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The three divisions of the digestive tract are as in insects, the epithelium of the mid-gut being histologically as in Campodea and Japyx; rectal glands are present. A pair of very large salivary glands are situated in the first to the fourth trunk-segments, consisting of a glandular portion with its duct, which unite into a common duct opening on the under side of the head, probably in the labium.

But a single pair of stigmata is present, and these are situated in the front of the head, beneath the insertion of the antennæ and within the stipes of the mandibles; the tracheæ are very fine, without spiral threads (tænidia), and mostly contained within the head, two fine branches extending on each side into the second trunk-segment.

After birth the body increases in length by the addition of new segments at the growing point.

In respect to the nervous system, there are no diagnostic characters; there are, however, not as many as two pairs of ganglia to a segment. The brain is well developed, sending a pair of slender nerves to the small eyes. The ganglia of the segment bearing the first pair of legs is fused with the subœsophageal ganglion. Grassi was unable to detect a true sympathetic system, but he suspects the existence of a very small frontal ganglion.