The Wharton Lab

Opius oophilus Fullaway is a junior synonym (Wharton and Gilstrap 1983), and all of the biological control literature prior to about 1985 used the name oophilus.
Prior to the description of Fopius, the species now placed in this genus were most frequently included either in Opius or Biosteres. This particular species has also been placed, occasionally, in Diachasma. Thus, the names Opius oophilus, Biosteres oophilus, and Diachasma oophilus all refer to Fopius arisanus.

Members of the persulcatus species group (to which Fopius arisanus belongs) are characterized by the presence of striate sculpture on the second metasomal tergum (as in Fig. 8) and a frons that is densely covered with large punctures, giving the frons a somewhat rugose appearance (Figs. 3 and 4). This species is further characterized by generally dark abdomen and thoracic pleura and the absence of a ridge apically on the dorsal valve of the ovipositor.

Relationships among members of the genus Fopius have been briefly discussed by Wharton (1999).

This species oviposits in the egg of the host. It is an egg-prepupal parasitoid, eventually emerging from the host puparium shortly after the latter is formed (killing the host before pupation takes place). Initial work on the biology of this species was published by van den Bosch et al. (1951), van den Bosch and Haramoto (1951), van den Bosch and Haramoto (1953), Hagen (1953), and Haramoto (1957). More recent studies include those of Snowball et al. (1962), Kaya and Nishida (1968), Wong et al. (1984), Williams et al. (1988), Ibrahim et al. (1992), Ramadan et al. (1992), Bautista and Harris (1996), Bautista et al. (1999) (mass rearing), Quimio and Walter (2000), Quimio and Walter (2001), Harris and Bautista (2001), Bautista et al. (2001), Vargas et al. (2002), Baeza-Larios et al. (2002), Falco et al. (2003), Wang and Messing (2003), and Altuzar et al. (2004). Wang and Messing (2003) explored the effects of several factors (indirect host stimuli, food supply, and mating status) on egg maturation in female F. arisanus, and found that only oviposition experience was directly associated with an increase in egg maturation. The authors suggest that providing laboratory-reared F. arisanus females with a constant supply of host eggs may increase parasitoid offspring in mass rearing, and maximize field parasitism of hosts after release. Additional experiments indicated that intraspecific competition occurs in superparasitized medfly eggs, resulting in high mortality of supernumerary F. arisanus eggs and first instar larvae by physiological suppression (Wang and Messing 2003).

Fopius arisanus has achieved a competitive advantage over other introduced parasitoid species in Hawaii. Wang and Messing (2003) have shown several mechanisms by which F. arisanus optimizes its parasitization capabilities including adjusting foraging time according to patch quality cues (presence of plant injury odors, kariomones, and previous experience in patch), utilizing a fixed set of host location behaviors (antennating, probing, detecting, and ovipositing), and discriminating nonparasitized from parasitized hosts for oviposition.

Similar to results from previous experiments with Diachasmimorpha tryoni (Wang and Messing 2003), Diachasmimorpha krausii, and Psyttalia concolor (Wang and Messing 2002), Wang et al. (2003) found that F. arisanus was the superior competitor when matched with Diachasmimorpha longicaudata. As an egg parasite, F. arisanus arrives on the host (Ceratitis capitata and Bactrocera dorsalis in these experiments) prior to D. longicaudata, a larval parasite, and suppresses development of D. longicaudata, primarily at the egg stage. The authors also report that in experiments with the 4 larval parasitoids none were able to directly destroy F. arisanus larvae during parasitism. Although a superior competitor among many fruit fly parasitoids, F. arisanus does not flourish in all environments including higher elevations and lower temperatures, and is not adapted to certain tephritid hosts including Bactrocera cucurbitae. These recent studies verify and expand on the earlier studies of interspecific competition by van den Bosch and Haramoto (1951), van den Bosch and Haramoto (1953) and Bess et al. (1961). For a detailed review of the biology of this species, see Rousse et al. (2005).

Native to the Indo-Pacific Region, from at least India to Taiwan. This species was originally described from Taiwan.

Fullaway described Opius oophilus on the basis of specimens collected in Hawaii following the introduction of this species against Oriental fruit fly in the late 1940s, but oophilus was later recognized as a synonym of arisanus, originally described from Taiwan. The actual country of origin for the material introduced to Hawaii is uncertain (though believed to be Malaysia). Fopius arisanus has subsequently become established in several other countries, including Australia, Costa Rica, Fiji, and Mauritius (Wharton et al. 1981, Wharton and Gilstrap 1983) as a result of purposeful redistribution from Hawaii targeting a variety of pest tephritids (Wharton 1989). For a more recent summary, see Rousse et al. (2005).

See additional comments under the Fopius persulcatus species group on the Fopius page. An overview of the biology of this species has been published by Rousse et al. (2005)