Claire Stephens

ABSTRACT Australia has to date been spared the introduction of highly polyphagous invasive pest agromyzid leafminers; however, their arrival and spread should be considered imminent. To develop a pre-emptive control strategy to deal with exotic leafminer outbreaks the first step is to identify Australian leafmining flies, their plant hosts and their parasitoids to gain an understanding of their population dynamics. Native vegetation may be providing resources for beneficial parasitic wasps plus access to alternative hosts and refuge from disturbance. Here, two Australian endemic saltbushes (Rhagodia candolleana and R. parabolica, Caryophyllales: Chenopodiaceae) have been investigated for their potential to act as reservoirs for endemic agromyzid hosts and their key parasitoids. Mined leaves of the two Rhagodia species were sampled on two commercial horticultural properties in the Virginia horticulture area on the Northern Adelaide Plains between September 2007 and April 2008. Leaf mines on both Rhagodia species were caused by an endemic leafminer species, putatively Phytoliriomyza praecellens Spencer (Diptera: Agromyzidae). Ten species of parasitoids (all Hymenoptera) emerged from R. candolleana mines and seven different species from R. parabolica mines, mainly from the family Eulophidae and with some Pteromalidae and Braconidae. Trigonogastrella Girault sp. (Pteromalidae), Zagrammosoma latilineatum Ubaidillah and Hemiptarsenus varicornis Girault (both Eulophidae) were the most abundant species on R. candolleana, whereas two Opius Wesmael spp. (Braconidae) were the most abundant species on R. parabolica. Findings from this survey suggest an opportunity to plant purpose-designed refuges that could play a role in conservation biological control as part of an Integrated Pest Management strategy developed prior to incursion of pest leafminers such as Liriomyza species.

ABSTRACT The Hymenoptera, insects commonly known as ants, bees, wasps and sawflies, comprise a significant proportion of arthropod diversity in most terrestrial habitats. They are one of the four mega-diverse orders of insects, along with the Coleoptera (beetles), Diptera (flies), and Lepidoptera (moths and butterflies). Over 115,000 species are described worldwide, of which about 11,000 (9.5%) are described from Australia alone. However, the true size of the order might be as much as five times this number. Species of Hymenoptera occur ubiquitously, from forests and woodlands to grasslands and wetlands, freshwater and intertidal zones to urban parks and gardens. Due to the group's diverse biology and ecology no other insect order plays such key roles in the functioning of both natural and agricultural ecosystems. Wasps regulate insect populations though predation and parasitism; bees are among the most important pollinators of flowering plants, and ants dominate many terrestrial landscapes where they are involved in vital ecological processes such as predation, seed dispersal and soil health. The order is normally divided into two suborders: the Symphyta (sawflies) and the Apocrita (comprising all other groups). The Symphyta is largely a northern hemisphere group and is represented in Australasia by only six of 14 families (of which the Siricidae is introduced) and about 180 species, most of which belong to the Pergidae. The Apocrita makes up the vast majority of hymenopteran species, with 61 families occurring in Australasia, four of which are endemic to the region: Austrocynipidae, Austroniidae, Maamingidae and Peradeniidae. The morphology of apocritan wasps differs markedly from that of the Symphyta: Apocrita have a pronounced constriction or waist between the first and second abdominal segments which clearly divides the apparent thorax from the rest of the abdomen. The Australasian Hymenoptera are extremely rich in species, particularly the ants (Formicidae), bees (Apidae), wasps belonging to the families Crabronidae, Mutillidae, Pompilidae, Tiphiidae and Vespidae, and the parasitoid superfamilies Chalcidoidea, Ichneumonoidea and Platygastroidea. The superfamily Cynipoidea is noticeably depauparate in Australasia compared with the northern hemisphere where they are a common group of gall inducers on plants. However, in Australasia this niche appears to be largely taken over by members of the Chalcidoidea. The parasitoid superfamilies are by far the largest in terms of species but overall they are also the poorest studied. They oviposit into or onto the juvenile stages of other insects (as well as other arthropods such as spiders), and the parasitoid larva then feeds on the host to complete its development. This aspect of the biology of parasitic wasps, in conjunction with their often high level of host specificity, has rendered them ideal as biological control agents of a large range of agricultural and horticultural pests.

Can be viewed at: anic.ento.csiro.au/insectfamilies/order_overview.aspx?OrderID=27447&PageID=overview