THE AUSTRALIAN NATIONAL UNIVERSITY _________________________________________________________________________________ Research School of Biology Division of Evolution, Ecology & Genetics CANBERRA ACT 0200 AUSTRALIA TELEPHONE: +61 26 125 2873 FACSIMILE: +61 26 125 5573 EMAIL: [email protected] 7 February 2014 To whom it concerns, Dr Gabor Neumann has asked me to provide documentation on the identity of dead, preserved lac insects (order Hemiptera, superfamily Coccoidea, family Kerriidae; formerly Tachardiidae) that were sent to me for taxonomic identification. All specimens from Australia (Christmas Island) and Malaysia (Klang in Selangor and Sarawak in Borneo) have morphology consistent with that of Tachardina aurantiaca (Cockerell), which is a common species in Southeast Asia. This species was named and described in 1903 from specimens collected on citrus in Java, Indonesia. Subsequent publications record this species from Australia (Christmas Island), Malaysia, the Maldives, Singapore and Thailand. All other species of the genus Tachardina occur in Africa and thus it is relatively easy to distinguish T. aurantiaca from other lac insects present in Southeast Asia. The only published taxonomic descriptions and illustrations of T. aurantiaca that are useful for morphological identification are by Chamberlin (1923) and Lit (2002). The latter is an unpublished chapter in a PhD thesis of one of my former students. I identified the adult female specimens from Christmas Island and Malaysia by examination of the insect cuticle (“skin”) under a compound microscope. This required the body contents of the specimens to be cleared (removed) by soaking for 24 hours in 10% potassium hydroxide, and then the cleaned cuticles were stained and dehydrated before being mounted in a resin on a microscope slide. The features useful for identification can only be seen under high magnification on the compound microscope. Tachardina aurantiaca is distinguished from other lac insects by a combination of morphological features, including the four-sectored anal ring, the presence of two secondary depressions on the brachial plate and the shape and composition of the marginal duct clusters. There had been no recent collection and study of T. aurantiaca until the work of Dr Neumann and his colleagues and associates. Regards, Dr P.J. Gullan Emeritus Professor Literature cited Chamberlin, J.C. (1923) A systematic monograph of the Tachardiinae or lac insects (Coccidae). Bulletin of Entomological Research 14: 147–212. Lit, I.L., Jr (2002) Morphology, Systematics and Phylogeny of the Lac Insects (Kerriidae, Coccoidea, Hemiptera). Doctor of Philosophy thesis, University of the Philippines Los Baños, Philippines. 286 pp. RESEARCH AND DEVELOPMENT OF BIOLOGICAL CONTROL FOR SCALE INSECTS: INDIRECT CONTROL OF THE YELLOW CRAZY ANT ON CHRISTMAS ISLAND, 2009‐2013 Peter T. Green, Dennis J. O’Dowd, Gabor Neumann, and Sarah Wittman Department of Botany, La Trobe University, Bundoora, Vic 3086 Final Report to the Director of National Parks 3 July 2013 1 Executive Summary Research Project 1. YCA dependence on honeydew Project 1a. Honeydew use by YCA. Successful biological control of the yellow lac scale Tachardina aurantiaca could remove a large fraction (an average of 70% to an average of 87%, depending on assumptions) of honeydew available to the yellow crazy ant. However, there is considerable site‐to‐ site variation in the likely contribution of T. aurantiaca to the total honeydew economy, and it is not certain that targeting this species alone would provide adequate indirect control for the YCA in all supercolonies. The most prudent course of action is to target the entire assemblage of honeydew‐ producing scale insects through the introduction of a biological control agent for T. aurantiaca, complemented by the use parasitoids already present on Christmas Island to target the coccoid soft scales. Project 1b. Stable Isotope Analysis. Stable isotope analyses of YCA workers, plants, herbivores and predators collected from four declining supercolonies in 2010‐2011 indicate that at supercolony densities, a substantial fraction of YCA dietary intake is plant‐derived. This is consistent with the idea that YCA supercolonies depend heavily on honeydew derived from scale insects for a large fraction of colony food and energy requirements, and provides support for the idea that indirect control over YCA supercolonies could be achieved by targeting honeydew‐producing scale insects for biological control. Project 1c. Scale Insect Removal Experiment. The exclusion of YCA from access to scale insects at a large experimental field site caused YCA activity on the ground to decline 5‐fold within 4 weeks, compared to pre‐treatment levels. This large field experiment validates the key concept of indirect biological control for YCA on Christmas Island; exclusion of honeydew‐producing scale insects from YCA caused a significant and substantial reduction in YCA abundance on the ground. Project 1d. Carbohydrate supply and YCA growth and behaviour. Dynamics and behaviour of YCA in laboratory colonies depended on carbohydrate supply. When sugar supply was elevated, reproductive output by queens increased, death rates of workers decreased, foraging tempo quickened, and interspecific aggression intensified. These results suggest that sugar supply, through honeydew supplied from scale insects, plays an important role in YCA supercolony dynamics, foraging efficiency, and interspecific aggression. Research Project 2. Scale insects and natural enemies Projects 2a and 2c. Natural enemies survey, parasitization rates of lac scale insects (Tachardina aurantiaca and Paratachardina pseudolobata) and parasitoid behaviour in area of origin (Southeast Asia) and on Christmas Island. Few natural enemies of the key honeydew‐producing scale insect Tachardina aurantiaca occur on Christmas Island, and they do not regulate its population size. No parasitoids of female T. aurantiaca were found. Conversely, within its native range in Malaysia, T. aurantiaca is rare and patchily distributed, associated with diverse natural enemies, including at least five species of primary parasitoids, and it suffers high parasitization rates – all attributes consistent with population regulation by natural enemies. Importantly, high parasitism rates in Malaysia occurred in the presence of honeydew‐collecting ants, including the yellow crazy ant. Of the primary parasitoids known to attack yellow lac scale from our studies in Malaysia, 2 Tachardiaephagus somervillei (Encyrtidae) is the most promising agent for introduction and release on Christmas Island. All Tachardiaephagus species have a narrow host range and appear to be family specialists, known only to attack the Kerriidae, the family to which the yellow lac scale belongs (Table 3). Our initial studies indicate that (a) T. somervillei attacks T. aurantiaca across 1900‐km range in Peninsular Malaysia and Malaysian Borneo, (b) is the most abundant natural enemy of T. aurantiaca, (c) has a short life cycle compared to its host, (d) exhibits superparasitism (i.e., where multiple progeny emergence from a single host individual); (e) causes high rates of parasitism on T. aurantiaca in the presence of tending ants, including the yellow crazy ant, and (f) can be reared under laboratory conditions. Coccophagus ceroplastae and Encyrtus infelix, both parasitoids of a wide variety of coccid scale insects, are already present on Christmas Island. The three parasitoids T. somervillei. C. ceroplastae and E. infelix could be deployed in combination against the entire assemblage of honeydew‐producing scale insects in YCA supercolonies. Project 2b. Scale insect survey on Christmas Island (biology, host range, habitats, natural history, identification). No native or endemic scale insect species have been discovered in intensive and extensive searches for scale insect species on Christmas Island. However, 400 hours of search over two years did yield five additional exotic scale insect species previously unknown to the island. Assuming that any prospective biological control agent for Tachardina aurantiaca on Christmas Island would be a narrow family specialist (Kerriidae) and all known scale insect species are non‐ native and invasive, the probability of any direct non‐target effects is negligible. Project 2d. Genetic and morphological matching between Tachardina aurantiaca and Paratachardina pseudolobata on Christmas Island and Southeast Asia. The single population of T. aurantiaca on Christmas Island matches morphologically and genetically those populations examined so far within its native region in Southeast Asia. This establishes the identity of Tachardina aurantiaca on Christmas Island, making the successful establishment on Christmas Island of a biological control agent that attacks T. aurantiaca in its native range more likely. Further collections and analyses of T. aurantiaca in Eastern Malaysia (Sabah) and exploration in southern Thailand should establish if any morphological or genetic variation occurs across its native distribution in Southeast Asia. Project 2e. Scale population dynamics, especially the ecology of lac scale, Tachardina aurantiaca. The life cycle of Tachardina aurantiaca is relatively long for a scale insect but several overlapping generations occur in a single year. Female size is significantly correlated with fecundity, indicating that conditions that affect female size are likely to have a strong influence on population growth rates and density. The