Caloptilia suberinella ( Tengström, 1848 )

Landry, Jean-François, Nazari, Vazrick, Dewaard, Jeremy R., Mutanen, Marko, Lopez-Vaamonde, Carlos, Huemer, Peter & Hebert, Paul D. N., 2013, Shared but overlooked: 30 species of Holarctic Microlepidoptera revealed by DNA barcodes and morphology, Zootaxa 3749 (1), pp. 1-93 : 17-18

6. Caloptilia suberinella ( Tengström, 1848) ( Gracillaridae : Gracillariinae )

Gracilaria suberinella Tengström, 1848: 145 . Type locality: Russia ( South Karelia).

BOLD:AAF8460

Palearctic distribution. Northern and Central Europe , Russia and China .

New North American records. Canada: British Columbia, Hazelton (in northwest central area of the province), 30 Jul 2009, 1 ♀ ( CNC) .

Diagnosis. The forewing ground colour is brown with dark brown and dirty white variegations. In North Europe, the forewing coloration varies from plain white or ochreous to plain black, but a majority of specimens have wings mottled with dark and light ( Mutanen & Välimäki 2012). In North America, it is quite similar to C. strictella (Walker) , both in colouration and in genitalia. In male genitalia, the saccus is very long, longer than the length of valvae, the valvae have the ventral margin medially bulged and distally sinuate, and the phallus has a row of short, stout, closely set spines extended over nearly its entire length, the spines being smaller in the distal section. In female genitalia, the distal two-thirds of the ductus bursae are smoothly sclerotized, without spinulations nor microsculpture, twisted at mid-length, the membranous anterior section is looped before entering the bursa; the inception of the ductus spermathecae is situated a short distance anterad of the ostium and has a short but distinctly sclerotized section that juts out of the ductus bursae; the sterigma is suboval.

The European populetorum (Zeller), also living on Betula spp. , closely resembles pale specimens of suberinella , but can be separated externally by the almost unicolorous pale tarsal segments in the fore- and mid-leg (dark and more clearly ringed in suberinella ). The male genitalia of populetorum differ by having a proportionally much shorter saccus, only a few cornuti in the phallus, and less elongated valvae. The female genitalia of populetorum differ in the smaller ostium, and weakly sclerotized and thinner ductus bursae ( Bengtsson & Johansson 2011). Caloptilia suberinella is obligatorily univoltine, whereas populetorum usually has a mid-summer generation in addition to the overwintering one.

Larval host. Birch, Betula spp. , according to Bengtsson & Johansson (2011) in open habitats, but actually preferring birches growing in mixed forests.

Note. This species is possibly native. If so, it is surprising that it has not been reported previously. Possibly it has been reported or recorded previously under the name C. strictella , to which it is very similar. The single Canadian specimen was collected in the interior of British Columbia, but the area is managed with tree plantations which include some non-indigenous species. Like many microlepidoptera , it is probably undercollected and may be more widely distributed than the single present record suggests. Because North American species of Caloptilia have never been the object of a taxonomic treatment, several existing names remain unrecognized or inadequately diagnosed. The majority of the species were described from Eastern North America, but many unnamed species are known from reared adults or larval shelters ( Powell & Opler 2009). There is a possibility that it is synonymous with C. strictella (Walker, 1864) : we failed to see significant differences between that Nearctic species and suberinella . However, the identification of strictella remains in doubt because the type has never been studied and the original description does not allow for clear placement, even at the family level. The species was originally described as a Gelechia and subsequently transferred to Caloptilia by Dyar (1903) without explanation. McDunnough (1946b) discussed the identity issue with strictella , and the identification of all subsequent specimens appears to have been based on his tentatively named material in the CNC. We did not pursue the investigation of the type of strictella , which is likely in the BMNH, because this would have entailed time and resources that were not available within the scope of the present work.