Biological Control of Insect Pests: Southeast Asian Prospects - EcoPort

Biology of main natural enemies
4.5 Cosmopolites sordidus 103
Dactylosternum abdominale Col.: Hydrophilidae
This is the most effective predator in Kenya. Its larvae are polyphagous
predators and consume the contents of C. sordidus larvae and at high
predator density may become cannibalistic. They also feed on the microfauna
and micro-flora of decomposing plant tissues. On the other hand, the
adults cause significant mortality of C. sordidus eggs; although many are
laid in inaccessible positions inside the pseudostem and the polyphagous
adults do not specifically search for eggs. Adults cannot penetrate the
narrow tunnels of young larvae, so can only capture newly hatched larvae:
later instar larvae are not attacked (Koppenhšfer and Schmutterer 1993;
Koppenhšfer et al. 1992, 1995). Development from egg to adult takes 17 to
33 days, life span is 95 days and females lay an average of 1.7 egg cases per
week, each case containing 4 eggs. The preoviposition period is 16.6 days
(Koppenhšfer et al. 1995).
Geotomus pygmaeus Hem.: Cydnidae
This predator is recorded from India, Ceylon, Myanmar, Indonesia,
Vietnam, China, Japan, New Caledonia, Fiji, Samoa, French Polynesia and
Hawaii. Its extensive distribution is probably due to its ready transportation
in the soil attached to the roots of cultivated plants. Although reported to
attack C. sordidus eggs in Malaysia, China (1935) suggests that this species
normally is unlikely to be a predator.
Plaesius javanus Col.: Histeridae
The predatory larvae and adults of this Indonesian beetle attack larvae and
pupae of Cosmopolites sordidus and many other soil and litter-inhabiting
insects. Eggs are laid singly in old banana stumps, at the base of the stem and
on the rhizome below the soil surface. The eggs hatch in 8 to 9 days,
producing active, voracious larvae which feed for 5 to 6 months, older larvae
being capable of consuming up to 30 or more C. sordidus larvae per day. A
prepupal period of 10 to 15 days is passed in a pupation cell constructed in
the soil, followed by a pupal stage of about 14 days. The adult remains in the
cell for 7 to 10 days before emerging and is then capable of consuming 7 or 8
weevil larvae per day (Clausen 1978; Jepson 1914; Weddell 1932).
Thyreocephalus interocularis Col.: Staphylinidae
This is the second most effective predator on C. sordidus larvae in Kenya.
Both adults and larvae are polyphagous. In the absence of other hosts adults
may prey on their own larvae and larvae are also occasionally cannibalistic
(Koppenhšfer and Schmutterer 1993). After a pre-oviposition period of 32
days, females lay an average of 31 eggs in decomposing banana