Predators

birds

Obviously large larvae, like those of mining sawflies, must be an attractive prey for insectivorous birds. This was testified by Heterarthrus nemoratus; this species was around 1920 inadvertently introduced from Europe into the United States, and built up immense populations in a relatively short time. Around 50% of the larvae were eaten then by birds (Brower, 1934a).

Especially tits are well known predators of miners (Ellis, 2000a; Hespenheide, 1991a; Owen, 1975a). A mine that has been handled by a bird has a characteristic V-shaped opening.

Tischeria ekebladella bird predation

Tischeria ekebladella op eik

Especially in suburban situations bird predation on Phytomyza ilicis can be conspicuous. The birds are able to locate the puparia with impressive precision: a second stab is never necessary. I more natural settings however bird predation seems to have a negligible effect on the population (Gripenberg & Roslin, 2008a).

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Phytomyza ilicis on Holly

lacewings

Lacewing larvae have long and thin, hollow, mandibles which are used to stab and suck out aphids, insect eggs and the like. Here a miner has been stabbed through the wall of its mine. The shrivelled remains of the victim are vaguely visible.

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Tischeria ekebladella on Oak

ichneumon flies

It is known that ichneumon flies not only attack their prey by laying an egg on them, with the well-known results. From time to time an ichneumon fly also attacks an insect with its mandibles, biting and squeezing it, and drinking the juices that are extruded; this behaviour is known as adult feeding. It has been observed that also mining larvae have been attacked in this way, through the wall of their mine.

spiders

Also some ambulatory spiders have been seen to attack leaf miners. Apparently they are able to register the presence of the miner by its movements. Sometimes they drag the larva out of the mine, at other occasions the prey is consumed through the wall of the mine (Amalin ao, 2001a).

earwigs and ants

Predatory insects, in particular earwigs and ants, attack leaf mines as well. Hering (1967a) found indications of heavy mortality by ants in Dalmatia; Koricheva, Lappalainen & Haukioja (1995a) found in Scandinavia many signs of ant predation on Eriocrania mines. The main indications for this type of mortality is a mine that has been torn open, from which the larva or pupa is missing.

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Phyllonorycter coryli on Hazel

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Fenusa pumila on Birch

earthworms

Earthworms pull rotting leaves into their burrows, and devour them. For those miners that hibernate within their mines being pulled underground poses a severe threat. Laing ao (1986a) found that in years with a could spring, when Phyllonorycter blancardella emerges only late from its pupa, a considerable proportion of the pupae perishes below ground.

grazers and mowers

Overgaard Nielsen discovered that indiscriminate feeding by the very numerous caterpillars of the small winter moth forms an important mortality for Orchestes fagi. This of course is but a natural form of the destruction caused by mowing. Everyone interested in mines or galls knows that a roadside, once is has been mowed, is uninteresting for the rest of the summer.

references

Amalin, Reiskind, Pena & McSorley (2001a), Brower (1934a), Ellis (2000a), Gripenberg & Roslin (2008a), Hering (1957a), Hespenheide (1991a), Koricheva, Lappalainen & Haukioja (1995a), Laing, Heraty & Corrigan (1986a), Overgaard Nielsen (1968a), Owen (1975a).

16.x.2009

mod 2.viii.2017