|
Z.griseana
|
Z.rufimitrana
|
Z.ratzeburgiana
|
Z.isertana
|
|
|
|
These four species have a similar external appearance. Z.rufimitrana is rare - the distribution map in Sterling & Parsons includes SW England, most of the south coast of England, parts of Norfolk and Suffolk and patchily further north. Hants Moths reports 2-3 records per decade and Norfolk Moths states that it has not been recorded in Norfolk since 1960. There are no images of this species obtained in Britain on a Google search.
Generally, the four species can be segregated into two groups of two based on size. In view of the rarity of Z.rufimitrana, specimens with a forewing length <7.0mm will usually be Z.ratzeburgiana. Habitat may help distinguish the two larger species (see table below). Well-marked specimens of Z.isertana may be distinguished by the comparatively small and usually trapezoidal blotch of (pale) ground colour on the dorsum of the forewing, in Z.griseana this is relatively large, usually triangular or subquadrate and almost invariably reaches the costa; however, both species are variable and there are many examples of Z.isertana in which the median dorsal blotch is obscured.
Generally, the four species can be segregated into two groups of two based on size. In view of the rarity of Z.rufimitrana, specimens with a forewing length <7.0mm will usually be Z.ratzeburgiana. Habitat may help distinguish the two larger species (see table below). Well-marked specimens of Z.isertana may be distinguished by the comparatively small and usually trapezoidal blotch of (pale) ground colour on the dorsum of the forewing, in Z.griseana this is relatively large, usually triangular or subquadrate and almost invariably reaches the costa; however, both species are variable and there are many examples of Z.isertana in which the median dorsal blotch is obscured.
Z.griseana |
Z.rufimitrana |
Z.ratzeburgiana |
Z.isertana |
|
Size: fw (S&P) mm |
7.5-10.5 |
5.5-7.5 |
5.5-7.0 |
7.0-9.5 |
Size: ws (BTM) mm |
16-22 |
12-15 |
14-19 |
|
Size (my specimens) |
8.0-9.1 (7) |
6.3-6.5 (3) |
6.5-8.7 (7) |
|
Status |
local throughout GB |
rare, mainly SW England |
local throughout GB |
common throughout GB |
Habitat |
coniferous woodland, parks, gardens |
conifer plantations |
coniferous woodland, parks, gardens |
oak woodland |
Larval foodplants |
Sitka Spruce, Larch, Pine |
Silver/Grecian Fir, Stone Pine |
Spruces |
Oaks |
|
|
Male genitalia: Zeiraphera species have a "shouldered" tegumen with a small uncus, prominent drooping socii, the costa (dorsal margin) of the valva shows a small prominence medially and the ventral border shows an indentation at the junction of sacculus and valvula. Z.isertana has a narrow valva only slightly broader at the base than at the apex, its ventral border is shallowly concave subapically; and the medial costal prominence is more well-marked than in the other species. Z.griseana has a more angular sacculus and a deeper indentation at the junction of the sacculus with the valvula than in the other species; the ventral border of the valvula is smoothly convex and the valvula is much broader at its base than at its apex. Z.ratzburgiana has a very shallow indentation at the junction of sacculus and valvula, the ventral margin of the valvula is very convex at ~junction of proximal 1/3 with distal 2/3, the valvula is broad and narrows relatively little in apical third, and the medial costal prominence is minimal. Z.rufimitrana is not shown at Moth Dissection; the drawings in Pierce and Metclafe suggest a relatively short broad valva. The discreteness of the uncus also varies between the species, being less discrete/more shallow-seded in Z.griseana than in in Z.ratzeburgiana or Z.isertana.
P&M also describes differences in the number of cornuti: ~50 for Z.griseana, ~13 for Z.ratzeburgiana, ~21 for Z.rufimitrana and ~15 for Z.isertana.
Summary:
Z.griseana - valva broad, tapering; sacculus angular; uncus not clearly discrete from tegumen
Z.rufimitrana - valva broad, short
Z.ratzburgiana - valva broad, convexity of valva more prominent than concavity of sacculus/valvula junction; uncus a discrete central prominence
Z.isertana - valva narrow, ventral border concave subapically, medial costal prominence strong; uncus a discrete central prominence
P&M also describes differences in the number of cornuti: ~50 for Z.griseana, ~13 for Z.ratzeburgiana, ~21 for Z.rufimitrana and ~15 for Z.isertana.
Summary:
Z.griseana - valva broad, tapering; sacculus angular; uncus not clearly discrete from tegumen
Z.rufimitrana - valva broad, short
Z.ratzburgiana - valva broad, convexity of valva more prominent than concavity of sacculus/valvula junction; uncus a discrete central prominence
Z.isertana - valva narrow, ventral border concave subapically, medial costal prominence strong; uncus a discrete central prominence
|
|
|
|
|
|
Female genitalia: Zeiraphera species have an elongate ovipositor and the sterigma (connecting the anterior apophyses) has an emarginate anterior border. The number and size of the signa and the shape of the sterigma provide distinctions between the species. All except Z.rufimitrana are shown at Moth Dissection. All 4 species are illustrated in Pierce & Metcalfe who also provide a limited description. Z.griseana has a single signum, Z.rufimitrana has one standard horn-like signum and one small scobinate plate, both Z.ratzeburgiana and Z.isertana have 2 horn-like signa. P&M describe the sterigma as "long emarginate" in Z.ratzeburgiana and Z.griseana, "long deeply emarginate" in Z.rufimitrana and "slightly emarginate" in Z.isertana. This is not a particularly helpful description in respect of Z.isertana - in which the plate connecting the apophysis anteriores is strongly sclerotised with both anterior and posterior borders emarginate in the shape of a bow-tie.
Summary:
Z.griseana - Single horn-like signum
Z.rufimitrana - Single horn-like signum and a small scobinate plate
Z.ratzburgiana - 2 horn-like signa; plate connecting anterior apophysis with a deeply emarginate anterior border and a diffuse posterior margin
Z.isertana - 2 horn-like signa; plate connecting anterior apophysis bow-tie shaped
Summary:
Z.griseana - Single horn-like signum
Z.rufimitrana - Single horn-like signum and a small scobinate plate
Z.ratzburgiana - 2 horn-like signa; plate connecting anterior apophysis with a deeply emarginate anterior border and a diffuse posterior margin
Z.isertana - 2 horn-like signa; plate connecting anterior apophysis bow-tie shaped
|
|
|
|
|
|
