Phytomyza ilicis Curtis, 1846
The present species is closely related to Phytomyza ilicicola and other species mining on Ilex leaves. It is both the only species of this group being native of Europe and the only European leaf miner on Ilex aquifolium.
IMPORTANT CHARACTERS
Adults
Wing length: 2.8 - 3.3 mm. The species is similar to the exclusively Nearctic Phytomyza ilicicola but larger. The mesonotum is less densely covered with pubescence than in ilicicola.
Male terminalia
Aedeagus similar as in Phytomyza ilicicola (Phy ilicis aedeagus.pct).
Immature stages
The larvae are rather large with strong mouthparts. Cephalopharyngeal skeleton as shown in picture (phy ilicis ceph.pct). Mandibles are strongly asymmetrical, in side view the smaller left mouth hooks are usually concealed by the larger right ones. Larva with frontal process just above the facial mask, the locomotion welts are rather fine.
Anterior spiracles are elongated and unbranched at tip. Posterior spiracles with numerous spiracular bulbs not organized in a circle or semicircle.
BIONOMICS
Miall and Taylor, 1907 were the first to study the biology of Ph. ilicis. Simultaneously, their paper was a pioneer work on larval morphology of Agromyzidae. A further contribution about Ph. ilicis is Cameron, 1940.
As the related species Phytomyza ilicicola, the species treated here is strictly univoltine. In the spring fresh and soft leaves are used for oviposition. The eggs are placed into the midribs on the underside of the leaves. Mainly during the early autumn the young larva mines slowly through the midrib towards the tip of the leaf. The main larval development takes place in winter: After entering the leaf blade, an irregular blotch mine is created. From January of the subsequent year onwards the larvae are usually fully grown and pupate within their mines, attached to the epidermal layer Phy ilicis puparium.pct. Whereas the mines are mainly on the upper surface of the leaf, the puparia are found on both sides of the leaf. The exact pupation time is variable and depends on the environmental conditions.
HOST PLANT
Ilex aquifolium (European holly).
DISTRIBUTION
Widespread in Europe, introduced into the USA (Oregon, Washington) and Canada.
ECONOMIC IMPORTANCE
Ilex aquifolium is mainly cultivated as ornamental tree. The leaf miner may cause not only some aesthetical damage but can weaken young plants in nurseries. However, the tendency to mass outbreaks is lower than in the related species Phytomyza ilicicola (Eber et al., 2001). Therefore, the economic importance or Ph. ilicis should not be overestimated.