Smaller appendages (such as the stylets of male cockroaches) may be carried on the ninth segment.
The appendages of the abdomen are called cerci, stylets and gonapophyses.
The stylets, when present, are placed on the ninth segment, and in some Thysanura exist also on the eighth segment; their development takes place later in life than that of the cerci.
Whether cerci, stylets and gonapophyses are developed from these rudiments has been much debated.
It appears that it is possible to accept cerci and stylets as modifications of the temporary pseudopods, but it is more difficult to believe that this is the case with the gonapophyses, for they apparently commence their development considerably later than cerci and stylets and only after the apparently complete disappearance of the embryonic pseudopods.
But another and apparently insuperable objection may be raised - that the appendages of the ninth segment are the stylets, and that the gonapophyses cannot therefore be appendicular.
Metanemertini, in which the nervous system lies inside the dermal muscles in the parenchyma; the mouth lies in front of the level of the brain; the proboscis as a ru'e bears stylets; the intestine nearly always has a caecum.
Heteronemertini, in which the dermal musculature is in three layers, an external longitudinal, a middle circular, an internal longitudinal; the nervous system lies between the first and second of these layers; the outer layer of longitudinal muscles is a new development; there is no intestinal caecum; no stylets on the proboscis and the mouth is behind the level of the brain.
The significance of two or more (in Drepanophorus very numerous) small sacs containing so-called " reserve " stylets resembling in shape that of the central dart is insufficiently known.
The latter are the cutting or piercing stylets (fig.
5, B) on which the stylets work, tongues or rails on the " guide " fitting accurately into longitudinal grooves on the stylet.
But the wings vary considerably in different families, and the most distinctive feature is the structure of the jaws, which form a beaklike organ with stylets adapted for piercing and sucking.
The point of the rostrum is pressed against the surface to be pierced; then the stylets come into play and the fluid food is believed to pass into the mouth by capillary attraction.
The mouth, situated at the opposite end and armed with a pair of stylets, leads into an oesophagus, into which the ducts of a pair of so-called salivary glands open.
It is frequently armed with spines, hooks or stylets, and is further complicated by the addition of a nutritive secretion (the prostate gland) which may open at its base or pass separately by a special duct to the exterior.
There may also be abdominal appendages - in the form of simple unjointed stylets (fig.
In parasitic bloodsucking forms the mandibles often have the shape of piercing stylets, and are enclosed in a tubular proboscis formed by the union of the upper lip (labrum) with the lower lip (hypostome or paragnatha).