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When should a non-aggressive exotic species be demoted to a harmless naturalized resident?

By Dr. Laurel Haavik, US Forest Service

Exotic species that establish, spread, and cause substantial damage are demonized as foreign invaders that charge with menacing force across the landscape. Rightly so; those pests threaten to displace or eliminate native species and alter ecosystem functions. Chestnut blight, emerald ash borer, and hemlock woolly adelgid are all excellent examples. What about invaders that aren’t so destructive? Or, at least don’t seem to be at the moment? At what point do we stop monitoring a seemingly innocuous invasive species, especially one that has proved itself a serious pest elsewhere? To make this decision, it’s helpful to know how much the species has affected its new habitat, and whether this impact already has or is likely to change over time. That is exactly what we set out to do with the European woodwasp, Sirex noctilio, in Ontario.

Nearly a decade after the woodwasp was first found in a trap near the Finger Lakes in New York (and then a year later across Lake Ontario in Sandbanks Provincial Park), it still hadn’t killed pines in noticeable numbers, either in the US or Canada. Native to Europe and Asia, this woodwasp has been introduced to several countries in the Southern Hemisphere, where it has been a serious pest in forests planted with exotic pines. By contrast, in North America, it seems that only the weakest trees, those that are already stressed by something else, are killed by the woodwasp. Would forests with many weakened trees allow populations of the woodwasp to build up enough that they could then kill healthy trees in well-maintained forests? Could we find any evidence that this had already happened or would likely happen in the future?

Our goal was to measure the impact the woodwasp has had in Ontario, and whether that has changed over time, by closely examining the same trees in pine forests every year. First, we had to find sites where the woodwasp could be found, which wasn’t every pine forest, and where landowners would allow us to work. We were not interested in sites that were well-managed, because research had already confirmed that the woodwasp was not present in those forests. We used records of positive woodwasp captures from the Ontario Ministry of Natural Resources trap survey as a guide. We visited 50 potential sites, and eventually selected eight for close scrutiny in our long-term study. These sites were areas where there was likely to be intense competition among trees for resources, with plenty of stressed trees for the woodwasp.

The European woodwasp was probably absent from a well-managed red pine forest (left), but likely to be found in an un-managed scots pine forest (right).

We visited all eight sites every fall from 2012 to 2016, after woodwasps had the opportunity to attack trees. Adult woodwasps mate and lay eggs, attacking trees in the process, in mid-summer. Attack was visible as distinctive resin beads scattered over the trunk. We recorded which trees had been attacked, and later (usually the following year) killed by the woodwasp.

The woodwasp population was considerable at some of our sites, having killed about one-third of the trees within five years. Though at other sites, the population was much smaller, having killed only a small percentage of trees. We’re not exactly sure what caused this variability. It’s possible that the woodwasp arrived at some of our sites years before it arrived at others, and the most vulnerable trees were long dead at the sites it invaded earlier. We have no record of time since woodwasp invasion at any of our sites. It’s also possible that local environmental conditions, which we did not measure, could in some way have affected tree resistance or the woodwasp population.

Most curious, though, was that over the five years many trees attacked by the woodwasp did not die – around 50 to 80%. At least half of these trees were attacked again and again in successive years. We had captured an interesting part of the woodwasp’s ecology, its way of essentially priming trees to become better habitat for its young. When laying eggs, female woodwasps also inject a self-made toxic venom along with a symbiotic fungus into the tree, to help kill it. If the tree is sufficiently resistant to attack, the female may not lay eggs, only the fungus and venom. The fungus and venom then work in concert to weaken (prime) the tree for re-attack – and hopefully successful colonization – in subsequent years.

Female woodwasps sometimes die while laying eggs. Survival of the fittest?

Two-thirds of trees that were attacked by the woodwasp at some point in our study (one or more times) did not die, which shows that most trees selected by the woodwasp as suitable habitat are at the moment resistant to its advances. This also shows, along with the variability in woodwasp impact among sites, that this invader is active in the forest. Should environmental conditions change (say, if a drought occurs), woodwasp populations could quickly rise to outbreak levels, which could kill large numbers of healthy pines. This has happened in other places.

Long-term study of these sites, and hopefully others, is needed so that we can be aware of changes that arise in woodwasp impact. This will allow us to be proactive about what steps to take to manage this invader, should it become a problem. It will also help us better understand and predict what causes exotic species to vacillate on the spectrum between aggressive invader and innocuous resident.

Want to read more? Check out the original article published in The Canadian Entomologist, which is freely available for reading & download until May 14, 2018.

Haavik, L.J., Dodds, K.J. & Allison, J.D. (2018) Sirex noctilio (Hymenoptera: Siricidae) in Ontario (Canada) pine forests: observations over five years. The Canadian Entomologist, 1–14. doi: 10.4039/tce.2018.18

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Hymenoptera at Sunset

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Last night I went for a ramble at Iona Beach in Richmond BC, looking for insects and inspiration in the sand dunes. I knew the sunset would be pretty, as there was a bit of light wispy cloud in the west, so I hurried out to the end of the beach where restoration efforts hadn’t ripped up the ground.

I found my subjects attaching themselves to twigs and vegetation, bedding down for the night.

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Coelioxys spp. (Megachilidae) preparing to attach to a dead, dried flowerhead. Next time you go for a sunset beach stroll, have a look for these and other sleeping insects!

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If you are a photographer, the combination of the setting sun and your flash can do wonderful things to highlight your subjects.

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An Ammophila wasp (Sphecidae), shot without flash, is but a silhouette against the darkening sky.

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I am not sure, but I think I may have gone overboard with this session! It seems like it could be an ad for a tropical beach vacation for insects.

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This slender and elegant caterpillar hunter is fast and nervous in the day, but wonderfully calm in the evening.

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As the light was failing, so were my flash batteries, but this unplanned blur of a cluster of male Colletes males is still cool!

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There are so many bees on this flower that it sags to the ground!

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The Colletes cluster against the darkening sky of night.

Next time you go for an evening stroll on a sandy beach, head up to the dune vegetation, and have a look for these wonderful sleeping wasps and bees!

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Canadian amber reveals bizarre ants from the Cretaceous – Editor’s Pick for TCE 145(4)

By Dr. Chris Buddle, McGill University & Editor of The Canadian Entomologist

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It’s with great pleasure that I announce my pick for the latest issue of The Canadian Entomologist.  Ryan McKellar and colleagues wrote a paper on a new trap-jawed ant from Canadian late Cretaceous amber (freely available during September).  As they write in the Abstract, the new species “….expands the distribution of the bizarre, exclusively Cretaceous, trap-jawed Haidomyrmecini beyond their previous records…”. They truly are bizarre! Facial structures right out of a sci-fi movie!  When reading the paper, I was also surprised that the fossil record for the Formicidae is sparse during the Cretaceous.

Haidoterminus cippus. Figure 1 from McKellar et al. 2013

I asked the lead author a few questions about this work, and am pleased to share the responses with you. It’s truly exciting research, and I am thrilled that the pages of TCE include systematics from amber. This work stirs the imagination, and takes us all back in time.

What inspired this work?

My interest in the Canadian amber assemblage really began when Brian Chatterton (then my M.Sc. supervisor) showed me some of the slides that he had borrowed from the Royal Tyrrell Museum of Paleontology in order to write a book on Canadian palaeontology. The sample set contained insects with bizarre adaptations for life at low Reynolds numbers, and obvious ecological associations, spurring an interest that ultimately led to a research in parasitic microhymenoptera. Michael Engel subsequently introduced me to a much wider array of taxa, and we continue to explore the Canadian assemblage together and with the help of colleagues.

What do you hope will be the lasting impact of this paper?

New records, such as this trap-jawed ant, help to flesh out our picture of the amber-producing forest and its inhabitants. I hope that a comprehensive account of this assemblage will eventually provide insights into terrestrial conditions that are unavailable from other fossil types, and that this will shed some light on changes in diversity and conditions leading up to the end-Cretaceous mass extinction.

Where will your next line of research on this topic take you?  

With any luck, we will be able to complete our coverage of Hymenoptera in Canadian amber soon, and make more of a concerted effort to cover other insect orders and some of the ecological associations found within the deposit. Grassy Lake amber still has a lot to offer, but it is only one of western Canada’s many amber deposits. As a larger-scale project, we are currently part of a team examining the numerous fragile ambers associated with coals in the region. The goal of this research is to create an amber-based record of forest types and inhabitants that spans more than 10 million years within the Late Cretaceous and Paleocene.

Can you share any interesting anecdotes from this research?

Surface-collecting amber can be quite difficult, because unpolished Canadian amber typically has a matte orange-brown colour, and is often covered with a carbon film or weathering crust. If there is no fractured surface visible and the specimen is not translucent, it can be quite difficult to distinguish from the surrounding coal or shale. Furthermore, there is such a range of shapes and sizes that some of the smaller amber droplets are easily confused with modern seeds. One of the quickest ways to see if you are dealing with amber is to wet the specimen and look for amber’s characteristic lustre, or tap the specimen on your teeth (amber feels like plastic compared to most suspect rocks). Naturally, I have licked quite a few samples in the course of my collecting, and have lost a lot of my appreciation for rabbits.

A selection of amber from Grassy Lake. Photo courtesy Brian Chatterton

A selection of amber from Grassy Lake. Photo courtesy Brian Chatterton

Thanks to Cambridge Journals Online for making this month’s Editor’s Pick Freely Available for the month of September!

This post is a regular series highlighting great papers from the pages of the Canadian Entomologist. 
McKellar R.C., Glasier J.R.N. & Engel M.S. (2013). A new trap-jawed ant (Hymenoptera: Formicidae: Haidomyrmecini) from Canadian Late Cretaceous amber, The Canadian Entomologist, 145 (04) 454-465. DOI:

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Editor’s Pick: Resins, exotic woodwasps and how a study species picks a researcher.

by Christopher Buddle, McGill University

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As the Editor-in-Chief of The Canadian Entomologist, I have the pleasure of seeing all papers move through the publication process, from first submission to approval of the final proof.  This places me in a position to fully appreciate the incredible entomological research occurring around the world.  As one way to promote some of the great papers within TCE, I have decided to start a series of blog posts titled “Editor’s Pick” – these are papers that stand out as being high quality research, and research that has broad interest to the entomological community.  I will pick one paper from each issue, and write a short piece to profile the paper.

For the first issue of the current volume (145), I’ve picked the paper by Kathleen Ryan and colleagues, titled “Seasonal occurrence and spatial distribution of resinosis, a symptom of Sirex noctilio (Hymenoptera: Siricidae) injury, on boles of Pinus sylvestris (Pinaceae)“.   Sirex noctilio is a recently introduced species in Canada, and is a woodwasp that we need to pay attention to.   As Kathleen writes, “unlike our native species of woodwasps, it attacks and kills living pines” and because of this, we must strive to find effective ways to monitor the species.  One potential approach is to look for signs of resinosis, or ‘excessive’ outflow of tree sap and resins from conifers.  The goal of this work was to specifically assess “the spatial and temporal distribution of resin symptoms of attack to optimise sampling“.  The work involved Kathleen spending a LOT of time in the field, observing evidence of damage to trees, and assessing timing of resinosis relative to other damage to pine trees as related to woodwasps.  In the end, Kathleen was able to confirm that in most infested trees, the appearance of resin was a meaningful detection method.  This is a very practical paper, and very useful towards finding the best methods to detect this exotic species.

Sirex noctilio female - Photo by K. Ryan

Sirex noctilio female – Photo by K. Ryan

I asked Kathleen a few questions about this paper and the context of the work.

Q: Kathleen, what first got you interested in this area of research?

A: I became interested in studying Sirex’s interaction with other subcortical insects. Sirex was recently detected in North America at the time and we didn’t know much about it here including how, where and when to find it  – all of which were essential in planning research about insect interactions. So this study was my starting point – my “getting to know Sirex” study.

Q:  What do you hope will be the lasting impact of this paper?

A: This paper is the result of the many hours of field observations that helped me to become more familiar with Sirex. Since its really basic research, I hope that this paper might be a useful starting point for other people beginning to work with Sirex.

Q:  Where will your next line of research on this topic take you?  

A: Currently, I’m studying another invasive wood-borer, but I’d like to work with Sirex again – it’s a really interesting and unique insect biologically and ecologically. I’m especially interested in studying Sirex community ecology in its native, European, range to see how it compares to North America.

This is truly an important area of study, and I do look forward to seeing more of Kathleen’s papers in TCE.

Finally, I asked Kathleen about any amusing anecdotes about the research, and she shared this wonderful story with me:

The first day we worked together, my PhD advisor Peter de Groot, dropped me off at a forest site with instructions to only observe and collect absolutely no data. I had been in the forest for only a few moments, when a female Sirex landed right in front of me. So being an entomologist, naturally I caught her. A couple of hours later, still holding her, I met back up with Peter and sheepishly admitted that I had caught some “data”. Thinking it fantastic, from that point forward he told everyone that Sirex had picked me as her project.

Looking for wood wasps - Photo by K. Ryan

Looking for woodwasps – Photo by K. Ryan

I believe that these kinds of stories behind the research make Entomology more accessible and real, and help us appreciate the human element of scientific research.

As a final note, the entomological community was very saddened by Peter de Groot’s death in 2010.  His legacy to Canadian Entomology is still very strong.

A special thanks to Kathleen for answering a few questions, and sharing insights into the first ‘Editor’s pick’ for The Canadian Entomologist

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Reference:  Ryan, K, P. de Groot, S.M. Smith and J. J. Turgeon.  Seasonal occurrence and spatial distribution of resinosis, a symptom of Sirex noctilio (Hymenoptera: Siricidae) injury on boles of Pinus sylvestris (Pinaceae). The Canadian Entomologist 145: 117-122. Link.

Female of Polistes parametricus Buck Vespidae Wasp
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Taxonomic adventures in the world of paper wasps (Polistes, Vespidae)

By Matthias Buck, Royal Alberta Museum, Edmonton

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For many of us who are working as taxonomists, describing new species has become somewhat of a routine. Sometimes it can even become a burdensome chore: I am thinking about those of us who work on hyperdiverse groups of insects in the tropics where almost every species is undescribed (case in point: one of my former lab mates recently described 170 new species of a single genus of Diptera in one paper!). However, the feeling is very different when new species unexpectedly show up in iconic groups that were thought to be well-known. Suddenly, common and familiar creatures turn into an exciting new research frontier, providing a fresh rush of adrenaline!

Mug shot of a female of Polistes hirsuticornis Buck. Vespidae Wasp

Mug shot of a female of Polistes hirsuticornis Buck. The hairs on the basal articles of the flagellum are longer than in related species (Photo credit D.K.B. Cheung & M. Buck).

This is what happened a few years ago when I started working on the vespids of the northeast. The family Vespidae (which includes mason wasps, paper wasps, yellowjackets and hornets) is most diverse in warmer parts of the World, as is the majority of stinging wasps. Doing a review of the northeastern Nearctic fauna therefore didn’t seem to be a very promising project for taxonomic novelty. Especially considering that the fauna of the eastern half of the continent is significantly less diverse and far better known than that of the west.

To my utmost surprise the study (published 2008 in the Canadian Journal of Arthropod Identification) not only turned up four new species of mason wasps but also two new paper wasps (Polistes). As you know, paper wasps are some of the most iconic species in the world of wasps, almost as much as their odious relatives, the yellowjackets. Further to that, they have received great attention as model organisms for the study of social behaviour and its evolution in insects. Finding not only one, but two new species in a group like this was beyond what I expected in my wildest dreams.

So how did it come to pass? As a novice to paper wasps I expected that reviewing the taxonomy of such a high-profile group would be like a walk in the park. Weren’t there scores of scientists before me who seemingly had no difficulties in identifying these sizeable and handsome insects for their behavioral studies, filling up cabinets of specimens in collections across the continent? Or so I thought! After months of fruitless staring through the microscope my nonchalant attitude gradually turned into frustration. One of the species, the common and widespread Northern Paper Wasp (Polistes fuscatus), was so variable that it blended virtually into almost every other species in the same subgenus. Previously published keys gave me a pretty clear sense of what typical specimens of each species look like, but where were the objective criteria that would allow me to identify the numerous intermediate forms? Truly, I found myself in a taxonomic quagmire!

Aedeagus of Polistes parametricus Buck. Vespidae Wasp

Aedeagus (penis) of Polistes parametricus Buck. The size, shape and position of teeth is diagnostic with regard to P. fuscatus and P. metricus, with which this species was previously confused (Photo credit D.K.B. Cheung & M. Buck).

Grasping for straws I turned to three taxonomic methods that had not been applied to Polistes before: DNA barcoding, detailed study of male genitalic features and morphometric analysis. During the previous months, I had rounded up a number of puzzling specimens which represented the spearhead of my taxonomic headaches, and submitted them for sequencing. The results came back like a thunderclap, turning my anguish into cautious excitement: the DNA barcodes of these troublemakerswere clearly different from any of the described species. With renewed energy I launched into a detailed morphological study which led to the discovery of several new diagnostic characters, confirming the distinctness of these wasps beyond a doubt. A lot of hard work had finally paid off, and I was looking at the first newly discovered species of paper wasps in eastern North America since 1836 when Amédée Louis Michel Lepeletier de Saint-Fargeau described Polistes rubiginosus!

Female of Polistes parametricus Buck Vespidae Wasp

Female of Polistes parametricus Buck nectaring on goldenrod in West Virginia (Photo credit: Donna Race).

Since molecular methods, and in particular DNA barcoding, have received a lot of attention in recent years, it seems opportune to share some of my experiences working on Polistes. Unlike a few other taxa (such as spider wasps, Pompilidae), vespids sequence nicely and easily from pinned specimens, which makes them an ideal group for this kind of study. I found the sequence data extremely helpful but they certainly did not provide the cure of all taxonomic confusion. Barcoding uncovered an unexpected genetic diversity below the species level, which proved to be hard to interpret in the absence of other data. In Polistes there is no hint of a “barcoding gap”, which postulates that genetic distances between individuals of the same species are (nearly) always greater than those between conspecific individuals. In fact, some of the species were genetically so similar that they differed by a mere 2 base pairs (out of 658). Nonetheless, the combination of molecular data with fine-scale morphology resulted in a quantum leap forward for Polistes taxonomy. Just days ago, I found out that a group of researchers in Germany and Switzerland are making similar progress on European paper wasps using a nearly identical approach.

My research paper on eastern Nearctic Polistes, including formal descriptions of Polistes hirsuticornis Buck and P. parametricus Buck, was published in the journal Zootaxa on October 1st.
Matthias Buck, Tyler P. Cobb, Julie K. Stahlhut, & Robert H. Hanner (2012). Unravelling cryptic species diversity in eastern Nearctic paper wasps, Polistes (Fuscopolistes), using male genitalia, morphometrics and DNA barcoding, with descriptions of two new species (Hymenoptera: Vespidae) Zootaxa, 3502, 1-48 Other: urn:lsid:zoobank.org:pub:6126D769-A131-49DD-B07F-0386E62FF5B9

Dufourea bee on flower
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CJAI #20 – Dufourea (Apoidea: Halictidae) of Canada

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By Sheila Dumesh, entomology research assistant at York University.

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My interest in bees was ignited in 2007, when I took a biodiversity course in my last year as an undergraduate student at York University in Toronto.  The course instructor was the well-known melittologist, Laurence Packer, and, although I had not met him before, I had heard many good things.  Laurence’s affection for bees was inspiring, not only to me, but to others in the past and many more to come.  He was so fascinated by these cute and fuzzy insects (at the time, I did not see myself describing them as such).  Even though he had been studying bees for decades, the look of excitement on his face never faded when collected and examined them.  Back then, my knowledge of bees was very limited.  I was unaware of their diversity, importance, and great beauty!

I began with an Honours thesis under Laurence’s supervision in the “bee lab” at York University.  I was keen on taxonomy and began a systematic study on a Central American bee genus, Mexalictus.  For my Master’s thesis, I chose to continue that work and complete a revision of Mexalictus, which included descriptions for 20 new species, an illustrated key, and a phylogenetic analysis.  I conducted my field work in Costa Rica, Guatemala, and Mexico, where I sampled in high elevation cloud forests (the known habitat of Mexalictus).  As these species are quite rare, I did not always have the pleasure of finding them; although this was somewhat upsetting, I was amazed by the bee (and general insect) diversity in that part of the world.  I was aware of it, but being out in the field in those countries was a truly amazing experience.  Just the change in habitat and species make-up along a small sector of the elevation gradient was incredible to witness!

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Dufourea sp. – Photo by Sheila Dumesh

Throughout my time as a Master’s student, I studied other groups of bees and collaborated with others in our lab.  One such project is the revision of the Canadian species in the genus Dufourea (Apoidea: Halictidae), which I undertook with Cory Sheffield and recently published in the Canadian Journal of Arthropod Identification.  There are eight species in Canada, but some were described from only one sex, the descriptions were written by several authors in different publications, and a key to identify these species was previously unavailable!  These bees are also floral specialists, meaning they visit specific flowers (usually a genus or family).  Cory and I set out to revise this group and provide all of this information in one paper.  The identification key is user-friendly and illustrates the characters mentioned in the key couplets to aid the user.  We also constructed species pages, which include full descriptions, important features, distribution maps, and images of each species.

We are striving towards creating many more illustrated (and web-based) keys to facilitate bee identification.  I am very excited to have this work freely available and hope that it is found useful by others in the community!

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Dumesh, S. & Sheffield, C.S. (2012). Bees of the Genus Dufourea Lepeletier (Hymenoptera: Halictidae: Rophitinae) of Canada, Canadian Journal of Arthropod Identification, 20 DOI: 10.3752/cjai.2012.20