After a great deal of perseverance and skill, Quentin Paynter and his team have managed to pull off one of the scientific highlights of 2014.
The Honshu white admiral butterfly (Limenitis glorifica), a native to Japan, has the potential to help control Japanese honeysuckle (Lonicera japonica), a serious up and coming environmental weed in New Zealand. The Environmental Protection Authority approved the release of the butterfly in August 2013, but attempts that spring to mass-rear and release it failed.
The project has stalled several times due to unforeseen problems such as the 2011 Japanese tsunami, which wiped out study and collection sites and prevented travel to Japan for a year, but the main problem with this agent has been trying to get the butterflies to mate in captivity. “They have an elaborate courtship display where the male circles around the female and they need plenty of space to do this,” explained Quent. The white admirals failed to breed at Butterfly Creek, which is a relatively spacious butterfly house in Auckland. Previously we had flown in the ‘master-mater’, Professor Bob Platt from the USA, to try to hand-pair the butterflies, but that didn’t work either.
In a final attempt to establish the butterflies, Quent and his colleague Chris Winks planned another trip back to Japan in September last year. The idea was to catch wild females (the assumption being that they had already mated) and collect fertile eggs from them, bring this material back to New Zealand and eventually directly field-release the resulting new adults. “We hoped that if we released newly-emerged adults into suitable natural conditions in spring they would mate and reproduce,” said Quent. “It was the only remaining viable option left to us,” he added. It meant keeping the imported material in containment in New Zealand until we were sure it was safe to release it. We needed to double-check we had the right species (there is another similar species in Japan with a wider host range), and ensure it was free of disease.
With Japan and New Zealand being in different hemispheres, there was also a seasonal timing issue to overcome. We had to attempt to collect butterflies or eggs as late as possible in Japan and slow development down so the new adults would not emerge too early, before temperatures had warmed up sufficiently. “We knew that the white admiral normally has three generations a year in Japan, but because we had never visited in autumn before we weren’t sure exactly when, or at which sites, the third generation would be present, so we booked flights to stay in Japan for the first three weeks of September, to give us the best chance of our trip coinciding with the white admiral flight period,” Quent said.
“This proved to be a wise decision, because after the first 10 days or so we had virtually nothing to show for our efforts in the field. We did, however, visit Dr Hideshi Naka at Tottori University, who showed us his technique for hand-pairing butterflies, which differed from techniques we unsuccessfully attempted with Bob Platt. However, Dr Naka’s technique was very fiddly, but it did represent another ‘if all else fails’ option,” added Quent.
After unsuccessfully visiting numerous sites that had yielded many eggs on previous trips, Quent and Chris found a large patch of Japanese honeysuckle in riverine forest near Utsonomiya where they were able to collect eggs and a few adult females, which laid further fertile eggs. The key thing now was to ensure that the emerging larvae did not enter their usual overwintering diapause. We kept the caterpillars relatively cool, but at a long day length, so that they continued to develop slowly, and fortunately this strategy worked perfectly.
In theory an insect can become established through releasing just one male and female, but historical data tell us that establishment success is related to the numbers released and that small releases usually fail. “Although pleased with our efforts, we still had relatively few eggs and larvae (especially considering a minimum of 30 would need to be sacrificed for disease-testing) and time was rapidly running out. But to our great relief we managed to collect three more adult females and a good haul of eggs on our penultimate day in Japan,” explained Quent.
On return to New Zealand the female butterflies were fed on a diet of Pokari Sweat (a Japanese sports drink that Japanese entomologists claim has everything a butterfly needs!) and they began ovipositing soon after being installed in the Beever Containment Facility in Auckland; producing dozens of fresh eggs. After several days the team breathed a huge sigh of relief when the eggs proved to be fertile and larvae emerged – and another big sigh of relief when subsequent disease-testing indicated that the caterpillars were healthy. However, we soon had a new problem: the caterpillars appeared to be developing too quickly when the weather was still too cold. Again we turned the temperature down to slow development, but nevertheless the first adults still emerged in mid-October – rather earlier than hoped.
Once the new adults had emerged, and with permission to take them out of containment granted, the adults were released at a site in the Waikato and another in Auckland. Adults were released over a 2-month period as new butterflies emerged, with the first release of 27 adults occurring at the end of October and the “lucky last” being released in early December. A total of 178 were released at the Waikato site and 56 in Auckland.
Quent then waited anxiously, like an expectant father, for eggs to be produced in the field. “My main concern was whether the butterflies had mated because they can sometimes panic when they are released and immediately disperse, and if they disperse too far there is a big risk that the males and females never find each other to mate,” he said. “We unfortunately had one of the coldest and wettest springs in years, which would have seriously curtailed butterfly activity.” Quent was encouraged when he found eggs at the Waikato site in early November, but his hopes were dashed when they proved to be infertile. However, more eggs were discovered there in early December and, to Quent’s immense relief, they produced caterpillars.
Visits to the field sites in the Waikato in mid-December revealed a number of adults still flying around, which was encouraging because it meant they were capable of surviving for 2–3 weeks (the equivalent of an old-age pensioner in white admiral butterfly terms!). As an additional insurance measure, some eggs were collected from the site and taken back to Tamaki where they could be reared on in safety. The butterflies that emerged were returned to the Waikato field site in January, where second generation butterflies were readily observed, indicating they had also made it through successfully on their own.
“The females can lay up to 200 eggs each and the caterpillars have a good appetite for Japanese honeysuckle,” said Quent. “As far as predation is concerned, we suspect white admiral larvae will fall victim to wasps, but white admiral larvae are better camouflaged than monarch larvae and they develop much faster, so are exposed to predation for less time. The small larvae also have a ‘trick’ to avoid predators – they construct a ‘pier’ on the tip of a leaf, made out of silk and frass, which serves as a refuge from predators that search the leaf, but do not notice the pier beyond.
“Now we have to wait and see how it goes from here, but things are looking really promising – quite an achievement considering all the hurdles we had to jump to get this far,” said Quent modestly. Next spring we hope to be able to begin harvesting butterflies from the two initial sites to supply other areas that need them. “This project has thrown a number of ‘curve balls’ at us, yet with perseverance, our experienced team has achieved the almost impossible,” remarked Team Leader Lynley Hayes.
This project is funded by the National Biocontrol Collective.