44 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO7 



with the border of the cranium which takes the form of a small 

 V-shaped notch. Thence the suture continues over the front of the 

 head where it forms a large, inverted V posterior to the antennae." 

 This description can best be followed by reference to a side view of 

 the head (fig. 15 C). Beginning at the mandibular articulation (c) 

 the alleged suture "coincides with the border of the cranium" to the 

 point d; here it jumps the subantennal bar (which is the true lower 

 lateral margin of the cranial wall, but is conveniently interrupted in 

 Ferris' illustration, fig. 11 A), and then turns forward along the edge 

 of the postantennal membrane to e, whence it runs mesally and 

 posteriorly on the dorsal surface of the head as the line b, forming "a 

 large, inverted V." To the writer it is quite incomprehensible how 

 such diverse elements strung together can be even imagined to con- 

 stitute a "suture." Yet, Ferris designates this variously composed 

 line the "great suture of the head," and furthermore asserts that it is 

 "evidently the suture between the mandibular and antenna! segments." 

 An examination of other species of Symphyla gives no evidence of the 

 existence of any such suture, even the V-lines on the head being 

 absent (D). 



The symphylid head in its essential structure is identical with the 

 head of a diplopod (cf. fig. 15 C and D with E). The lateral margin 

 of the cranium below the postantennal membrane containing the 

 organ of Tomosvary (OT) is a narrow bar in Scutigerella (C), 

 forming a sharp angle {d) with the ascending margin above the 

 mandibular articulation (c). The same structure is seen in Hanseniella 

 (D), but here the subantennal bar of the cranium is wider; in the 

 diplopod (E) the same part is a broad sclerotic area below the 

 antenna and the organ of Tomosvary. The deep notch of the lateral 

 cranial margin is characteristic of both Symphyla and Diplopoda, 

 but while it is entirely occupied by the mandible in the diplopods (E, 

 Md), in the symphylids (C, D) a membranous area containing the 

 head spiracle (Sp) intervenes between the mandible and the edge of 

 the cranium. The symphylid head, in fact, has no structural likeness 

 to an insect's head; it is clearly a slightly modified diplopod head, 

 or vice versa. The structure of the head, the presence of a large, 

 independently musculated gnathal lobe on the mandible, and the 

 anterior position of the genital openings link the Symphyla with the 

 progoneate Diplopoda. 



SUMMARY 



1. The insect cranium is not composed of "plates" united by 

 "sutures." 



2. Most of the so-called sutures of the head are lines of cuticular 



