CHARACTERISTICS OF INSECTS AND THEIR RELATIVES 19 



Fig. 24. Eurypanropus spino- 

 sus; face showing the base of 

 the antennas, the mandibles, 

 and the eye-like spots (After 

 Kenyon) . 



of jaws, there is a horny framework forming a kind of lower lip to the 

 mouth (Fig. 25). The homologies of the mouth-parts with those of 



the allied classes of arthropods have not 

 been determined. 



The body-region consists of twelve 

 segments. This is most clearly seen by 

 an examination of the ventral aspect of 

 the body. When the body is viewed from 

 above the number of segments appears to 

 be less, owing to the fact that the terga of 

 the first ten segments are fused in 

 couples. Nine of the body-segments bear 

 well-developed legs. The appendages of 

 the first segment are vestigial, and the 

 last two segments bear no appendages. 

 The most distinctive feature of mem- 

 bers of this class is the form of the 

 antennas, which differ from those of all 

 other arthropods in structure. Each 

 antenna (Fig. 26) consists of four short 

 basal segments and a pair of one-jointed 

 branches borne by the fourth segment. 

 One of these branches bears a long, many- 

 ringed filament with a rounded apical 

 knob; and the other branch bears two 

 such filaments with a globular or pear- 

 shaped body between them. This is prob- 

 ably an organ of special sense. 



The pauropods live under leaves and 

 stones and in other damp situations. 

 Representatives of two quite distinct families are found in this 

 country and in various other parts of the world. In addition to these 



a third family, the 

 Brachypauropodida;, 

 is found in Europe. 

 In this family the 

 pairs of terga consist 

 each of two distinct 

 plates. Our two 



. families are the fol- 



Mg. 26. Antenna of Eurypauropus spinosus 



(After Kenyon). lowing: 



Fig. 25. Mouth-parts of Eury- 

 pauropus ornatus; md, man- 

 dible; mx, second iaws; /, 

 lower lip (After Latzel). 



