BTUDIES ON THB INSEOT FAUNA ON BcoToH B&OOM
179
and are the prey of predacious arthropods, particularly of spiders. The
other oommon prey include the coIeopteran and lepidopteran eggs and
larvae, mitm, Collemhola, Thysanoptora, P m p t e r a and in some years
cocoid nymphs. It is of incidental interest that in less than a hectare of
broom (Area 1 ) we collected over a quarter of all the British species of
Psocoptera (Richards and Waloff, 1958). But the populations of psocids
are relatively small and the psyllids and aphids greatly outnumber any
other poaaible prey.
Before the precipitin test was extensively used on the arthropod predators, their importance had already been streased in earlier work of
Collyer (1953a, b) and of Mace (1965). B. I). Smith (1966a), whom work
on broom aphids extended between 195&58 was able to demonstrate
their relative ineffectiveness when aphids were abundant and their
importance when the populations of dcyrthosiph were low.
B. BIONOYICS OR' SOME PBEDAUIOUS ABTHBOPODS
ON BBOOY
1. Angstia baccalum (L.)
This red mite, which is abundant on broom bushes and in broom
litter was studied by Baker (1962), who concluded that A. bacmrurn (L.)
and A. agilis Banks are probably the same species.
A. baccarum ia by no means restricted to broom. It is probably univoltine in Britain and oviposita in the top 15 cm of broom litter and soil
in July. The nymphs and adults on broom are highly predacious and
will attack any small prey. However, the mite is unable to pierce the
waxy layer of PeyUa eggs embedded in b m m atems.
The only predators of Anystis that were identified in the field were
the immature stages of spiders.
2. Aphkbphuqm Syrphidae on broom
Dixon (1959) investigated the relationship between the number of
aphids and aphidophagous Syrphidae on broom. The most common
species of Syrphids were Plutycheirus scutatus (Meigen), Syrphus luniger
Meigen, S . nitidicollia Meigen and S . vitripennis Meigen. Adult syrphids
feed on pollen and each year the greatest number were trapped at the
time when broom was in flower. With the exception of S. nitidimtZ+ all
the recorded species were polyvoltine, but on broom they lay eggs in
spring and rarely after. This implies that the succeeding generations
develop on other species of aphid-infested plants.
The peak of abundance of syrphid eggs preceded that of Acydhosiphon spartii, although oviposition took plaw preferentially on the
most debely infested bushes, an example of this is given in Table LIII.
179
and are the prey of predacious arthropods, particularly of spiders. The
other oommon prey include the coIeopteran and lepidopteran eggs and
larvae, mitm, Collemhola, Thysanoptora, P m p t e r a and in some years
cocoid nymphs. It is of incidental interest that in less than a hectare of
broom (Area 1 ) we collected over a quarter of all the British species of
Psocoptera (Richards and Waloff, 1958). But the populations of psocids
are relatively small and the psyllids and aphids greatly outnumber any
other poaaible prey.
Before the precipitin test was extensively used on the arthropod predators, their importance had already been streased in earlier work of
Collyer (1953a, b) and of Mace (1965). B. I). Smith (1966a), whom work
on broom aphids extended between 195&58 was able to demonstrate
their relative ineffectiveness when aphids were abundant and their
importance when the populations of dcyrthosiph were low.
B. BIONOYICS OR' SOME PBEDAUIOUS ABTHBOPODS
ON BBOOY
1. Angstia baccalum (L.)
This red mite, which is abundant on broom bushes and in broom
litter was studied by Baker (1962), who concluded that A. bacmrurn (L.)
and A. agilis Banks are probably the same species.
A. baccarum ia by no means restricted to broom. It is probably univoltine in Britain and oviposita in the top 15 cm of broom litter and soil
in July. The nymphs and adults on broom are highly predacious and
will attack any small prey. However, the mite is unable to pierce the
waxy layer of PeyUa eggs embedded in b m m atems.
The only predators of Anystis that were identified in the field were
the immature stages of spiders.
2. Aphkbphuqm Syrphidae on broom
Dixon (1959) investigated the relationship between the number of
aphids and aphidophagous Syrphidae on broom. The most common
species of Syrphids were Plutycheirus scutatus (Meigen), Syrphus luniger
Meigen, S . nitidicollia Meigen and S . vitripennis Meigen. Adult syrphids
feed on pollen and each year the greatest number were trapped at the
time when broom was in flower. With the exception of S. nitidimtZ+ all
the recorded species were polyvoltine, but on broom they lay eggs in
spring and rarely after. This implies that the succeeding generations
develop on other species of aphid-infested plants.
The peak of abundance of syrphid eggs preceded that of Acydhosiphon spartii, although oviposition took plaw preferentially on the
most debely infested bushes, an example of this is given in Table LIII.