Effects of extreme weather events on butterfly populations

Increasingly frequent extreme weather events could threaten butterfly populations in the UK and could be the cause of recently reported butterfly population crashes, according to research from the University of East Anglia (UEA).

Researchers investigated the impact of Extreme Climatic Events (ECEs) on butterfly populations. The study shows that the impact can be significantly positive and negative, but questions remain as to whether the benefits outweigh the negative effects.

While it is well known that changes to the mean climate can affect ecosystems, little is known about the impact of short-term extreme climatic events (ECEs) such as heatwaves, heavy rainfall or droughts.

Read the university press release.

PDF version:  extreme-weather-effects-may-explain-recent-butterfly-decline-press-release-uea

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Tricking moths into revealing the computational underpinnings of sensory integration

 

Our nervous systems are remarkable translators, channeling information from many sources and initiating appropriate behavioral responses.

But though we know how a lot about how neurons work, scientists do not fully understand how the nervous system integrates stimuli from different senses. You may smell smoke and feel heat, but how does the brain combining and interpret these different stimuli, signaling you to phone the fire department?

It turns out that insects are attractive models to investigate questions about integrating information from different sensory pathways. The hawkmothManduca sexta, uses a long, trunk-like proboscis to drink up sweet nectar meals from obliging flowers. A research team led by University of Washington biology professor Tom Daniel has teased out how hawkmoths integrate signals from two sensory systems: vision and touch.

Their findings, published Oct. 24 in the Proceedings of the National Academy of Sciences, illustrate the computational basis of this integration, which may serve as a general model for insects, other animals and humans.

“Sensory integration remains one of the more interesting tasks that even simple nervous systems accomplish,” said Daniel. “From tasks like reaching in humans to nectar-feeding in insects, our challenge has been developing experimental ways to reveal the mechanisms and circuitry that underlie combined visual and mechanical sensing.”

The hawkmoth’s proboscis is longer than its body, so it can probe deep within a flower to find nectar while the hawkmoth hovers above. Even as the flower sways and blows with the wind, hawkmoths have been observed adjusting their position to track with the flower’s position.

Scientists can study tracking behavior in the laboratory using specially designed, artificial flowers constructed with their own small nectar pods. Hawkmoths respond to these pre-packaged dinners similarly to real flowers, and — if researchers manipulate the artificial flower to move when a hawkmoth is feeding — the hawkmoth adjusts its position to keep up.

In addition to its drinking duties, the proboscis is also a sensory organ, relaying information about the moving flower it is touching. To see how input from different sensory systems contributed to tracking behavior, Daniel’s team modified the artificial flowers to simultaneously deliver contradictory visual and tactile cues: the flower’s petals, which the hawkmoth follows using its eyes, move independently from the nectar pod, which the hawkmoth proboscis touches. By studying how moths respond to discordant visual and touch signals, they hoped to decipher how the hawkmoth brain processes and combines inputs from both sensory systems.

“Typically, to study how a particular sense contributes to a behavior, scientists try to design experiments in which the animal only receives that one kind of sensory cue,” said UW postdoctoral researcher Eatai Roth, who is lead author on the paper. “But this doesn’t reflect what’s happening when an ensemble of senses contribute concurrently. Our approach — sensory conflict­ — bombards the animal with rich multisensory cues simultaneously. This allows us to model how information is processed and combined concurrently across different senses.”

Daniel and his team tested how well hawkmoths tracked while feeding on the discordant flower. When the nectar chamber moved but the rest of the flower was still, the moths were generally able to sway in response to their moving meal. But when they kept the nectar chamber still and moved the flower petals, moths only swayed slightly. This indicated that, for feeding, tactile information transmitted by the proboscis may be a more important sensory input than vision.

“In nature, the visual and touch cues largely agree and either sense alone is enough for the job. Having both provides redundancy, a backup just in case,” said Roth. “But when we present the moth with conflicting stimuli, it must decide how to balance the mismatched information — which cue to follow. And it turns out, quite surprisingly, that touch beats out vision in this sensory tug-of-war.”

They measured hawkmoth positions during the tests and used these data to describe hawkmoth behavior in terms of a mathematical model. Though the sense of touch appeared to play a greater role in tracking behavior, moths do not rely on this sense alone. Their mathematical model indicated that the moth brain uses a simple additive or “linear summation” model to integrate signals from the proboscis and the eyes. And though moths rely heavily on the touch cues from the proboscis, the model suggests that both the visual and touch senses are acute enough for the moth to follow the flower.

The team used this model to predict how moths would behave in a new discordant setting in which the nectar chamber and flower were both moving, but quite differently. The researchers tested these predictions on a different set of hawkmoths, and they responded to this floral discord just as the model predicted. Daniel and his team believe that the mathematical underpinnings they describe here may represent a common mode of signal integration in animals.

Senior author is Simon Sponberg, a former UW postdoc who is currently an assistant professor in the Department of Physics at the Georgia Institute of Technology. Co-author is UW graduate, Robert Hall. The research was funded by the Air Force Office of Scientific Research, the Washington Research Foundation and the University of Washington.

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For more information, contact Daniel at danielt@u.washington.edu or 206-543-1659 and Roth at eatai@uw.edu or 205-543-7335.

Grant numbers: FA8651-13-1-0004, FA9550-14-1-0398.

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Final Forecast of the 2016 Season — Week Beginning 2016 Sept 24

American Snout on thoroughwort in Howard Co MD [2016 Sept 20, photo by Jim Wilkinson]

A fresh American Snout on thoroughwort in Howard Co MD [2016 Sept 20, photo by Jim Wilkinson]

It’s the month of final hurrahs for summer butterflies; except for a few irruptive southern migrants like Common Buckeye we’re seeing the last of the large flights of butterflies for the season. If you’re lucky enough to have found the few spots of sunshine in the area today, or get out after the cold front passes tomorrow, you’ll still have some good butterfly observing and a chance at a couple of FOYs still this month.

Still MIA is Clouded Skipper, which is being seen in some numbers as far north as the Raleigh area but for which I have not yet seen any local records this year. Ocola Skippers are still being seen throughout the region, and Long-tailed Skippers are showing up in many locations. The normal grass skippers have peaked, including Sachem, but a new influx or emergence of Fiery Skippers is currently dominating a lot of area lantana patches. A few Leonard’s Skippers are still on the wing in their preferred habitat.

Monarchs are showing a strong flight in parts of the area, including dozens this week on the National Mall. A growing hypothesis is that the “dearth” of Monarchs in the mid-Atlantic area in the fall where they used to be common owes more to changing biogeography (and especially nectar sources) than it does to sheer numbers.

With one exception, swallowtail numbers are declining. There’s currently a fresh brood of Pipevine Swallowtails on the wing, where again a dozen or more were frequenting the Haupt Garden near the Smithsonian Castle in downtown DC this week. Palamedes is probably on the wing (and will be for another couple of weeks) in extreme Delmarva, and at least one Giant Swallowtail was noted in the past couple of weeks in the region.

Sleepy Oranges are in flight now; in some places in rather large numbers. Cloudless Sulphurs also are about in good numbers.

Hairstreak numbers also are dropping; exceptions are White M (several observations this week) and Gray. Azures still showed up very occasionally, and even Eastern Tailed-blues are tattered and dwindling. Great Purple Hairstreak should still be flying, however, in southern MD and DE. A few American Copper sightings came in, but no recent Bronze Copper observations (this species flies well into October on the Delmarva Peninsula).

Good numbers of Viceroys and Red-spotted Purples were also well represented in reports this week, as were laggard Meadow Fritillaries and diminishing numbers of Variegated Frits. Fresh Red Admirals were on the wing, giving hope for a final good flights. Commas and Question Marks were also reported; these are mostly on windfall fruit or puddling.  Fresh Snouts are out too.

This will be the last Mid-Atlantic Butterfly Field Forecast for the 2016 season, which wraps up each year on the last weekend of September. But if you want to continue hearing about sightings until the first heavy frosts, follow MDLepsOdes on Google Groups.   Thanks for following us this year, and look for the Forecast to return in April 2017.

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Mid-Atlantic Butterfly Field Forecast for the Week Beginning 2016 Sept 17

One of several Sleepy Oranges on the trails of the Pickering Creek Audubon Center last Sunday [2016 Sept 11, MD Talbot Co, photo by REB]

One of several Sleepy Oranges on the trails of the Pickering Creek Audubon Center last Sunday [2016 Sept 11, MD Talbot Co, photo by REB]

This weekend promises – or at least hints at – rain, which the area needs very badly as the nectar sources typically don’t produce much nectar under drought stress. But the warm, dry weather has brought a spate of fall sightings locally and regionally.

Topping the list locally was Checkered White in Howard Co MD; there’s a large flight of Small (Cabbage) Whites currently in progress and I suspect there are more Checkereds among them for wont of close inspection. Little Yellow racked up a couple more (but sporadic) reports this past week, but it’s Sleepy Orange that has really piled on the sightings – a veritable irruption in northern VA and some dozens in Talbot Co on the MD Eastern Shore. Cloudless Sulphurs are also have a very strong flight, abetted in recent days I suspect by the southeasterly winds.

For many of us, FOY Painted Ladies showed up in the past few weeks, including four near Centreville MD in the ROW between Route 301 and Carville Price Road, which parallels 301. This is an especially rich, moist, nectar laden oasis that anyone on the way to the Delaware beaches or up to Eastern Neck NWR should check out en route. Filled with swallowtails (Spicebush, mostly, but also a few Eastern Tigers, a single Black, and a probable Pipevine), Monarchs (among the most common butterflies there), Common Buckeyes, and a selection of skippers – multitudes of Silver-spotteds and lower numbers of Leasts and Sachem, some unidentified duskwyings, and a solitary Ocola.

Observers should keep their eyes on those Silver-spotted Skippers this time of year, as Long-tailed Skippers have been reported to our south and as far north as New Jersey and CT. So they are clearly on the move now. Common Checkered-skippers are also flying; they’re one of the highlights of fall when they’ve been scarce most of the rest of the year. Aaron’s, Broad-winged, and Salt Marsh Skippers are still flying as well. Still waiting to make an appearance locally are Clouded and Eufala Skippers.

Viceroys and Red-spotted Purples are out and about as well, as are pristine Commas and Question Marks. The former will be in their last brood but may persist through the first frosts; the latter will join us again as overwintering adults next March. Pearl Crescents are having their best flight of the season, and there were also a couple of reports of Silvery Checkerspots mixed in regionally.

A very few Summer Azure reports trickled in (one from my back yard in College Park just this morning). There’s a modest flight of Eastern Tailed-blues (seems not to have been a particularly good year for them), and a number of White M reports to complement the much more widely observed Gray Hairstreaks. A couple of Red-banded Hairstreaks also make the list this week. No reports of coppers of any kind, or of Great Purple Hairstreak.

This cool weekend will again give way to high temps, high humidity and hot sunshine by midweek. If you dodge the clouds and and showers this weekend, please report back what you find to us for the next Forecast by commenting here at https://leplog.wordpress.com/ or by posting to Google Groups at MDLepsOdes.

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Mid-Atlantic Butterfly Field Forecast for the Week Beginning 2016 Sept 10

Tom Stock's photo this week of Leonard's Skipper on blazing star (Liatris) at Soldiers Delight in Baltimore Co MD.

Tom Stock’s photo this week of Leonard’s Skipper on blazing star (Liatris) at Soldiers Delight in Baltimore Co MD.

Diversity and numbers are up this week, a last hurrah for the season, led by the seasonal emergence this week of Leonard’s Skippers at Soldiers Delight in Baltimore Co.  It’s all downhill from here, folks!

The major explosion of Sachems over the last three weeks is already starting to show wear and tear, but the numbers are still high, while Peck’s Skipper numbers still seem to be building. Singletons or low numbers of Crossline and Little Glassywing came in; no reports of either Broken-dash, Swarthy or Dun. Fresh Silver-spotted Skippers are flying, and large-bodied skippers like this should be double-checked to make sure they aren’t Long-tailed (which often as not lacks the long tail and then looks a lot like Silver-spotted at first glance). Fiery Skipper hasn’t been seen much after a spate of early promising sightings.

Ocola Skippers were widespread – and in fact widely reported well into New England (NY, CT, MA).

Otherwise there hasn’t been much change since last week, except to note the burst of Cloudless Sulphurs (they were omnipresent at Eastern Neck NWR last weekend). Fresh swallowtails – Spicebush, Black, and (surprising to me) Zebra – were also zipping around the butterfly garden there. Immaculately fresh Pipevine Swallowtails were noted several times on DC’s National Mall this week.

Clouds of Monarchs were also at Eastern Neck, predominantly female and clearly already in reproductive diapause with no interest expressed by any of the males. Intent nectaring for the flight south.

Tomorrow looks like a scorcher to (we hope) end the torrid summer, but Sunday looks picture perfect for butterflying from the forecast. If you go out, please report back what you find to us for the next Forecast by commenting here at https://leplog.wordpress.com/ or posting to Google Groups at MDLepsOdes.

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Mid-Atlantic Butterfly Field Forecast for the Week Beginning 2016 Sept 3

Salt Marsh Skippers are flying in coastal habitats; look for them on goldenrod and salt marsh fleabane [photo courtesy Barry Marts, 2016 Aug 20]

Salt Marsh Skippers are flying in coastal habitats; look for them on goldenrod and salt marsh fleabane [photo courtesy Barry Marts, 2016 Aug 20]

With the remnants of Hermine due to visit the mid-Atlantic toward the middle and end of the Labor Day weekend, the Forecast is a little up in the air (pun intended) for what’s likely to be out and about in the markedly cooler weather. And of course, there’s always the possibility that some southern migrants might be pushed northward up the coast, although this storm is unlikely to produce much in the way of butterfly fallout.  If we get rain from it, that might freshen up the nectar sources a bit.

It’s been a good week locally for grass skippers, after a rather anemic summer so far for these species. Zabulon Skippers are hanging on in some spots longer than is their normal wont, and Common Checkered-skippers are making a good showing throughout the region. Fresh female Sachems are out this week to join the clouds of male Sachems flying over the past ten days, and the new brood of Peck’s Skippers seems pretty much everywhere too (and by that I mean on most buddleia bushes with any amount of bloom on them). Other grass skippers are less common. Least Skippers were ubiquitous this week in the right habitats. Salt Marsh and Aaron’s Skippers are flying well along DE coastal marshes (Bronze Copper is still flying there as well); Salt Marsh Skipper this time of year is especially fond of salt marsh fleabane as a nectar source. Ocola Skipper is having a banner year so far with most observers reporting multiple sightings from field trips. No reports yet of Leonard’s Skipper, but I suspect it will be seen this weekend if the weather cooperates; neither Clouded nor Long-tailed Skippers have been reported locally yet either but could show up any day.

Among the duskywings, Horace’s is especially plentiful this late summer, although Wild Indigo is still in flight as well.

Cloudless Sulphurs are now pretty much overspread in the mid-Atlantic; look for them especially on various sages. Little Yellow is having its best year in the past four or five summers, although some usual locations are still missing them.

Fritillaries on the wing have included surprisingly long-lived Great Spangled, increasing numbers of Variegated (possible the prelude to a huge final fall flight), and a few Meadow Frits. Red-spotted Purples, Red Admirals, both anglewings (which will hibernate and re-emerge in the spring), Common Wood-nymph, both emperors, and Northern Pearly-eye round out the assortment of other widely reported nymphalids this week; no Viceroys made the lists, nor did any Ladies.  Common Buckeyes are living up to their name but none of the fall “rosa”form have been reported yet locally.

Eastern Tiger Swallowtails, Black Swallowtails, and fresh Pipevines are currently on the wing. Few reports of Spicebush, which seems to have finished up, and no Giant sightings.

If Hermine doesn’t wash out the weekend and you make it out into the field, please report back to us for the next Forecast by commenting here at https://leplog.wordpress.com/ or posting to Google Groups at MDLepsOdes.

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Mid-Atlantic Butterfly Field Forecast for the Week Beginning 2016 Aug 27

Second-generation Delaware Skipper from the Lancaster PA area this week [photo courtesy Tom Raub]

Second-generation Delaware Skipper, one of several seen the same day, from the Lancaster PA area this week [photo courtesy Tom Raub]

This week begins the Season of the Sachem. Every lantana, every zinnia, every Joe Pye weed flowerhead has its golden-brown skippers in attendance, 99 percent of which will turn out to be Sachems. This week the preponderance is overwhelmingly bright orange males; females will turn out over the next week or 10 days in numbers as well.

Other grass skippers are still around, too, if dwarfed in number by Sachems. Fiery Skipper has yet to be seen in any numbers, but Southern Broken-dash is still being seen regularly if only as singletons. Ocola Skippers are well represented by sightings this week, especially the farther south one goes. Crossline, Tawny-edged, Dun, and Swarthy Skippers were few and far between, as was Little Glassywing; Silver-spotted Skippers have already begun to decline from a sizable brood only a week or two ago. The common duskywing in flight at the moment is Wild Indigo, although Horace’s is still around so each duskywing should be inspected. Dion Skippers in some numbers were reported last week and should be watched for in estuarine marshes on pickerel weed where it is blooming. Salt Marsh and Aaron’s Skippers remain on the wing in the coastal marshes.

The most interesting skipper sighting this week is of a local population explosion of Delaware Skippers as a fresh brood in south-central PA. While we normally think of Delawares as single brooded in our area, it is reliably double- or even triple-brooded farther south, and there are records in regional databases of late August and early September specimens still in pretty fresh shape that suggest this species is double-brooded here at least in some years (an irregularity much like Hessel’s Hairstreak that sometimes skips its summer generation in poor years responding to environmental cues we don’t fully understand). This time of year they might be confused if mixed in with fresh, bright male Sachems.

Summer nymphalids are wrapping up; a single Meadow Fritillary made the lists this week, and greater fritillaries are done for until 2017. Searches for female Dianas in the VA and NC mountains turned up empty but did score worn males; veteran observers in the mountains have noted this has been a poor flight year for Great Spangled, Aphrodite, Atlantis and Diana Fritillaries. A couple of Silvery Checkerspot reports have come in, but generally they are scarce in the current generation, and the normal large flight of Pearl Crescents seems to be much reduced this season. Comma and Question Mark were reported across the area, as was a single Mourning Cloak. The latter three should be looked for on windfall apples and pears in old orchards this time of year, along with Red-spotted Purple, Viceroy (if the orchard is near willow), ladies, and Red Admirals. Feeding trays with rotting fruit are also quite productive in late summer and early fall. Buckeye numbers are low but should be laying eggs on gerardia and plantain for a good final brood in late September and October.  Wet woods are still yielding a final generation of Appalachian Brown, and open meadows have the final flight of Common Wood Nymph.

Monarchs were reported by many if not most butterfly observers in the field this past week, including a dozen or more on the National Mall today. Red-banded and Gray Hairstreaks were reported, along with dwindling numbers of Summer Azures. Great Purple Hairstreak was noted in a few locations on the Eastern Shore over the past few weeks, as has Bronze Copper (in DE). American Coppers have not had a good year in the mid-Atlantic and the current flight is no exception.

Among the swallowtail tribe, Black and Spicebush are still flying; the large brood of Eastern Tiger Swallowtails two weeks ago has diminished sharply. Pierid diversity is up, with the best year in the past four or five for Little Yellows. Cloudless Sulphurs were widespread (although in modest numbers) as were Sleepy Oranges.

Butterfly observers should watch carefully over the next two or three weeks for Leonard’s Skipper, as well as for migratory Clouded Skipper and Long-tailed Skipper. Less likely but also possible in the waning summer and early fall are Eufala Skipper and Whirlabout.

This weekend we return to high temps, high humidity and hot sunshine – generally good for butterflies but enervating for butterfly watchers. But should you make it out to winnow through the Sachems for other grass skippers, please report back what you find to us for the next Forecast by commenting here at https://leplog.wordpress.com/ or posting to Google Groups at MDLepsOdes.

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