Trifurcula squamatella
Diagnosis. Externally most similar to T. immundella, but squamatella is usually distinctly larger (wingspan usually over 7.8 mm, in immundella less than 8.1 mm) and immundella has fewer than 44 antennal segments in ♂ or 40 in ♀. Fresh material can be separated by colour and also the broad male genitalia are conspicuous without dissection; the characteristic valval tips and gnathos can often be seen, simply by brushing away some scales. See also T. beirnei. Male genitalia can only be confused with those of beirnei, but the gnathos is a very good character. Female genitalia resemble T. beirnei, but differ (also from other Trifurcula species) by large number of setae and much smaller vestibulum.
Male. Wingspan: (6.6) 7.8-9.8 mm. Head: frontal tuft yellowish- white to yellowish orange; collar paler; scape white, sometimes with few brown scales; antenna with (42) 46-55 segments. Forewing rather narrow, uniform greyish brown irrorate, this colour being composed by three types of scales: white (almost transparent), with yellow tips and with grey-brown tips; these colours tend to fade in old material; forewing often paler along dorsum and costa; cilia-line irregular, terminal cilia yellowish white. Hindwing: light grey. Abdomen greyish brown, anal tufts yellow. Female. Wingspan: 8.4-10.0 mm. Antennae with 42-49 segments. Male genitalia. Very large, more than 0.5 mm long. Vinculum with comparatively short, rounded, ventral plate. Tegumen triangular. Uncus with medial projection terminally widened and bilobed. Gnathos very large, central element wide, with almost parallel margins, terminally rounded; anterior processes absent. Valva long, inner margin sinuate; ending in long narrow tip, which is curved inwards; transtilla with straight transverse bar. Aedeagus with three large cornuti, one long, straight, one long, curved and one short, curved, with large base. Female genitalia. T VIII laterally swollen, with more than 100 long setae on either side. Anal papillae each with about 60 setae. Hairy terminalia also visible without dissection. Bursa short, exceeding segment VII by half its length, covered with minute spines and pair of indistinct narrow signa, often with incomplete cells. Ductus spermathecae with 3 convolutions.
Immature stages unknown. The species has frequently been observed on Cytisus scoparius, which is almost certainly the hostplant.
Not found in Fennoscandia. Collected several times in WJ in Denmark. - In the Netherlands from three localities, further from southern England, southern Germany, France (van Nieukerken, 1987b) and Spain.
Voltinism: adults have been found throughout August and in September.
Description based on van Nieukerken and Johansson (1990)