Difficult Phyllonorycter species
Making a reliable key to distinguish Phyllonorycter maestingella, esperella, dubitella, coryli, cerasicolella and spinicolella on external features has proved to be problematic. All of this group have a ground colour which is somewhat variable between orange and brown; 4 costal and 3 dorsal white strigulae; C1 and D1 not meeting to form a complete fascia and forming an acute angle with each other; a white line at the lateral margins of the thorax (and /or dorsal margin of the tegulae) "continuous with" a basal white streak extending at least to the dorsal origin of D1 and usually to ~half-way along D1; a white median thoracic line “continuous with” a white dorsal streak of variable extent; a black apical streak of variable extent and a largely pale antenna, the terminal segment or two commonly dark. There is intra-specific variation in ground colour, extent and boldness of black edging to the strigulae and basal streak, extent and boldness of the apical streak and extent of the dorsal streak - and further variation occurs with wear.
P.esperella (labelled image below) is nearly always noticeably orange and may be distinct in having C1 extending proximally for a short distance along the costa. It also has a contrastingly white caudal tuft at the apex of the abdomen and this may help distinguish it from P.maestingella, at least, in which the dorsal portion of the caudal tuft is brownish-fuscous
P.maestingella may also be distinct in having a relatively short basal streak, usually reaching to but not much beyond the dorsal origin of D1.
However, for now, I regard the whole of this group as requiring genital determination.
P.esperella (labelled image below) is nearly always noticeably orange and may be distinct in having C1 extending proximally for a short distance along the costa. It also has a contrastingly white caudal tuft at the apex of the abdomen and this may help distinguish it from P.maestingella, at least, in which the dorsal portion of the caudal tuft is brownish-fuscous
P.maestingella may also be distinct in having a relatively short basal streak, usually reaching to but not much beyond the dorsal origin of D1.
However, for now, I regard the whole of this group as requiring genital determination.
Male genitalia
The general arrangement of Phyllonorycter male genitalia is illustrated above (P.maestingella). The main features useful in identification are the costae and costal spines and the valvae and valval spines. These features are often asymmetrical, but within the group under consideration only P.dubitella has distinctly asymmetrical valvae; all the other species have more-or-less symmetrical valvae, costae and costal spines. In the table below a spine is long if it is clearly longer than the costa it arises from and short if it is about the same length as the costa. P.coryli is distinct in having both short costal spines and short valvae, so that the costal spine extends as far as the apex of the valva. P.esperella is the only remaining species in which the costal spine is short and in this species the spine does not reach half-way to the valval apex. The remaining three species have long costal spines - in P.maestingella the spine does not quite extended as far as the valval apex while in P.cerasicolella and P.spinicolella the spine is very long, extending beyond the valva apex. These three species all have a subapical valval spine, but in P.maestingella this spine is very small. P.cerasicolella and P.spinicolella can be separated by the presence of prominent bristles along the ventral valval margin in P.cerasicolella, these being present to only a minimal extent in P.spinicolella.
The "saccus" of Phyllonorycter does not seem to be homologous with the saccus of other Lepidoptera. In most Lepidoptera the saccus is clearly part of, or an extension from, the vinculum; in Phyllonorycter it is easily detached and may actually be integumentary in origin (derived from ventral plate of S8?).
The "saccus" of Phyllonorycter does not seem to be homologous with the saccus of other Lepidoptera. In most Lepidoptera the saccus is clearly part of, or an extension from, the vinculum; in Phyllonorycter it is easily detached and may actually be integumentary in origin (derived from ventral plate of S8?).
costae |
valvae |
|
P.maestingella |
spines long |
small subapical spine |
P.esperella |
spines short |
much longer than costae + spine |
P.dubitella |
? |
asymmetrial, left with a long curved apical spine |
P.coryli |
spines short |
short, about as long as costae + spine |
P.cerasicolella |
very short with a very long spine |
subapical spine, prominent marginal bristles |
P.spinicolella |
very short with a very long spine |
subapical spine, few marginal bristles |
Phyllonorycter genitalia are very fiddly to prepare - I await better material before these differences will be illustrated here.
Female genitalia
Four of these species have a strongly sclerotised antrum (P.esperella, P.coryli, P.spinicolella and P.cerasicolella), the sclerotisation continuous with a line of sclerotisation along the antiorior margin of A8 and extending into the anterior apophyses. It would seem from MBGBI2 and Moth Dissection that the usual way of separating these species is by comparing the level of the anterior end of this sclerotisation with the anterior margin of the 7th abdominal segment - well short of the margin in P.esperella, just short of the margin in P.spinicolella, just beyond the margin in P.cerasicolella and well beyond the margin in P.coryli. *
P.maestingella has a sclerotised antrum that is short (extending about ½ the length of A7) and not continuous with the anterior margin of A8. P.dubitella has a small sclerotised ostial plate with a shallowly emarginate posterior border. The signum of all these species seems quite similar. * I am wondering if comparing the length of the introitus with the length of an anterior apophysis would be (more) reliable.
Ratios from my material and from images at Moth Dissection are shown in the table below. More work needed.
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Page published 27/02/2020