Explanation of Plate II, 



1. Side view of head of Culex, with extended mouth -parts; a, antennae. 



2. Same from above with mouth-parts partly cut away. 



3. Tip of labium of female Culex. 



4. Tip of labium of male Culex. 



5. Tips of separated setae of mouth-parts of Culex. 



6. Tip of labrum-epipharynx seen from beneath and in section. 



7. Cross-section through labellae and tip of labium of female Culex. 



8. Cross-section near middle of the proboscis of female Culex. 



9. Cross-section through pharyngeal region of forward part of head of female Culex. 



10. Cross-section through posterior part of head of female Culex, to show the sucking 



bulb of the oesophagus. &, lumen of oesophageal bulb; bm and bm', muscles to 

 dilate the bulb; r, chitinous rods which support the oesophageal bulb; rm, 

 retractor muscles of maxillae, at their point of origin; t, elastic plates of sides 

 of bulb. 



11. Longitudinal section of head of a female Culex. 6, oesophageal bulb; g, point 



where the clypeus appears cut off from rest of head; v, valve between pharynx 

 and oesophagus. 



12. Cross-section near middle of the proboscis of a male Culex. 



13. Cross-section at base of the proboscis of a male Culex. 



14. Cross-section further into the base of the proboscis of a male Culex. 



15. Cross-section through pharyngeal region of head of a male Culex. 



Tbe following letters have the same signification tliroughout : 



c, clypeus. Ir, labrum. p, pharynx. 



e, epipharynx. h-e, labrum-epipharynx. pm, pm', pharyngeal muscles. 



h, hypopharynx. m, mandibles. s, supracesophageal ganglion. 



♦, infracesophageal ganglion. mp, maxillary palpi. tr, tracheal stem. 



I, labium. mx, maxillae. 



n, labellae. oe, oesophagus. 



36b 



