Feminine, but usages exist that assume without explanation that
Phylo is masculine. Most likely named after Phylo, a classical Greece female name in Homer. There are no male personal name usages to be found from that period that are transliterated as 'Phylo'. There are several classical Greece female names ending in 'o' rather than the more usual 'a'. Thus there is no reason considering the word alone as a personal name to think
Phylo is other than feminine. The secondary way to decide a genus gender is to examine the epithet combined with it. Kinberg combined
Phylo with the adjective (or rarely a noun) felix, which means happy or fortunate (for instance Arabia felix was a term used for the flourishing fertile part of Arabia, now Yemen), and as an adjective has the same ending whether masculine or feminine. While Felix as a noun is a masculine given name used from Roman times, Kinberg would not have used the word as a noun resulting in two personal name nouns together without any logical reason for the choice. However, the presence of the word felix may have wrongly suggested masculinity for the genus gender to later workers such as Hartman, as they were most familiar with Felix used as a male name (the popular cartoon character from the 1920s 'Felix the cat' was male!). Alternatively there may have been a belief female Greek names could not end in 'o' (they can). There are no other contemporary 19thC authors who created original names in
Phylo that can be used as guidance, but some older recombinations come from the feminine genera
Aricia and
Orbinia where they had appropriate feminine endings, but Hartman (1957) changed them to masculine in
Phylo.