The butterfly fauna is rich in MSNP. Mycalesis oculus, Parantica nilgiriensis, Tirumala limniace, Tirumala septentrionis, Neptis hylas, Vanessa indica (Nymphalidae); Acytolepis puspa, Udara singalensis, Jamides bochus, Udara akasa (Lycaenidae); Eurema blanda, Eurema hecabe and Pieris canidia (Pieridae) are ubiquitous and Mycalesis oculus, Vanessa indica and Pieris canidia are abundant.
The butterfly fauna of the Park contain elements from three major biogeographical regions: the Oriental Region, Palaearctic and Afro tropical, of which majority of the species belonged to the Oriental region. The species Anaphaeis aurota, Catopsilia florella, Eurema briggita (Pieridae); Junonia orithya and Melenitis leda (Nymphalidae) are the afro-tropical elements and Cyrestis thyodamas and Vanessa indica (Nymphalidae) are the Palaearctic elements that are recorded from the study area. The danaid Danaus chrysippus representing both Afrotropical and Palaearctic region and Cynthia cardui (Nymphalidae), having worldwide distribution, are also recorded. Among these Mycalesis oculus, Vanessa indica and Pieris canidia are the most abundant species and are found to be characteristic of shola forests, not being represented frequently in other forest types in the Western Ghats. Cirrochroa thais (Nymphalidae) is the most abundant species in the Park followed by Vanessa indica, Mycalesis oculus and Zipoetis satis, Cirrochroa thais (Nymphalidae); Delias eucharis (Pieridea); Udara akasa (Lycaenidae) and Papilio polymnestor (Papilionidae) which are recorded from the study area are endemic to the Western Ghats, while the species Mycalesis oculus, Parantica nilgiriensis, Ypthima chenui, Ypthima ypthimoides (Nymphalidae) and Colias nilgiriensis (Pieridae) are endemic to the Western Ghats shared only with Sri Lanka. Similerly, Athyma nefte, Eriboea athamas, Libythea myrrha, Ypthima avanta, Ypthima ceylonica (Nymphalidae) and Colotis fausta (Pieridae) are commonly found in sholas of Munnar.
These shola forests are also peculiar in not harboring almost the entire aristolochian (troidine) guild, which include Troides minos, Pachliopta aristolochiae, P. hector (Papilionidae) etc. This guild is almost found in all other forest types of the Western Ghats. This is attributed to absence of species of the family Aristolochiacea in the area. The larvae of the members of the aristolochian guild are solely dependent on plants belonging to the family Aristolochiaceae and hence its diversity and abundance greatly influence the survival of the members of this guild. Apart from this, some of the other larger species like Papilio budha and Papilio paris are also completely absent.
Apart from the above, other insects found in the shola include beetles, bees, wasps, dragonflies as well as syrphid and tabanid flies which are abundant. The information on RET species in the Park is not fully available at present and needs further studies.