under immersion lens. In addition to a well formed body wall, the larval stages have well defined muscular system, digestive system and nervous system. The reproductive organs are only in the rudimentary stage. The digestive system has ail the components as in the adult and it is functional as indicated by specialised regions in the epithelium of the walls. The epithelium in the anterior part of the caeca contains characteristics spherules. The nervous system has a supra-oesophageal ganglion, circumoesophageal connectives and a ventral cord. Bilateral fusion of the supra-oesophageal ganglion is not so complete in the larva as in the adult or the nymphal stages. The cell rind is not grouped into separate ganglia on the ventral cord. A cluster of cells on each side of the rectum ·.vithout any specialised inclusions forms the rudiment of the reproductive system.