STUDIES ON THE CEREAL ECOSYSTEM
161
One of the most numerous Carabidae, Risophilw atricapillus, has
been observed by us feeding on apterous aphids.
Although the larger Carabidae were uncommon in the vacuum
samples, pitfall trapping revealed that they were abundant in some
fields. Of these, Nebria brevicollis (F.) was shown by Penny (1966) to
feed on microarthropods, 32% of which were Collembola, 23% Acari
and 38% small nematoceran Diptera; aphids were also eaten. Larvae of
0. frit L. were also taken by N. brevicollis (Jones, 1969). Adult Feronia
melanaria (11.) have been shown to feed on cabbage root fly eggs and
larvae (Wright et al., 1956; Coaker and Williams, 1963).
Although the food of some of the Coccinellidae is poorly known,
other species are well known aphid predators (e.g. D u n , 1949; Banks,
1955). The stomach contents of several P . 14-punctata from the study
area were examined; these consisted of the remains of cereal aphids
and pollen grains. The Coccinellidae were not numerous enough,
however, to have a significant effect on the cereal aphids.
The most important phytophagous Coleoptera belonged to the
Chrysomelidae. Lema melanopa was occasionally common and was
found on wheat, barley and oats. The feeding habits of Qastrophysa
polygoni have already been described (see p. 126). Cassida Jlaveola
was another example of a species which was rare, although its host
plant Stellaria media was abundant in the cereal fields.
Seventeen of the twenty species of Halticini recorded were weed
dwellers. Although three species, Cktocnema hrtensis, Phyllotreta
vittula and Crepidodera ferruginea, fed on cereals the last two species
also fed on other host plants. Of the remaining common species,
Chaetocnema concinna was found on Polygonum spp., Longitarsw
melanocephalus on Plantago spp. and Phyllotreta undulata on Cruciferae.
A number of Meligethes spp. (Nitidulidae) have been recorded,
chiefly from weedy cereal fields. They were commonly found associated
with Sinapis arvensis.
The most common Curculionidae were Apion spp. on clovers and
Ceuthorrhynchw spp. on Sinupis arvensis. I n 1970, 94% of the Curculionidae were seed feeding and 6% leaf eating. In 1971 the figures were
83% and 17% respectively. Leaf eating weevils were mainly Sitona
spp.; Phytonomw was scarce (see p. 113).
3. The relationship between the numbers of macroscopic Collembola and
predatory Coleoptera
We have already seen that the predatory Coleoptera are one of the
most important groups of predators in the cereal ecosystem. Most of
these are more properly members of the soil fauna and are known to
feed on Collembola. The soil Collembola were not counted directly
161
One of the most numerous Carabidae, Risophilw atricapillus, has
been observed by us feeding on apterous aphids.
Although the larger Carabidae were uncommon in the vacuum
samples, pitfall trapping revealed that they were abundant in some
fields. Of these, Nebria brevicollis (F.) was shown by Penny (1966) to
feed on microarthropods, 32% of which were Collembola, 23% Acari
and 38% small nematoceran Diptera; aphids were also eaten. Larvae of
0. frit L. were also taken by N. brevicollis (Jones, 1969). Adult Feronia
melanaria (11.) have been shown to feed on cabbage root fly eggs and
larvae (Wright et al., 1956; Coaker and Williams, 1963).
Although the food of some of the Coccinellidae is poorly known,
other species are well known aphid predators (e.g. D u n , 1949; Banks,
1955). The stomach contents of several P . 14-punctata from the study
area were examined; these consisted of the remains of cereal aphids
and pollen grains. The Coccinellidae were not numerous enough,
however, to have a significant effect on the cereal aphids.
The most important phytophagous Coleoptera belonged to the
Chrysomelidae. Lema melanopa was occasionally common and was
found on wheat, barley and oats. The feeding habits of Qastrophysa
polygoni have already been described (see p. 126). Cassida Jlaveola
was another example of a species which was rare, although its host
plant Stellaria media was abundant in the cereal fields.
Seventeen of the twenty species of Halticini recorded were weed
dwellers. Although three species, Cktocnema hrtensis, Phyllotreta
vittula and Crepidodera ferruginea, fed on cereals the last two species
also fed on other host plants. Of the remaining common species,
Chaetocnema concinna was found on Polygonum spp., Longitarsw
melanocephalus on Plantago spp. and Phyllotreta undulata on Cruciferae.
A number of Meligethes spp. (Nitidulidae) have been recorded,
chiefly from weedy cereal fields. They were commonly found associated
with Sinapis arvensis.
The most common Curculionidae were Apion spp. on clovers and
Ceuthorrhynchw spp. on Sinupis arvensis. I n 1970, 94% of the Curculionidae were seed feeding and 6% leaf eating. In 1971 the figures were
83% and 17% respectively. Leaf eating weevils were mainly Sitona
spp.; Phytonomw was scarce (see p. 113).
3. The relationship between the numbers of macroscopic Collembola and
predatory Coleoptera
We have already seen that the predatory Coleoptera are one of the
most important groups of predators in the cereal ecosystem. Most of
these are more properly members of the soil fauna and are known to
feed on Collembola. The soil Collembola were not counted directly