73.023 Plusia putnami (Lempke's Gold Spot)
fw: 14-15mm (waring & Townsend), ws 34-36mm (MBGBI10); Jul-Aug; wood/purple small-reed (Calamagrostis epigejos/canescens); local in fens, marshes and other open damp places in East Anglia, N.England & S.Scotland, very local elsewhere in in S.England and Wales
ID: Forewing orange-brown with 2 prominent central white spots and a series of 4 apical streaks. P.festucae (Gold Spot) is very similar – differences are as follows: 1) the more distal white spot is elliptical or tear-shaped in P.festucae, round in P.putnami; 2) the most dorsal of the 4 apical streaks is white in both species, but in P.festucae the proximal end of this streak is angular and comes to a point at its dorsal edge, while in P.putnami the proximal end of the streak is blunt (the postmedian line usually delineates the proximal margin of this streak such that it form a very acute angle in P.festucae and a very obtuse angle in P.putnami) ; 3) the subterminal line is often indistinct in P.festucae, more distinct in P.putnami; 4) larger individuals should be P.festucae as the forewing length range for P.festucae is 14-19mm. MBGBI10 states that genital dissection is needed to determine the species with confidence.
Male genitalia: In the aedeagus the single cornutus is much more elongate in P.festucae than it is in P.putnami (length 8x width vs 4x). There are are 2 processes from the sacculus in both species, one near the base (clavus) and one more distally (clasper). In P.festucae the clasper is very slender and shorter than the clavus, which is clubbed; in P.putnami the clasper is broader and stronger and longer than the clavus which is hardly clubbed (despite clavus meaning 'club'!).
Male genitalia: In the aedeagus the single cornutus is much more elongate in P.festucae than it is in P.putnami (length 8x width vs 4x). There are are 2 processes from the sacculus in both species, one near the base (clavus) and one more distally (clasper). In P.festucae the clasper is very slender and shorter than the clavus, which is clubbed; in P.putnami the clasper is broader and stronger and longer than the clavus which is hardly clubbed (despite clavus meaning 'club'!).
Dissection
Male genitalia
§1 Strumpshaw Fen, Norfolk; 10/07/2015; male; fw 15.9mm; to light
§2 Sutton Fen. Norfolk; 17/07/2017; male; fw 14.2mm; to light
All images © Chris Lewis
§2 Sutton Fen. Norfolk; 17/07/2017; male; fw 14.2mm; to light
All images © Chris Lewis
Page published 30/12/2015 (§1) | §2 added 17/04/2018