Insects - Pests of Ornamental Trees, Shrubs and Flowers - page 203

Hepialus humuli (Linnaeus) ( 474-476 )
Ghost swift moth
A widely distributed and generally common species,
infesting a similar range of hosts to the previous species
but usually more damaging to grassland, pastures and
lawns. The larvae (up to 50 mm long) are whitish,
robust and relatively opaque, with a reddish-brown head
and prothoracic plate, and prominent, dark brown
pinacula (cf. Hepialus lupulinus ). When young, they
feed on plant rootlets but older individuals attack the
larger roots and also bite into stolons and the lowermost
parts of stems. In common with the previous species,
individuals construct silk-lined feeding tunnels in the
soil, retreating into them or curling up if disturbed. The
larvae consume large amounts of food but growth is
slow, the period of development usually extending over
two, and occasionally three, years. Damage to plants is
particularly severe in the second summer of larval
growth, individuals then pupating in the following April
or May. Adults occur mainly in June and July, and are
active at dusk. The females are relatively large
(50-70 mm wingspan), with yellowish-ochreous,
orange-marked fore wings; males are much smaller
(46-50 mm wingspan), with silvery-white wings.

Each female lays up to 300 eggs which she broadcasts
at random whilst in flight. Larvae feed in the soil on the
roots of grasses and many other plants. If disturbed, the
larvae retreat rapidly backwards down narrow, feeding
burrows, but they are readily unearthed during soil
cultivation. Larval development continues throughout
the winter. Larvae usually pupate in the following April,
each in a loosely woven silken tunnel formed among the
root system of the host. Adults emerge about six weeks
later, and often appear in distinct flushes after rainfall.

DAMAGE
Larvae bite off the roots and tunnel into bulbs, corms,
rhizomes and tubers of hosts with fleshy underground
root systems. This retards growth and often causes
plants to wilt; badly damaged plants may be killed. If
unchecked, infestations on perennial hosts may persist
and increase in importance from year to year. Most
serious damage is caused in autumn, winter and early
spring, and is often experienced when plants are grown
in recently ploughed pasture or grassland.

473 474

473 Larva of garden swift moth ( Hepialus lupulinus ). 474 Female ghost swift moth ( Hepialus humuli ).

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475 Male ghost swift moth ( Hepialus humuli ). 476 Larva of ghost swift moth ( Hepialus humuli ).