Cosmopterix

Descriptive terminology for head, thorax and forewing

Wingvenation of Cosmopteryx lienigiella

Cosmopterix species are very small to small moths with a forewing length of 2.9-6.5 mm. Head smooth-scaled, rather long and narrow caused by the large and bent scales on the vertex; frons distinctly lighter than vertex, from vertex to neck tufts often a median and/or two lateral white lines; antenna three-quarters to four-fifths of the length of forewing, often slightly serrate distally, and generally with a white, often partly interrupted, anterior line and several white sections in the apical part; labial palpus cylindrical, porrect, apical segment strongly angled upwards and often reaching well above the head. Thorax with or without a median white line, tegulae often lined white inwardly. Forewing narrowly lanceolate with long and very narrowly protruding apex and usually with a very characteristic yellow or orange fascia beyond the middle, this fascia bordered by tubercular metallic fasciae or spots; basal area with a metallic fascia or spots or with three to six longitudinal lines of different length, cilia concolorous around apex, paler towards dorsum. Hindwing almost linear, less than half the width of forewing and acutely pointed, from pale yellow to dark grey, without markings, cilia concolorous without ciliary lines. The forewing can generally be divided into three parts: The basal area from base to middle of wing, followed by the broad transverse fascia and beyond this the apical area. The basal area generally with a series of longitudinal lines, often very narrow or a single and oblique, sometimes interrupted, fascia. The lines are mentioned from costa to dorsum as the costal, the subcostal, the medial, the subdorsal and the dorsal line. The transverse fascia is strikingly coloured from pale yellow to orange and in combination with the narrow wings it makes the species of Cosmopterix and Pebobs easy recognisable. The transverse fascia is always more or less edged on both sides by fasciae or spots. These fascia or spots consist of very strikingly silver or golden metallic coloured tubercular scales. Some species partly or completely lack the yellowish colour of the transverse fascia. However, the presence of the ‘fascia’ can be observed by the lining tubercular fasciae or spots. The transverse fascia can be edged by a combination of inner and outer fasciae and/or by an inner and outer (sub)costal and (sub)dorsal spots. Sometimes the (sub)costal and (sub)dorsal spots are situated inside the transverse fascia. The apical area is generally concolorous with the basal area, but occasionally the colouration differs. In the centre or on the dorsal side of the apical area is a longitudinal apical line, running from the transverse fascia to apex of forewing. This line is often interrupted or only present as one or more dots or streaks. Markings of the costal and dorsal cilia of the forewing are as follows: a white streak from outer costal spot in almost all of the species, a white streak or spot connected to the apical line is very common, and occasionally there is a white streak from outer dorsal spot. For identification of the species by the external features, mainly the markings of the head, thorax and forewing are of diagnostic importance. Wing venation with 12 veins in forewing and 7 veins in hindwing. Forewing with Sc and R1-R4 to costa; R5 directing towards the narrow tip; M1-CuA2 to termen; CuP very weak and not reaching termen; 1A+2A with basal fork, to dorsum. Hindwing Sc and Rs to costa; M1-CuA2 to termen; veins often not fully developed due to the narrow shape of the hindwing.[2]

The larvae are leaf miners on a large diversity of usually herbaceous plants. They have been found oligophagous or even monophagous on the following plant families: Asteraceae, Cannabaceae, Convolvulaceae, Cyperaceae, Poaceae, Fabaceae, Urticaceae. The mines are blotch mines and in several species the larvae more or less frequently change mines. Larvae of other species stay in a single mine during their complete development and leave the mine only prior to pupation or pupate inside the mine. In several species the larva constructs a silken tunnel inside the mine in which it hides when not feeding or when disturbed. In colder climates species usually have one generation where hibernation takes place in the larval stage in a cocoon in or outside the mine. Pupation takes place in spring. In warmer climates the species have more than one, sometimes overlapping, generations.

For Cosmopterix gomezpompai a twirling behaviour has been observed by the adult. In this case the moth runs on the upper side of a leaf and simultaneously makes very fast circling movements. As soon as it comes across something unusual on the surface, like a spot, the circling slows down and is concentrated on that spot. It appears that it is feeding mostly on the dark brown spots (most likely a part of a bird dropping) on the leaf. Probably the moth is looking for nutrition. The twirling behaviour, without the possible feeding, has also been observed with Cosmopterix pulchrimella in Greece. This behaviour is described for Cosmopterix victor and also for a species of the family Gelechiidae.