BTUDIEB ON THE INSECT FAUNA ON SCOTCH BROOM
141
were parmitised by the four scelionids. A t Silwood, 206 eggs of Pierodomu, were left exposed on broom in Area 1 and 120 were parasitid
by fhbx.9 spp. The biology of these minute wasps is of considerable
interest and mme of the related epecies of genus Aedcue are economically important, as they are used in the biological control of the Sunn
Pest, Euygmter integricep.
VI. PHYTOPHAGOUS INSECTS; STEM MINERS
The biology of four species of broom stem miners and of their parasites has been studied in varying degrees of detail. The larvae of two
of the species of the curculionid beetle, Apion immune, Kirby and of
the minute moth, Leucqtera 8partifolie&z Hiibner form mines in
young green twigs. The other two species studied were the scolytid
beetles, Phloeophthurw rhododactylzre (Marsh.) and Hdystinw ob8curms
(Marsh.) the larval and adult stages of which live in galleries in woody
stems. Phloeqphthurw attacks dying and recently dead wood and
although it is known to attack gorse, i t has never been found on this
shrub L*t Silwood. Unlike Phloeophtiumcs, Halydinwr never attacked
dead wood but usually formed galleries in very old bushes, nearly
alwayg only on the main stem.
Leucoptera aprtifoliellu is one of the most abundant insect species on
broom, locally its numbers being only second to those of payllids and
aphids. It is this species that is being experimentally used to check the
spread of broom in California, where the shrub has become a weed of
range and forest lands (Holloway, 1964a; Frick, 1964).
A. THE BIOLOGY OF &on immune KIRBY (Williams, 1966)
1. The life cycle
The biology of several Apion species and amongst them of A. immune
was studied by Williams (1966) from 1963 to 1966. Apion immune is a
polyvolthe epeoies without a diapause in any stage of its life cycle. It
is difficult to say how many annual generations it hm, a~ they overlap
and all the stages occur simultaneously throughout the year. Food for
adults and larvae in the form of green twigs is available at all s e w n s
and the alimentary canals of adults collected in winter contained freshly
eaten broom. Moat A. immune occurred on young buehee, or on bushes
with green succulent shoote of the current year’s growth. They were
rarely collected on old, dying or on dead bushes.
Dissections and examination of the reproductive organs indicated
that old females which had ovipositgd throughout the summer died off
by late summer, leaving behind a new generation of dulte that overwinter. Young females begin to mature in November and to lay eggs
141
were parmitised by the four scelionids. A t Silwood, 206 eggs of Pierodomu, were left exposed on broom in Area 1 and 120 were parasitid
by fhbx.9 spp. The biology of these minute wasps is of considerable
interest and mme of the related epecies of genus Aedcue are economically important, as they are used in the biological control of the Sunn
Pest, Euygmter integricep.
VI. PHYTOPHAGOUS INSECTS; STEM MINERS
The biology of four species of broom stem miners and of their parasites has been studied in varying degrees of detail. The larvae of two
of the species of the curculionid beetle, Apion immune, Kirby and of
the minute moth, Leucqtera 8partifolie&z Hiibner form mines in
young green twigs. The other two species studied were the scolytid
beetles, Phloeophthurw rhododactylzre (Marsh.) and Hdystinw ob8curms
(Marsh.) the larval and adult stages of which live in galleries in woody
stems. Phloeqphthurw attacks dying and recently dead wood and
although it is known to attack gorse, i t has never been found on this
shrub L*t Silwood. Unlike Phloeophtiumcs, Halydinwr never attacked
dead wood but usually formed galleries in very old bushes, nearly
alwayg only on the main stem.
Leucoptera aprtifoliellu is one of the most abundant insect species on
broom, locally its numbers being only second to those of payllids and
aphids. It is this species that is being experimentally used to check the
spread of broom in California, where the shrub has become a weed of
range and forest lands (Holloway, 1964a; Frick, 1964).
A. THE BIOLOGY OF &on immune KIRBY (Williams, 1966)
1. The life cycle
The biology of several Apion species and amongst them of A. immune
was studied by Williams (1966) from 1963 to 1966. Apion immune is a
polyvolthe epeoies without a diapause in any stage of its life cycle. It
is difficult to say how many annual generations it hm, a~ they overlap
and all the stages occur simultaneously throughout the year. Food for
adults and larvae in the form of green twigs is available at all s e w n s
and the alimentary canals of adults collected in winter contained freshly
eaten broom. Moat A. immune occurred on young buehee, or on bushes
with green succulent shoote of the current year’s growth. They were
rarely collected on old, dying or on dead bushes.
Dissections and examination of the reproductive organs indicated
that old females which had ovipositgd throughout the summer died off
by late summer, leaving behind a new generation of dulte that overwinter. Young females begin to mature in November and to lay eggs