THE LEGS AND LEG-BEARING SEGMENTS OF SOME 



PRIMITIVE ARTHROPOD GROUPS, WITH NOTES 



ON LEG-SEGMENTATIO'N IN THE ARACHNIDA 



By H. E. EWING 



Federal Bureau of Entomology 



(With 12 Plates) 



CONTENTS 



PAGE 



Introduction 2 



The primitive arthropod appendage 3 



The primitive arachnid leg 4 



Legs of Solpugida 4 



The leg segments of primitive phalangids 6 



The leg segments in some of the Acarina 7 



Leg-segmentation in various arachnid groups with special reference to 



the Pseudoscorpionida 8 



The Pycnogonida and Ricinulei 10 



Conclusions in regard to arachnid limbs 11 



Leg-segmentation and musculature in the Protura 12 



Leg-segmentation and musculature in Pauropoda 14 



The so-called coxal appendages in Pauropiis 15 



The Pauropus type of leg 16 



Leg-segmentation and muscle attachments in Symphyla 16 



The coxal appendage in Symphyla 18 



The legs in Thysanura 18 



Remarks on the thysanuran type of leg 20 



The nature of the coxal appendage in the Machilidae 20 



The leg segments of Collembola 20 



The collembolan type of leg 22 



The primitive type of tarsal claws in Insecta 22 



Postcephalic body-segrrtentation in Arthropoda 24 



The first body segment of Symphyla 25 



The first body segment in Pauropoda 25 



Evidence of a cervical segment among insects 26 



The segments included in the insect thorax 26 



Abdominal segmentation 27 



The doubling of body segments 27 



Embryonic reduction of abdominal segments 28 



The tergal plates of the leg-bearing segments 28 



Conclusions regarding the terga of leg-bearing segments of primitive 



arthropods 3° 



SmithsonianIMiscellaneous Collections, Vol. 80, No. 11 



I 



