In northern Europe at least, O. obscuratus is usually readily recognisable as it is the only frequently encountered species which has copious yellow or creamy markings.However, there are 2 pitfalls:

1. Similar appearance of Ophion forticornis
2. Dwarf forms of O. obscuratus that can superficially resemble other Ophion species

Distinguishing O. forticornis from O. obscuratus
O. forticornis:

• is rarely collected in Britain (but is seemingly more frequent in some other countries)
• is restricted to sand dunes
• has a much greater gap between the ocelli and eyes
• has a rather slenderer metasoma (abdomen)

Dwarf forms of O. obscuratus
O. obscuratus is known to occur in 3 distinct morphs in Britain (Brock, 1982):

• spring form
• 'autumnal dwarfs'
• 'autumnal giants' – the most frequent form

Whether they really belong to the same species is not certain.The spring and dwarf forms have been reared from a variety of low-feeding moth larvae of the family Noctuidae, such as Mythimna and Lycophotia. The autumn (and winter) flying giants, have never been reared. The host must almost certainly be a very common, yet hardly reared noctuid larva.Dwarf forms of O. obscuratus that lack the yellow markings superficially resemble other Ophion species, such as:

• O. crassicornis
• O. parvulus

However, they can still be recognised as O. obscuratus by the:

• yellow apex to the stigma
• the noticeably paler stripes along the inner edges of the eyes