64 ILLINOIS BIOLOGICAL MONOGRAPHS [234 



EXPLANATION OF PLATE 

 •Cephalic Aspect of the Head and Mouth-pabts 



Fig. I. Hypothetical head. 



Fig. 2. Simulium venustuni, female. 



Fig. 3. Simulium johannseni, male. 



Fig. 4. Bibiocephala elegantula, male. 



Fig. 5. Bibiocephala elegantula, female. 



Fig. 6. Rhabdophaga strobiloides. 



Fig. 7. Mycetobia divergens. 



Fig. 8. Psychoda albipennis. 



Fig. 9. Rhyphus punctatus. 



Fig. 10. Psorophora ciliata, female. 



Fig. II. Mycetophila punctata, female. 



Fig. 12. Chironomus ferrugineovittatus, female. 



Fig. 13. Bibio femoratus, male. 



Fig. 14. Bibio femoratus, female. 



Fig. 15. Ptychopiera rufocincta. 



Fig. 16. Trichocera bimacula. 



Fig. 17. Sciara varians. 



Fig. 18. Tipula bicomis. 



