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Species
Cameraria ohridella Deschka & Dimic
IUCN
NCBI
EOL Text
Adults are small, 3-4 mm. forewing length and 7-9.5 mm. wingspan. Larvae are also small, up to 5.5 mm. in length.
Like at least one other species of Cameraria, the female of C. ohridella is an indiscriminate egg layer (Béguinot, 2009). A range of 20-82 eggs are recorded to be laid (in captivity) (Šefrová, 2001; Girardoz et al., 2006) on the leaf upper surface, which hatch in 4-21 days (Šefrová, 2001; Pschorn-Walcher, 1994). The larva on hatching from the egg (Fig. 12), develops a gallery mine on the upper surface of the leaf, and sap-feeding early instars are flattened in shape for such a lifestyle and legless with forward oriented mandibles (Fig. 10). The larva has four feeding instars, occasionally a fifth, developing in 20-45 days depending on season and climate, and two non-feeding, spinning stages (Figs 13, 14), one outside the cocoon and one within, although a cocoon is optional for earlier generations (Šefrová, 2001; Pschorn-Walcher, 1994; Freise, 2001). The cylindrical, normally 4th instar, larva enlarges the originally circular, reddish-brown mine along the main veins of the leaf during which time it is adapted to eat the palisade tissue of the parenchyma, damaging a surface of 4-7 square centimetres. In the absence of effective environmental controls and starting their development with a long sap-feeding period, larvae appear highly adapted to overcome any defenses of the hostplant leaves (Béguinot, 2009). The pupa stage lasts for 12-20 days during summer generations (Šefrová, 2001). Pupation of late summer generations always occurs in a round cocoon, and the moth hibernates during the winter in the pupal stage. The adult lives for a few days, and although they have a developed proboscis, but there seem to be no published observations of their feed as an adult. Adults flight peaks are in May (20th April - early June), July (20th June - early August) and August/September (10th August - 15th September), with some adults appearing up to early October (Šefrova and Laštůvká, 2001).The total life cycle lasts 6-11 weeks in summer generation. An increasing proportion (up to 90%) of each generation goes into to diapause, which can last up to two or three years (Šefrová, 2001).
The species is not generally considered to need conservation management except for its control. However, the discovery of unique, not yet invasive haplotypes in remote parts of the Balkans (Valade et al., 2009) might alter this viewpoint. In fact also the hostplant is red-listed in Albania (see under Threats). Most mitochondrial races in the Balkans appear to be narrowly endemic including in Albania. The today dominant (and perhaps more invasive) haplotype A may already have been swamping some natural populations, for example in Karitsa, Ossa Mountain, E. Greece. Haplotype frequency changes in the population at Karitsa, evidenced by a series of herbarium samples from 1936 to 1981, seem to have been caused by vehicular transport of the moth (Gilbert et al. 2004) aided by late road development in the Balkans (Lees et al. 2011). It is noteworthy that some hard of access sites, such as Perivoli in Greece, contain populations with remarkable genetic diversity: Valade et al. (2009) reported 11 mitochondrial haplotypes from Perivoli.
Small moth (Figs 3, 4), adults around 3.5 mm in forewing length, forewings background colour orange-brown with basal white longitudinal streak and white v-marks bent towards costa and running straight across dorsum at rest, edged posteriorly in black, two of these fasciae continuous medially, one post-medial fascia interrupted and a final convex fascia towards wing apex, bisected by a diffuse blackish subapical streak. Fringe forming a conspicuous orange tuft that is longest dorsally at rest (Fig. 1). Head tufted with orange hair-like scales intermixed with white, scape and base of antenna silvery white. Antennae about 4/5 forewing length. Fore and mid-legs equally banded white and black, hindleg with relatively more white.
Valade et al. (2009) have identified 25 geographically structured haplotypes, based on analysis of the mitochondrial DNA of 486 individuals from 88 localities. In addition, they have showed that there is significantly higher mitochondrial haplotype diversity in the probable region of origin, the southern Balkans, than in central and western Europe (Valade et al., 2009).
The moth has no positive economic value but is a dramatic,perhaps iconic example of the spread of an invasive species in Europe and the risks associated with increases in human transport and activity including the use of amenity trees. Cameraria ohridella has also been flagged as a case study of the importance of herbaria to the study of insect plant interactions and origins of invasive species and diseases, since (despite decades of debate on the moth's origins) this important potential source of historical biodiversity information has generally been overlooked (Lees et al. 2011).
The mine (Fig. 2) is not easily confused with that for any other insect species as no other Cameraria recorded in Europe and no other leaf miners on horsechestnut. The fungal pathogen Guignardia aesculus also causes brown patches that could be confused with Cameraria mines, but more uniformly brown. Mines of Cameraria aesculisella in USA are of similar appearance to those of C. ohridella, but the species does not appear closely related. The adults resemble closely some species of Phyllonorycter, from which larvae may be distinguished by reduced legs and pupae by the absence of cremastral hooks, and the presence of strong spinoid setae in the 1st to 5th abdominal segments (de Prins et al., 2003).
No paper has yet been focused on the phylogenetics of the genus Cameraria.
As an invasive species, the moth is a grave risk to planted horse chestnut trees and may also pose a risk to sycamores Acer pseudoplatanus and A. platanoides, due to increased attacks in some parts of Europe. This aspect has recently been investigated (Péré et al., 2010). If the insect arrives in North America or the Far East, it could also threaten some Aesculus or possibly Acer species there on which it can complete development, both of which genera have a community of native gracillariid-leaf miners and their parasitoids.
Parks and urban areas where horse-chestnut planted, generally avoiding trees planted close to the sea, and within natural stands in the Balkans (Valade et al., 2009). The moth prefers the shadier lower to mid-stratum of trees within parks tending to avoid the canopy (Syeryebryennikov, 2008). Horse-chestnut itself prefers moist, well drained soils and is thus not widely planted in North America owing to the possibility of leaf scorch. Natural stands of A. hippocastanum in the Balkans (Greece, Macedonia, Albania) are found in shady, humid ravines between 380-1330 m.(Avtzis et al., 2007; Lack, 2000), and this is presumably the natural habitat of the moth.