Lymantria dispar (Linnaeus) is a widely distributed and very variable species, illustrated by the 57 names for synonyms, subspecies, races, forms and mutations recorded by Ferguson (1978). Needless to say, the classification of this species has been very much in flux. Goldschmidt (1940: 59) recognised seven subspecies based on scale colour of the abdomen tip in the female, female wing colour and size. To these, Inoue (1956, 1957) added two additional subspecies from Japan. In the most recent revision of the genus Lymantria by Schintlmeister (2004), Lymantria dispar is divided into only two subspecies, L. dispar dispar (Linnaeus) ranging from Europe across Asia to China, Korea and the Amur region, and L. dispar japonica (Motschulsky) from Japan. The two Japanese subspecies of L. dispar named by Inoue (1956) are treated by Schintlmeister (2004) as L. albescens postalba Inoue and L. albescens tsushimensis Inoue, subspecies of a different species. Lymantria dispar dispar has long been divided into two races, European Gypsy Moth and Asian Gypsy Moth (AGM), the former, with flightless females, accidentally introduced into North America in 1868 or 1869. Strictly speaking, the term Asian Gypsy Moth comprises only the mainland Asian population of L. dispar dispar from China to the Amur region, but the Japanese Gypsy Moth, L. dispar japonica, is often included under the term Asian Gypsy Moth. While the Japanese and mainland populations are two different subspecies, they both have females which are able to fly for long distances, in contrast to the European race of L. dispar dispar with flightless females with much smaller wings. Mitochondrial DNA variation among L. dispar populations (Bogdanowicz et al. 2000) resolved four groups, only partly concordant with the above scenario, representing moths from 1) Europe, Tunisia and North America, 2) mainland Asia and the Japanese Islands Honshu and Kyushu, 3) Hokkaido (Japan) and 4) Okinawa (Japan). The first population is concordant with the European Gypsy Moth whereas the complex distribution of the three populations from mainland Asian and Japan confirms the high genetic diversity of L. dispar in this region as indicated by the numerous earlier names below species level. It may also suggest that the use of the name Asian Gypsy Moth for the Asian as well as the Japanese populations is quite acceptable for practical reasons. Since the crucial diagnostic characters for this protocol are the genitalia structures which are indistinguishable between races and subspecies of L. dispar, the exact definition of AGM is irrelevant in this context.

Ferguson (1978) and Holloway (1999) provide descriptions, diagnoses and illustrations of the family Lymantriidae and the genus Lymantria. However, there are no clear-cut diagnostic characters for this large and very varied genus apart from general similarities in wing shape and pattern and the nature of the extensile female ovipositor. Schintlmeister (2004) divided Lymantria into 12 subgenera, with L. dispar the type species of the subgenus Porthetria Hübner which among other species includes L. lunata Stoll and the Australian L. antennata Walker and L. pelospila (Turner). Apart from a short ovipositor shared with the subgenus Papuatria Schintlmeister, the subgenus Porthetria is mostly characterised by wing pattern elements, in particular two prominent transverse median bands in the female, usually converging towards the dorsum. This generic subdivision, admittedly for pragmatic reasons rather than impelled by 'important' taxonomic differences (Schintlmeister 2004), will have to be confirmed with molecular studies. Lymantria is not only a very diverse, but also a very large genus with its 167 currently recognised species (Schintlmeister 2004) occurring mainly in the Oriental region. The subgenus Porthetria containing the AGM alone comprises 40 species. The fact that many Lymantria species are strongly sexually dimorphic in wing colour and pattern, with the females of a few flightless with reduced wings, further complicates identification.

The aim of this protocol is to provide unequivocal recognition of AGM, especially the usually heavily damaged specimens recovered from pheromone sticky traps. Genitalia, in particular those of the male, are the only structures allowing reliable Lymantria species identification. The first step of the key checks on the basis of external characters whether a suspect specimen is indeed a lymantriid moth, and if so, the key allows separation of AGM from Australian Lymantria species for both sexes on the basis of the genitalia.

Background

Brief historical background relating to detection and spread
Lymantriid moths are a group of major economic importance as defoliators of a wide variety of trees. A few are crop pests and many are also of medical significance as their larvae have urticating hairs which may cause severe irritation and even anaphylaxis. In Australia the family comprises just described 74 species in 19 genera, however the world fauna is estimated to contain 2,500 species. There is little expertise in Australia for identifying these species, and distinguishing those of quarantine importance from the others. Australia needs this capacity in order to be able to respond rapidly in the event of an incursion.

Gypsy moths (Lymantria dispar Linnaeus) are pests of forest and urban areas that periodically outbreak to very high population densities in parts of their range. They have been recorded from more than 650 species of plants, making their establishment highly likely if ever there is an incursion event, and making them extremely difficult to control. Indigenous populations of gypsy moths extend from continental Europe and the northwest coast of Africa through Asia to Japan. The European gypsy moth was intentionally introduced to Massachusetts, USA, from western Europe in the late 1860's by an amateur entomologist investigating the species' potential for silk production. A decade later the moth populations had reached defoliating levels in the area of their accidental release. The species spread rapidly through the eastern USA and Canada. The more vagile Asian gypsy moth established in the USA more recently.

It is estimated that the cost of controlling European gypsy moth alone in the USA is US$30 million per year.

Although the most economically important lymantriid species, gypsy moths are only one of more than 30 species of Lymantriidae that have been listed as threats under the Biosecurity Act of New Zealand. Six other species are of particularly high risk to forestry because of their pest status and polyphagous nature. These are the nun moth (L. monacha), pink or rose gypsy moth (L. mathura), vapourer or rusty tussock moth (Orgyia antiqua), white marked tussock moth (O. leucostigma), Douglas fir tussock moth (O. pseudotsugata) and white spotted tussock moth (O. thyellina). Their indiscriminate oviposition behaviour (they oviposit even on containers and ship superstructures) makes their arrival in Australia very likely. Life history strategies such as an especially long over-wintering phase in the egg stage, allow them to remain alive for long periods, enabling eggs to cross the equator and arrive in Australia in a viable state. It is therefore essential that Australia have the capacity to rapidly and accurately identify lymantriid moth adults, larvae and eggs that are intercepted by quarantine authorities.

There are two major factors complicating the identification of lymantriid moths. Firstly, few living taxonomists have specialised in this group and consequently few comprehensive taxonomic revisions exist for genera of Lymantriidae. There is currently only one full-time professional taxonomist in the world whose major focus is this family (Dr. Ugo Dall'Asta, Royal Museum for Central Africa, Tervuren, Belgium) however he has worked only on the fauna of sub-saharan Africa to date. Comprehensive treatises are generally not available, despite the obvious need, especially for Orgyia species. An exception is the recent revision of the world fauna of Lymantria by amateur lepidopterist Alexander Schintlmeister of Dresden, Germany. In addition, Dr. M. Pogue of the USDA Systematic Entomology Laboratory (Beltsville, Maryland, USA) and Dr. P. Schaefer (recently retired from the USDA) have completed a diagnostic manual for the economically important members of this genus. Lymantria is therefore the genus that is best known taxonomically and this is the obvious starting point for diagnostics training. Secondly, taxonomic works have tended to concentrate on the morphology of adult moths and diagnostic information is rarely available for the immature stages. In addition, as outlined above, incursion events are most likely to involve eggs laid on ships, however, their eggs have few morphological characters and no diagnostic characters have been identified. DNA diagnostics are therefore sorely needed. DNA barcoding shows tremendous promise for the identification of lymantriid species and the knowledge gained during the course of this diagnostic training is being applied to extending the published preliminary study of Ball & Armstrong (2006) to all important species of Lymantriidae.