ABSTRACT
The completion of a data matrix (White and Hancock 1997) of coded descriptions of IndoAustralasian Dacini* provided an ideal opportunity to analyze character distributions and correlations. The purpose of this chapter is to discuss characters used for classification and identification of dacine fruit flies from the perspective of their behavior. In addition, a preliminary reanalysis of the classification is carried out and a number of previously undocumented observations of potential interest to the study of dacine behavior are reported. The small genera
Ichneumonopsis
** (one species) and
Monacrostichus
(two species) are not considered in detail here (see Drew and Hancock 1994b and Chapter 19), leaving only
Bactrocera
and
Dacus
with 447 and 57 species, respectively. White and Hancock (1997) covered all described and valid species of Dacini from the Oriental, Australasian, and Oceanic Regions, plus some species from the Afrotropical Region (all Mascarene species and African pest species), making a total of 507 species. A further 7
Bactrocera
and 161
Dacus
spp. are known from the Afrotropical Region but were not included by White and Hancock
(1997) and another 17 Asian
Dacus
spp. were recently described by Drew et al. (1998), bringing the totals to 454
Bactrocera
spp. and 235
Dacus
spp. They are therefore omitted from the analyses given here, although their inclusion would not be expected to alter the conclusions greatly since species of most subgenera of
Dacus
are included. Many of the characters for which we have some understanding of function have been used in
the construction of the subgeneric classification. The subgeneric distribution of these characters is therefore presented here as a basis for discussion (Table 20.1). The classification used by White and Hancock (1997) derives from Drew’s (1989) monograph on the Australasian-Oceanic fauna, but with a few minor modifications to allow for inclusion of the Oriental fauna and newly discovered information (see Figure 20.6). Drew (1989) placed most Indo-Australasian species that had previously been classified as
Dacus
into the genus
Bactrocera
(a name formerly used for a subgenus, known as
Strumeta
in the older literature). This was based on the fact that most species with fused terga (those still called
Dacus
) were Afrotropical and mostly associated with just two plant families, Asclepiadaceae and Cucurbitaceae. The Indo-Australasian group formerly known as the genus
Callantra
have the same pattern of host association and fused terga, so they were placed as a subgenus of
Dacus
. The species with nonfused terga, that is, the genus
Bactrocera
, were subdivided into four groups of subgenera according to the length of the posterior lobe of the male lateral surstylus and the presence or absence of a notch in the hind margin of male sternite 5. Most species (all except eight), belong to two of those groups; the
Zeugodacus
group of subgenera are predominantly associated with Cucurbitaceae; the
Bactrocera
group of subgenera rarely attack cucurbits and include some species which attack a very wide range of plant families, for example, the Oriental fruit fly,
B. dorsalis
(Hendel). One of the most outstanding features of the biology of the Dacinae (at least the Dacini and
Ceratitidini) is that the males of many species are attracted to so-called male lures, that is, chemicals that are not pheromones but are nonetheless very potent male attractants of value for control through male suppression, for population monitoring and taxonomic survey. The chemicals that attract Dacini are known as methyl eugenol, cue-lure, and vert-lure, although the latter is only known to attract one species (see White and Elson-Harris 1994 for details of all major lures). Species in the
Bactrocera
group of subgenera respond to either methyl eugenol or cue-lure and in some cases lure response is the only tenable diagnostic feature for the identification of males. Conversely, in the
Zeugodacus
group and the genus
Dacus
, methyl eugenol response is rare. The pecten (row of long setae placed transversely, close to side of hind margin of tergite 3), plus a suite of correlated morphological features, appear to be involved in pheromone dispersal and it has been shown that male lures augment the effects of pheromones. Many of the same suite of characters are involved in sound production and the taxonomic distribution of these characters is discussed with respect to that behavior later in this chapter.
