Plebejus trappi ¦ Alpine Zephyr Blue ¦ euroButterflies

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Plebejus trappi

Alpine Zephyr Blue

euroButterflies

by Matt Rowlings

Valais, Switzerland, July 2021

Valais, Switzerland, July 2021

Field notes and information

This is the zephyr blue from the Alps. It's somewhat larger than the other taxon in the group.

Identification & Similar species: Separated from other zephyr blues by distribution. And from other Plebejus sp by the absence of bright reflective blue scales in the underside hindwing marginal spots.

Resembles the Escher's blue, A. escheri, which is little brighter and less violet in colour on the male upperside and on the underside there is a strong single white chevron originating from the submarginal orange spots, past the post discal spots and towards the discal spot. The current species has a series of small white chevrons radiating inwards from each of the orange submaringal spots, culminating to a point at the post discal spots but not passing them.

Distribution & Flight: Western Alps, principally south Switzerland, but also northwest Italy and one or two records from France. Flies end May/ June, possibly into July in later seasons.

Habitat & Behaviour: It is found in very small colonies where it is common. The colonies appear to be confined by the extent of the foodplant, a very hairy low growing stemless milk vetch, Astragalus exscapus which has yellow flowers at its centre at ground level.