Diagnosis. Resembles E. quinquella and E. coscoja, which both have a similar pattern of three spots, but the spots are usually less distinct in algeriensis. E. coscoja is separated by the pale head, and E. quinquella by the partially black thorax (anterior part), which is completely white in algeriensis, and the yellow hairpencil in quinquella, versus the white one in algeriensis. E. algeriensis has also many more antennal segments than the other two species.
Redescription. Male. Forewing length 2.4–2.9 mm, wingspan 5.3–5.7 mm. Head: frontal tuft almost black, collar slightly paler; scape white; antenna brown, with 48–54 segments. Thorax and tegulae completely white. Forewing brown, with pattern of two to three indistinct white spots, one at 1/3 at costa, one at dorsal margin slightly beyond middle and the third at 2/3 in disc, usually not touching costa, often reduced or almost absent; sometimes a small indistinct basal spot present; cilia-line distinct; cilia silvery white; underside light brown-grey. Hindwing and cilia dark grey; a white hairpencil, surrounded by yellow scales. Abdomen grey, with white anal tufts.
Female. Forewing length 2.1–2.6 mm, wingspan 4.9–5.6 mm; antenna with 27–35 segments. Hairpencil absent, further as male.
Male genitalia. Capsule 245–260 μm long. Tegumen rounded. Gnathos with central element divided, distal part prominent, broadly spatulate, basal part with serrate margins. Valva length 195–215 μm, inner margin concave, tip wide, strongly curved inwards and truncate, dorsal surface with few setae; sublateral processes about 1/3 length of transverse bar of transtilla. Aedeagus 250–275 μm, carinae pointed, single, bi- or trifurcate.
Female genitalia. T8 (and T7?) with more than 70 long setae, partly in row along anterior margin, no scales. Anal papillae with 24–28 setae. Vestibulum with vaginal sclerite, a prominent dorsal spiculate pouch, and a group of densely packed pectinations near entrance of ductus spermathecae. Corpus bursae 605–660 μm without pectinations; signa dissimilar, longest 386–450 μm (2), shortest 355–420 μm, 3.5–3.9× as long as wide (2). Ductus spermathecae with 2 indistinct convolutions.
Hostplants. Evergreen oaks Quercus rotundifolia Lam., Q. ilex L., Q. suber L. (Van Nieukerken 1985; Nieukerken et al. 2006).
Leafmine. Egg on leaf upperside. Mine a highly contorted gallery, often following veins partially, filled with black frass. Not separable from other gallery mines of E. haraldi, ilicis or heringella.
Larva. According to original description the larva is green. However, while collecting the French material, EJvN did not note any green colour and larvae were tentatively identified as ilicis/haraldi. Since the latter have normally whitish larvae, the original description is probably incorrect, or refers to the colour as appearing inside the mine. No ventral plates have been observed.
France, Mediterranean area: Van Nieukerken et al. 2006. Otherwise only known from the Atlas mountains in Algeria and Morocco.
Life history. Probably univoltine, adults on the wing in June and July, larvae found in February-March in France, April in Algeria (high mountains).
This taxonomic description is based on Van Nieukerken (1985) and Van Nieukerken et al (2010).