Wasp Identification Australia
Lynn Hepler
Sphex corporosus (left) and Sphex flammeus (right). Photos by Thorleif Drfel, Museum fr Naturkunde, CC-BY 4.0.
After being mostly neglected for more than a hundred years, a group of digger wasps from Australia has been given a major overhaul in terms of species descriptions and identification methods. This approach has led to an almost 50% rise in the number of recognized species of these wasps on the continent. The study was published in the open access journal ZooKeys.
More than a century has passed since the last revision of this group in the Down Under. Using pinned, dried individuals from museum collections all over the world, Drfel and Ohl inspected more than 900 specimens and recorded the morphological characters that they deemed most useful for species differentiation.
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Wasp sting fatalities have rarely been reported in Australia. We useddata from the Australian Bureau of Statistics and State coronialauthorities to investigate deaths from wasp stings in Australia from1979 through 1998. Seven cases were identified, all involving men inrural settings. Five of the seven victims had prior histories of waspor bee venom allergy, or both, but none carried injectable adrenalin.All patients with a history of systemic Hymenoptera sting allergyshould undergo assessment for immunotherapy and carry adrenalin.
Despite the importance of fatalities from Hymenoptera stingsinternationally, little has been published on the circumstances andincidence of such deaths in Australia. For example, an analysis ofAustralian bee sting fatalities during 1960-1981 was unable toobtain adequate clinical information about most of the fatalitiesduring that period, and coronial records were examined for only one ofthe 27 fatalities identified in that study.2 Despite the increasingabundance of the introduced and aggressive European wasp (V.germanica),6 and consequent concernsabout the increasing health risks posed by this vespid,3 even lessinformation is available about fatalities from wasp stings inAustralia than for those from bee stings. Indeed, only two minimallydocumented reports of fatal wasp stings exist in the Australianmedical literature. In 1913, Cleland noted "oedema of the larynx andsubsequent death occurred from a man being stung by a wasp. He had beendrinking out of the spout of a waterbag in which the wasp washiding".7 Lee also made reference to afatal wasp sting in a 47-year-old man in southern Queensland in1957.8
Analysis of fatalities can provide important information on thedeterminants of severe morbidity, which may be useful in injuryprevention. Thus, we investigated, in detail, wasp sting relatedfatalities that occurred in Australia over the past two decades. Thisperiod was coincident with the arrival and dispersal of V.germanica on the Australian mainland.6 In the absence of nationalcoronial data for this period, we used State-based coronialinformation systems. In particular, we aimed to identify thecontribution of allergy versus venom toxicity (envenomation), andthe likely contribution of V. germanica to the mortalityburden.
The seven fatalities identified during the 20-year periodcorrespond to a mean annual incidence rate of 0.02 deaths per millionpopulation per year. The deceased were all men living in northern NewSouth Wales, or in Queensland (from the southeast to the far northcoast). They were aged between 39 and 73 years (mean age, 54 years).Five of the seven deaths occurred during December and February, andthe remaining two deaths occurred in April and May. In no year was theremore than one death from wasp sting. All stings occurred in rural areasand four of the deceased were described as farmers in the coronialreports. The details of each case are summarised in Box 1.
In Europe4,10 and the UnitedStates,11 relative proportions ofdeaths from wasp and bee stings are different from those in Australia.In Sweden, these proportions are 90% for wasps and 10% forbees;4 corresponding figures forDenmark are 63% for wasps and 37% for bees,10 while, in the US, wasp andbee sting fatalities occur with approximately equalfrequency.11 By contrast, our findingof a wasp sting fatality rate of 0.02 per million population per year isonly a quarter of the reported Australian bee sting fatality rate of0.086 per million population per year.2 This may reflect therelatively recent arrival in Australia of the Europeanwasp6compared with the European honey bee.
Although our study was precipitated by concern about the healthimpact of European wasps, and we looked at a period that coincided withtheir arrival and spread on the mainland, we identified no fatalitiesattributable to this wasp. All of the wasp-sting deaths occurredoutside the known range of V. germanica.6 This may changeas increasing numbers of people become sensitised to its venom.Further research is required to ascertain whether the arrival ofV. germanica has altered sting-related morbidity patternsin Australia.
As in previous studies,2,4,10 in the deaths weexamined we found that the reponsible wasp was rarely formallyidentified. Nonetheless, it seems likely that at least one case wasattributable to a Polistes species. This is consistent withreports of severe allergic reactions to stings by Polistesand Ropalidia species in Queensland.12 Moreover, given thedistribution of the various vespid wasps,9 it seems likely that allseven fatalities were caused by Polistes andRopalidia species. This adds impetus to the call for purifiedRopalidia venom to become available forimmunotherapy,12 as, currently, onlyimported Polistes and Vespula venoms are available.
The absence of wasp sting mortality outside Queensland and NSWcontrasts with the nationwide occurrence of deaths from beestings.2 It is possible that the waspspecies found in Queensland and NSW possess greater allergenicpotential than those found elsewhere in Australia. No systematicresearch has yet been undertaken on this question. The formalidentification of the wasp species implicated in future fatalitieswould facilitate such research.
Consistent with previous analyses of bee and wasp sting mortalityinternationally,2,4,5 we found a low number ofstings, rapid onset of symptoms, no child fatalities andover-representation of middle-aged men among those who died. It hasbeen proposed that pre-existing heart disease might explain theincreased risk for men aged over 40 years;2,4 certainly, this may havecontributed to death in two of our cases. However, our findings differfrom these other reports in the high frequency of autopsyexaminations and low rates of underlying cardiorespiratorydisease.
Venom toxicity is rarely reported in Hymenoptera-relatedfatalities,2,4,10,11 and we found nofatal massive envenomations. In all cases death was attributable toanaphylaxis (although ideally mast cell tryptase and IgE levelmeasurements should be made to confirm this diagnosis). In contrastwith previous international reports, most of the victims in our studyhad either previously diagnosed allergy to wasp stings or a clearhistory of systemic reactions indicating severe allergy. Thus, mostof these deaths might have been prevented by specific immunotherapy,early treatment with adrenalin or both. However, patients and theirfamilies should be aware that vulnerability to venom-inducedanaphylaxis persists at least until maintenance doses ofimmunotherapy are attained.
As with Australian bee sting fatalities,2 most deaths occurred in thesummer months when human-wasp interaction is most likely. The ruralsetting of these fatalities highlights concerns about the acuteshortage of specialist allergists and clinical immunologists inrural areas,13 although it is unclearwhether such shortages contributed to the fatal outcomes.Nevertheless, this underservicing, combined with the lack ofRopalidia,12Myrmecia1 and other venoms forimmunotherapy, increases the importance of anaphylaxis emergencykits and education14 for those withlife-threatening allergy to insect stings and their families.
The fact that most of the deceased were reported to be farmers isconsistent with the fact that rates of work-related deaths inagriculture are among the highest in Australia.15 Informationon bites and stings should therefore be incorporated within injuryprevention programs such as those developed by FarmsafeAustralia.15
As noted in previous investigations of bee stingmortality,2 dependence on a single dataset is likely to lead to an underestimation of the total injury burden.It is possible that additional wasp sting deaths occurred during thestudy period but were not recorded because of miscertification,misattribution as bee sting, or other inadequate or inaccuraterecording. We found that the wasp sting diagnosis was almost whollydependent on the presence of a witness and absence of retained beesting on autopsy. Clearly, unwitnessed wasp sting deaths could beattributed to other causes, and our findings should be considered anunderestimate of wasp sting mortality.
The Situation: Since 1850, eucalyptus trees of >90 species have been imported as seed from Australia into California for a wide range of ornamental and other uses. Eucalyptus are now an ubiquitous plant in urban areas in southern California, and these plants are becoming increasingly more common in California's natural areas too where some species are considered to be invasive weeds. In urban areas, these native Australian trees are valued for their fast growth and tolerance of poor soils and drought. Consequently, eucalyptus is considered by many a valuable landscape, shade, and windbreak tree. For more than a century, these species remained virtually pest free. However, beginning in the 1980s, a series of eucalyptus-feeding insects invaded the region, beginning with the borer Phoracantha semipunctata (Coleoptera: Cerambycidae), which was first detected in California in 1984. Since then about 15 other species of eucalypt herbivores have invaded California, includin
g another Phoracantha species(in 1995), the leaf feeding weevil Australian Gum Tree Weevil (in 1994), the chrysomelid leaf beetle Trachymela sloanei (in 1998), and at least six species of psyllids, including the blue gum psyllid (Ctenarytaina eucalypti) and two lerp physllids (Glycaspsis brimblecombei and Eucalyptolyma maideni).