STUDIES ON THE CEREAL ECOSYSTEM
145
I n 1970 approximately 65% of the Diptera were classified as phytophagous, mainly due to the large numbers of wheat blossom midges
present in the crops in that year, whilst 25% belonged to category (2).
The most important of these were the mycetophagous and saprophagous
forms. In 1971 the relatively high number of Drosophilidae and
Lonchopteridae resulted in a large proportion (56%) of the fauna
being classified as mainly saprophagous and mycetophagous. The
proportion (26%) of phytophagous Diptera was lower than in 1971.
I n both I970 and 1971 haematophagous and parasitic Diptera constituted less than 1 % of the dipterous fauna. Predators were relatively
scarce in both years, particularly in 1970.
If we consider even the most important members of the dipterous
fauna it is surprising how little is known of their biology. According to
Smith (1969), adult Lonchoptera occur in humid places, often near
water or in shady woods. Very little is known about the habits of the
immature stages, but they appear to live among dead leaves and decaying vegetable matter (Smith, loc. cit.). The Drosophilidae were
represented by two Drosophila species and also by Parascaptomyza
pallida Zett. According to Collin (1953), the larvae of P. pallida live in
decaying vegetable matter.
There is probably more information on the feeding habits of predatory Diptera. Although some predators may be limited to feeding
on one or a few species of prey, many take a wide range of food. For
example, the one asilid species so far recorded, Dioctria rujipes Deg.,
is known to feed on Hymenoptera, especially Ichneumonidae (Colyer
and Hammond, 1968), as well as other Diptera. The commonest
Empididae present in the cereal fields were Platypalpus spp., Tachydromia spp., Empis livida L. and more rarely E. tessellata F. The prey
of the latter species has been recorded by Hobby and Smith (1961), and
although small Diptera are usually taken, larger items such as Tachinidae and Scatophagidae are frequently included. Species of Platypalpus
and Tuchydromia were observed by us feeding on many small Diptera in
the field, including Oscinella frit and Chlorops sp. In addition Tachydromia species were seen to take apterous aphids.
The other important dipterous predators consisted chiefly of
Dolichpus sp. and Medeterus sp. (Dolichopodidae) and Scatophaga
stercorarium (L.) (Scatophagidae). At least in some circumstances
Dolichopodidae, for example the Australian Chrysosoma micans, will
eat aphids (Hughes, 1972). The prey of the dung fly S. stercorarium has
been documented by Hobby (1933). This species appeared to be quite
an important predator in certain parts of the study area, especially in
1972.
The Syrphidae were scarce in 1970 and 1971. The most numerous
145
I n 1970 approximately 65% of the Diptera were classified as phytophagous, mainly due to the large numbers of wheat blossom midges
present in the crops in that year, whilst 25% belonged to category (2).
The most important of these were the mycetophagous and saprophagous
forms. In 1971 the relatively high number of Drosophilidae and
Lonchopteridae resulted in a large proportion (56%) of the fauna
being classified as mainly saprophagous and mycetophagous. The
proportion (26%) of phytophagous Diptera was lower than in 1971.
I n both I970 and 1971 haematophagous and parasitic Diptera constituted less than 1 % of the dipterous fauna. Predators were relatively
scarce in both years, particularly in 1970.
If we consider even the most important members of the dipterous
fauna it is surprising how little is known of their biology. According to
Smith (1969), adult Lonchoptera occur in humid places, often near
water or in shady woods. Very little is known about the habits of the
immature stages, but they appear to live among dead leaves and decaying vegetable matter (Smith, loc. cit.). The Drosophilidae were
represented by two Drosophila species and also by Parascaptomyza
pallida Zett. According to Collin (1953), the larvae of P. pallida live in
decaying vegetable matter.
There is probably more information on the feeding habits of predatory Diptera. Although some predators may be limited to feeding
on one or a few species of prey, many take a wide range of food. For
example, the one asilid species so far recorded, Dioctria rujipes Deg.,
is known to feed on Hymenoptera, especially Ichneumonidae (Colyer
and Hammond, 1968), as well as other Diptera. The commonest
Empididae present in the cereal fields were Platypalpus spp., Tachydromia spp., Empis livida L. and more rarely E. tessellata F. The prey
of the latter species has been recorded by Hobby and Smith (1961), and
although small Diptera are usually taken, larger items such as Tachinidae and Scatophagidae are frequently included. Species of Platypalpus
and Tuchydromia were observed by us feeding on many small Diptera in
the field, including Oscinella frit and Chlorops sp. In addition Tachydromia species were seen to take apterous aphids.
The other important dipterous predators consisted chiefly of
Dolichpus sp. and Medeterus sp. (Dolichopodidae) and Scatophaga
stercorarium (L.) (Scatophagidae). At least in some circumstances
Dolichopodidae, for example the Australian Chrysosoma micans, will
eat aphids (Hughes, 1972). The prey of the dung fly S. stercorarium has
been documented by Hobby (1933). This species appeared to be quite
an important predator in certain parts of the study area, especially in
1972.
The Syrphidae were scarce in 1970 and 1971. The most numerous