CHARA CTERISTICS OF INSECTS A ND THEIR RELA TI VES 23 



The body of the adult measures an inch or a little more in 

 length. It is difficult to obtain perfect specimens, as they shed 

 their legs when seized. 



Class SYMPHYLA 



The Symphylids 



The members of this class are small 

 arthropods in which the head is distinct, and 

 the segments of the body form a single con- 

 tinuous region. Most of the body-segments 

 bear a single pair of legs. The antenncB are 

 very long and many-jointed. The head bears 

 a Y-shaped epicranial suture, as in insects. 

 The opening of the reproductive organs is in 

 the third segment behind the head. 



The class Symphyla includes a small 

 number of many-legged arthropods which 

 exhibit striking affinities with insects, and 

 especially with the Thysanura. The body 

 is centipede-Hke in form (Fig. 31). The 

 head is distinct, and is not bent down 



Fig . 31. — Scolopendrella 

 (After Latzel). 



as it is in the diplopods and pauro- 

 pods; it is shaped as in Thysanura and 

 bears a Y-shaped epicranial suture. The 

 body-region bears fifteen terga, which are 

 distinct, not grouped in couples as in the 

 two preceding classes; and there are 

 eleven or twelve pairs of legs. 



The antennae are long and vary greatly 

 in the number of the segments. There are 

 no eyes. The mandibles, the "maxillulae" 

 (paragnatha) , the maxillae, and the sec- 

 ond maxillae or labium are present. 



Fig. 32. — Mouth-parts of 

 Scolopendrella seen from 

 below; md, mandible; mx, 

 maxillae; s, stipes; p, pal- 

 pus; /, second maxillee or 

 labium. The mandible on 

 the right side of the figure 

 is omitted (After Hansen). 



The mandibles (Fig. 32, md) are two- 

 jointed; the maxillulcB (Fig. 33, m) are 



small, not segmented, and are attached to a median lobe or 

 hypopharynx (Fig. 33, h); they are hidden when the mouth-parts 

 are viewed from below as represented in Figure 3 2 ; the maxillce (Fig. 



