A race against pine: Wood-boring wasp in North America threatened by a Eurasian invader

Invasive species have diverse impacts in different locations, including biodiversity loss, as a result of native species being outcompeted for similar resources. A U.S. research team, led by Dr. Ann Hajek, Cornell University, studied the case of an aggressive Eurasian woodwasp that has recently established in North America and poses a threat to a native species. Their study is published in the open-access journal NeoBiota.

Most woodwasps play an essential part in the forest ecosystem, as they decompose wood, preferring dying or felled trees. They do so by laying their eggs in the wood underneath the tree bark. Curiously, the wasps also deposit a symbiotic fungus and venom that shuts down the tree’s defenses. As the tree weakens, the fungal infestation begins and the the tree starts to rot. When the eggs hatch, the larvae feed on the rotten wood before they emerge. This relationship is called obligate since the survival of the wasp is impossible without the fungal infestation.

IMG_2322Originating from Eurasia, the presence of the invasive species is dangerous because it can kill healthier pines. It has long been established in the southern hemisphere causing economic issues due to its attacks on pines. While pines have been introduced to that part of the world, they are native to North America, where the invasive wasp could be far more devastating.

Now that the invasive woodwasp has already been identified in the States, the scientists seek to find a way to protect its frail competitor, reporting a rapid decline in the North American species.

“We would often observe both species emerging from the same infested pine trees, but the ratios changed with time,” explains Dr. Ann Hajek.

“Shortly after the invasive colonizes an area, the native wasps emerging from the trees would equal the invasive. However, a few years later, the natives started to get fewer and fewer.”

It turned out that the Eurasian woodwasp has larger venom glands and produces more eggs, thanks to its greater body size. Furthermore, it emerges earlier than the North American species, so that it can find and colonize the most suitable trees first. By the time the native species lays its eggs, the authors speculate, most of the preferred trees are already occupied by the invasive, leaving a reduced supply of habitat for the newcomer’s larvae.

“Woodwasps are difficult to study and their biologies are generally poorly understood,” note the authors. “While the native species appears to be outcompeted from pines that both species prefer, it is possible that populations of the native can be sustained in trees less desirable to the invasive or unavailable during the time and place that the invasive is present.”

The scientists call for additional research on the native woodwasp in southeastern pine forests in USA, before the invaders spread to that area with extensive pine forests.

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Original source:

Hajek AE, Henry JC, Standley CR, Foelker CJ (2017) Comparing functional traits and abundance of invasive versus native woodwasps. NeoBiota 36: 39-55. https://doi.org/10.3897/neobiota.36.14953

Scientist collects 30 sawfly species not previously reported from Arkansas

Sawflies and wood wasps form a group of insects that feed mainly on plants when immature. Field work by Dr. Michael Skvarla, which was conducted during his Ph.D. research at the University of Arkansas, Fayetteville, USA, has uncovered 30 species of these plant-feeding wasps that were previously unknown in the state. The study is published it in the open access journal Biodiversity Data Journal.

After collecting sawflies in tent-like Malaise traps or hanging funnel traps, Dr. Michael Skvarla sent the specimens to retired sawfly expert Dr. David Smith for identification.

In total, 47 species were collected, 30 of which had not been found in Arkansas before. While many of the species are widespread in eastern North America, eight species were known only from areas hundreds of kilometers away.

“I knew that many insect groups had not yet been surveyed in Arkansas, but I was surprised that 66% of the sawfly species we found were new to the state,” Skvarla says.Fig 2 - Acordulecera dorsalis

“In addition, over a quarter of the newly recorded species represent large range extensions of hundreds of miles; Monophadnoides conspiculatus, for instance, was previously known only from the Appalachian Mountains. This work highlights how much basic natural history is left to discover about insects.”

Sawflies and wood wasps comprise the wasp suborder Symphyta and derive their common names from the serrated or saw-shaped ovipositor many species use to lay eggs into plant tissue, and because some species bore into wood.

While some sawfly and woodwasp species can be pests on crops or ornamental plants, most do not pose an economic concern, and all are harmless to people.

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Original source:

Skvarla M, Smith D, Fisher D, Dowling A (2016) Terrestrial arthropods of Steel Creek, Buffalo National River, Arkansas. II. Sawflies (Insecta: Hymenoptera: “Symphyta”). Biodiversity Data Journal 4: e8830. doi: 10.3897/BDJ.4.e8830

Flickr and a citizen science website help in recording a sawfly species range expansion

Social network Flickr and citizen science website BugGuide have helped scientists to expand the known range of a rarely collected parasitic woodwasp, native to the eastern United States. Partially thanks to the two online photograph platforms, now the species’ distribution now stretches hundreds of miles west of previous records. Previously known from only 50 specimens mainly from the Northeast, now the species was discovered in the Ozark Mountains by researchers from the University of Arkansas. Their study is published it in the open access journal Biodiversity Data Journal.

Spurred on by the find, Michael Skvarla, a Ph.D. candidate at the university, contacted retired sawfly expert David Smith who alerted him to a hundred unpublished specimens housed in the United States National Entomology Collection at the Smithsonian, many of which were collected as bycatch in surveys that targeted invasive species like emerald ash borer andAsian longhorned beetle. Additional specimens from Iowa, Minnesota, and Manitoba, which also represent significant western range expansions, were found after users posted photos of the species on the social network Flickr and the citizen science website BugGuide.

“We used two resources – photos on social media and bycatch from large trapping surveys – which are often underutilized and I was really happy we could work both of them into the paper,” said Skvarla, the lead author. “This work highlights their utility, as well as the importance of maintaining biological collections like the U.S. National Collection and continuing to collect in undersampled regions like the Ozark Mountains.”

Parasitic woodwasps attack the immature stages of longhorned beetles, jewel beetles, and other woodwasps which bore into wood and have long fascinated entomologists because of this parasitoid nature, which is unique among woodwasps, and rarity in collections. The Arkansas specimens, which belong to the species Orussus minutus and motivated the initial research into the group, were collected as part of a larger survey of the insect fauna around the Buffalo National River.

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Original Source:

Skvarla, M.J., Tripodi, A., Szalanski, A., Dowling, A.P.G. 2015. New records of Orussus minutusMiddlekauff, 1983 (Hymenoptera: Orussidae) represent a significant western range expansion. Biodiversity Data Journal, 3: e35793. doi: 10.3897/BDJ.3.e5793