EXPLANATION OF PLATE I. 
The following letters always have the same signification : 
c, clypeus. m, mandibles. 
e, epipharynx. mp, maxillary palpi. 
hk, hypopharynx. mx, maxillae. 
z,  infraoesophageal ganglion. oe, oesophagus. 
2, labium. p, pharynx. 
76, labellae. pm, pm’, pharyngeal muscles. 
Zr, labrum. s, supraoesophageal ganglion. 
ly-e, labrum-epipharynx. tr, tracheal stem. 
The number of diameters enlargement is indicated against each figure. 
Shaded parts of sections are portions filled with connective tissue, nerves, air-spaces, 
and other parts, which have no significance in connection with points discussed in 
this paper. 
Fig. 1. Side view of head of Culex rufus, with extended mouth-parts; @, antennae. 
Fig. 2. Same from above with mouth-parts partly cut away. 
Fig. 3. Tip of labium of female Cu/ex. 
Fig. 4. Same of male Culew. 
Fig. 5. Tips of separated setae of mouth-parts of Culex. 
Fig. 6. Tip of labrum-epipharynx of Culex, seen from beneath and in section. 
Fig. 7. Cross-section through the labellae and tip of labium of female Cudex. 
Fig. 8. Cross-section near the middle of the proboscis of female Cu/ex. 
Fig. 9. Cross-section through pharyngeal region of the forward part of the head of 
female Culex. 
Fig. 10. Cross-section through the posterior part of the head of female Czex, to 
show the sucking bulb of the oesophagus. 46, lumen of the oesophageal bulb. 
bm, bm’, muscles to dilate the bulb. +, chitinous rods which support the oesophageal 
bulb. xm, retractor muscles of the maxillae, at the point of origin of their muscles. 
z, elastic plates of sides of bulb. 
Fig. 11. Longitudinal section of the head of female Culex. 6, oesophageal bulb. 
£, point where the clypeus appears nearly cut off from the rest of the head. v, valve 
between pharynx and oesophagus. 
Fig. 12. Cross-section near the middle of the proboscis of male Culex. 
Fig. 13. Cross-section at the base of the proboscis of male Culex. 
Fig. 14. Cross-section further into the base of the proboscis of male Culex. 
Fig. 15. Cross-section through the pharyngeal region of the head of male Cudex. 
