TRACHEATA 315 
number of segments. Some members of the family GEOPHILIDAE 
are phosphorescent, and secrete from certain glands on the 
ventral surface a luminous slime; since this is produced by 
both male and female, and neither of them has eyes, the 
secretion is regarded as a means of frightening or warning off 
enemies. The male Geophilus spins a web, and drops a sperma- 
tophore in the middle of it, and the female comes and fertilises 
herself. Geophilus longicornis is common in Britain; the 
female coils herself up and sits on her eggs, and is stated not 
to leave them until they are hatched. Cryptops hortensis, with 
twenty-one pairs of legs, is also British. 
Scutigera has very long antennae and legs, the latter in- 
creasing in length at the posterior end (Fig. 179). This genus 
has facetted compound eyes, and its tracheal system is peculiar ; 
the stigmata are median and dorsal, one for each segment, 
opening in a notch at the posterior edge of each tergum. 
Certain species produce a rattling noise by rubbing their legs 
together. 
Order 2, DIPLOPODA (Chilognatha). 
CHARACTERISTICS.— The members of the second sub-order of the 
Myriapoda are characterised by their bodies being cylindrical 
or subcylindrical, and their antennae short, of seven segments 
only. Except at the anterior end, the segments bear two parrs 
of legs, and the bases of the legs are near together ; there are 
also two pairs of stigmata on every segment. The generative 
aperture is at the base of the second or third pair of legs. 
A 
Fra. 180.—Ventral view of Polyxenus lagurus (after Bode) much enlarged, actual 
length a little over ;4;th of an inch. 
a. Position of genital openings. 
The Diplopoda are all vegetable feeders, and have no 
poison claws. The genus Polyxenus is somewhat intermediate 
