Carpenter and Pollard — Lateral Spiracles in Hypoclerma Larva. 83 



EXPLANATION OF PLATES. 

 Plate VIII. 



Fio. 



1. Hypoderma bovis. Fourth-stage larva. Lateral view, x 5. 



a. s., anterior spiracle ; /. s., 1-6, lateral spiracles ; p. s., posterior 

 spiracles ; p.g., suture bounding lid of pupariuni ; d., dorsal ; d. I., dorso- 

 lateral ; /., lateral ; v. L, ventro-lateral; v., ventral area of 2nd abdominal 

 segment. Size of lateral spiracles is exaggerated. 



2. H. bovis. Diagram of tracheal system. Lateral view. 



x o 



3. The same. Ventral view. j 



I— III, segments of thorax ; 1-8. segments of abdomen. 



a. s., anterior spiracles: /. s., 1-6, lateral spiracles; p. s., posterior 

 spiracles ; long., longitudinal tracheal trunks ; a. c, 1-3, anterior 

 connectives; p. c, posterior connective; d. int. tr., dorsal internal 

 tracheae ; dig. tr., tracheae to digestive tube (numbers refer to the 

 abdominal segments ; note the sac-like swelling of dig. tr. 4) ; 

 I. tr., outer lateral tracheae ; sp. tr., spiracular tracheae (solidified). 



Plate IX. 



4. H. bovis. Fourth-stage larva, I— VI. The six lateral spiracles on the 



right side as seen in surface view, x 500. 



5. Left posterior lateral spiracle, surface view, x 500. 



sp. c, spiracular cavity : c. r., chitinous ridge. 



6. Left posterior lateral spiracle as viewed from within, x 500. 



m., markings around cavity (seen through secondary cuticle) ; 

 c. ?'., chitinous ridge formed by inturned scale-like area of primary 

 cuticle ; ct., vestigial spiracular trachea, solidified as chitinous plug. 



Plate X. 



7. Lateral spiracle in tangeutial section. 



8. The same, deeper in the body-wall. x 700. 

 P. The same, showing closure of cavity. ' 



10. Solidified spiracular trachea in cross-section, x 500. 



11. Transverse section of body-wall, showing lateral spiracle (/. s.) and 



its trachea, x 80, 



ct., outer, and ct. 1, inner, layer of primary cuticle ; ct. 2. secoiidai v 

 cuticle ; gr. granules in same ; ep. (figs. 10. 11). epidermis. 



