EXPLANATION OF PLATES 



Plate i 



1. Periplancta americana L., Orthoptera, sagittal section of head slightly 



to the left of median plane. 

 lA. Same, diagrammatic detail of the relation of the dorsal dilator muscle 

 of the cibarium, 8, to the dorsal muscle of the labrum, 4. 



2. Same, dorsal view of head with part of head wall removed to expose 



muscles. 



3. Same, ventral view of labium and posterior head region with part of 



integument removed to expose muscles. 

 3A. Same, diagrammatic detail of relationship of the muscles of the labial 

 palpus, 25, 26, and 2j. 



Plate 2 



4. Anisolabis maritima Gene, Dermaptera, dorsal view of head with part 



of head wall removed to expose muscles. 



5. Same, sagittal section of head slightly to the left of median plane. 



6. Same, ventral view of head with part of integument removed to expose 



muscles. 



7. Corydahis corniitus L., Neuroptera (adult), dorsal view of part of head 



with integument removed to expose muscles. 



8. Same, sagittal section of head slightly to the left of median plane. 



9. Same, ventral view of head with part of integument removed to expose 



muscles. 



Plate 3 



ID. Corydahis cornutiis L., Neuroptera (larva), dorsal view of head with 

 part of integument removed to expose muscles. 



11. Same, ventral view of head with part of integument removed to expose 



muscles. 



12. Same, sagittal view of head slightly to the left of median plane. 



13. Spheciiis speciosus (Dru.), Hymenoptera (adult), lateral view of labium 



with part of integument removed to expose muscles and also portion 

 of anterior tentorial arm with points of muscle origin. 



14. Same, sagittal section of anterior (dorsal) head region slightly to the 



left of the median plane. 



15. Same, dorsal view of anterior region of head with part of integument 



removed to expose muscles. 



16. Same, ventral view of labium and tentorium with part of integument 



removed to expose muscles. 



Plate 4 



17. Harpalus calig'mosus P., Carabidae (adult), dorsal view of head with 



part of integument removed to expose muscles. 



18. Same, ventral view of labium with part of integument removed to expose 



muscles. 



37 



