382 SUBANTARCTIC ISLANDS OP NEW ZEALAND. [Cdlftnbota. 



EXPLANATION OF PLATE XVIIL 



Fig. 1. Triacanthella alba, side view. Magnified 60 diameters. The head and the 2nd and 6th ab- 

 dominal segments are shown externally ; the rest of the insect in optical section, to display 

 the musculature and portion of the digestive tract. <j, gullet (fore gut) ; s, stomach (mid- 

 gut) ; in, intestine (hind gut) ; d, dorsal, I, lateral, and v, ventral, longitudinal muscles ; 

 p, vertical, and o, oblique, dorso-ventral muscles ; e, extensors, and /, flexors, of spring. 



Right half of head, showing ocelli, post-antennal organ, and feeler. Magnified 218 diameters. 



Left post-antennal organ of the same specimen. Magnified 404 diameters. 



Right post-antennal organ of another specimen. Magnified 404 diameters. 



5. Sense-organ on 3rd antennal segment. Magnified 809 diameters. 



Sense-organ on 4th antennal segment. Magnified 809 diameters. 



The three anal spines, seen from the dorsal aspect, somewhat obliquely. Magnified 121 

 diameters. 



Right mandible, with its retractor muscle, front view. Magnified 404 diameters. 



Distal part of left mandible, antero-internal view. Magnified 404 diameters. 



Right maxillula (a) ; tongue (6) ; left maxilla and " palp " (c) : front view, the left maxillula 

 having been removed to expose the tongue, cr, cardo ; si, stipes ; h, outer process of head ; 

 la, anterior, and la', posterior, lamellae of head ; It, ligament uniting maxilla with base of 

 maxillula ; j), palp ; pe, foot of tongue. Magnified 404 diameters. 



Distal end and stipes of right maxilla, postero-internal view. References as in fig. 10. Magni- 

 fied 564 diameters. 



Labium and adjacent cuticle. Magnified 404 diameters. 



Fig. 13. Hind leg, tibial segment with claw, empodium, and vestigial appendix (ap). Magnified 



218 diameters. 



Fig. 14. Catch, side view, i . 



„. , _ , . • 1 Magmfied 564 diameters. 



Fig. 15. „ front view. I ° 



Fig. 16. Spring : lateral view of end of manubrium, and conjoined dens and mucro. Magnified 356 

 diameters. 



Fig. 17. The same from a young individual. , 



„. ,„ „ • Magnified 356 diameters. 



rig. 18. „ very small specimen, i 



