Category: Invertebrates

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Huddling for Warmth

Beaver in snow, Courtesy US FWS
Beaver in snow
Image Courtesy US FWS

When temperatures dip below freezing and wind hurries on its way, we often find ourselves looking for another warm body to huddle near and share heat. Children snuggle into laps and dogs lean close.

Many animals huddle to stave off the cold. Species that are strong individualists in balmy seasons seek warmth from a group when temperatures drop. Many non-colonial rodents will share a den come winter.

[Kevin Colver recording: Songbirds of the Southwest Canyon Country]

Pygmy nuthatches jam themselves tightly together into tree cavities as do flying squirrels. Through the winter, worker honeybees huddle tightly around a central patch of wax comb where developing larvae are growing. The larvae die if temperatures drop below 83 degrees, so a living blanket of worker bees shivers to generate the heat equivalent to a 40 watt incandescent bulb.

An animal loses heat in direct proportion to its surface area. By huddling together, each animal reduces its exposed surface area. This in turn allows them to reduce their metabolic rate and so conserve energy at a time when food can be scarce or inaccessible.

Nests or dens occupied by numerous individuals can be much warmer than ambient. A snow covered lodge with at least 2 beaver occupants can be as much as 35 degrees warmer than the outside air temperature. A study of taiga voles showed that underground nests containing 5 to 10 residents remained 7 to 12 degrees warmer than the surrounding soil and up to 25 degrees warmer than the air above. Individuals take turns going out to forage so their nest remains toasty.

Living in close proximity does have its problems. Disease and parasites are readily transmitted in tight quarters. Local food competition could potentially lead to hunger or starvation. Predators may more easily discover prey in groups. But for many animals, the advantages of huddling for warmth far outweigh the risks during our chilly winter months.

This is Linda Kervin for Bridgerland Audubon Society.
Credits:

Photos: Courtesy US FWS

Audio: Courtesy Kevin Colver, https://wildstore.wildsanctuary.com/collections/special-collections, https://wildstore.wildsanctuary.com/collections/special-collections

Text: Linda Kervin, Bridgerland Audubon Society
Additional Reading:

Life in the Cold: An Introduction to Winter Ecology. Peter Marchand. 1991, University Press of New England. https://www.amazon.com/Life-Cold-Introduction-Winter-Ecology/dp/0874517850

Lives of North American Birds. Kenn Kaufman. 1996, Houghton Mifflin Company. https://www.amazon.com/American-Peterson-Natural-History-Companions/dp/0395770173

The Birder’s Handbook. Paul R. Ehrlich, David S. Dobkin and Darryl Wheye. 1988, Simon & Schuster, Inc. https://www.amazon.com/Birders-Handbook-American-including-Regularly/dp/1435277589

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Gall Insects

Rabbit Brush Galls
made by a tephritid fly Aciurina trixa
Image courtesy and Copyright Jim Cane
Fly identification courtesy Gary Dodson

Does Utah have more Gauls than Caesar conquered? Certainly not Gaulish peoples of the ancient Roman Empire, but yes, galls of the vegetal kind we have aplenty. Galls are small protuberant growths on plants that are induced hormonally by insects, nematodes, and microbes. For its resident juvenile insect, the gall is a sort of edible fortress.

Some plant galls made by insects persist into winter, when they are more apparent to the naturalist’s eye. Looking at just rabbitbrush, you can find a menagerie of galls shaped like peas, pineapples and spindles that were formed from leaves, buds and stems. No growing tissue is immune to galling. The morphology of a gall is often diagnostic for the species of juvenile insect within. Gall-making insects are all tiny and include gall midges and tephritid flies, cynipid gall wasps, various nondescript moths, and any number of aphids and their kin.

One aphid causes the unsightly brown galls on branch tips of blue spruce, a bane to homeowners. Another aphid forms the pea-shaped galls that swell leaf petioles of aspens and cottonwoods. On sagebrush can be found a leaf gall whose soft surface surpasses that of a puppy’s ear. Oaks and willows host a remarkable diversity of galls. One oak gall was formerly used for tanning leather and making inks because it is rich in tannic acids. The Hessian fly is of grave agricultural importance today because its stem galls weaken wheat stems, causing them to lodge over.

Tephritid fly Aciurina bigeloviae
galls on Rabbitbrush
Image courtesy and Copyright Jim Cane
Fly identification courtesy Gary Dodson

But these are exceptions; most galls are of little or no ecological or economic importance. For that reason, most galling insects remain understudied by all but a handful of passionate specialists. Finding plant galls is easy, and once you begin to notice them, you will find it hard to stop. There is no guide to Utah’s plant galls, but we list several starting references for you on our web site.

This is Linda Kervin for Bridgerland Audubon Society.

Credits:

Theme: Courtesy & Copyright Don Anderson as performed by Leaping Lulu
Photos: Courtesy and Copyright Jim Cane
Text: Jim Cane, Bridgerland Audubon Society
Voice: Linda Kervin, Bridgerland Audubon Society

Additional Reading:

Sagebrush Gall made by the fly Rhopalomyia pomum, https://bugguide.net/node/view/200946
Robert P. Wawrzynski, Jeffrey D. Hahn, and Mark E. Ascerno, Insect and Mite Galls, WW-01009 2005,
University of Minnesota Extension, https://www.extension.umn.edu/distribution/horticulture/dg1009.html

Willow Cone Gall Midge
Image Courtesy and Copyright Jim Cane

Field Guide to Plant Galls of California and Other Western States by Ron Russo
ISBN: 978-0-520-24886-1 https://www.amazon.com/California-Western-States-Natural-History/dp/0520248864
Gall, Wikipedia, Wikimedia Foundation, Inc., https://en.wikipedia.org/wiki/Gall (Accessed Dec 2010)
Gagné R (1989) The plant-feeding gall midges of North America. Cornell University Press, Ithaca
https://www.amazon.com/Plant-Feeding-Midges-North-America-Comstock/dp/0801419182

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The Brine Shrimp of Great Salt Lake

Brine shrimp life cycle, Courtesy University of Utah<br/>Genetic Science Learning Center https://learn.genetics.utah.edu/content/gsl/foodweb/brine_shrimp/index.html
Brine shrimp lifecycle
Courtesy University of Utah
Genetic Science Learning Center

Hi, this is Mark Larese-Casanova from the Utah Master Naturalist Program at Utah State University Extension.

I can still remember the colorful advertisements for Sea Monkeys in the back of comics books that I read as a child. For just $1.75, I could have a “bowl full of happiness!” It wasn’t until I visited Great Salt Lake thirty years later that I realized what sea monkeys really were. They certainly weren’t tiny, web-footed humans, and they definitely didn’t have little crown-like antennae. But, it was exciting to think that we have an enormous Sea Monkey aquarium right here in Utah.

Sea Monkeys are actually brine shrimp of the genus Artemia, and Great Salt Lake is full of the species Artemia franciscana. These tiny crustaceans, along with the brine fly’s aquatic larvae, are the foundation of the Great Salt Lake Ecosystem. Millions of birds visit Great Salt Lake each year to feed on brine shrimp during migration or while nesting.

Brine shrimp nauplii from the Great Salt Lake, Courtesy USGS see https://ut.water.usgs.gov/shrimp/
Brine shrimp nauplii
from the Great Salt Lake
Courtesy USGS

Not much can live in Great Salt Lake, with its salt concentrations as high as 25%. But by adapting to these conditions, brine shrimp avoid many predators and have little competition for the abundant algae and bacteria that grow there.

Beginning in late winter or early spring, as the water temperature increases and there is an influx of fresh water to the lake, brine shrimp hatch from cysts, which are hard-shelled dormant eggs. The brine shrimp larva, also called a nauplius, survives on a yolk sack for the first 12 hours, but then feeds on algae as it grows into an adult.

Some species of Artemia have only females, but the Great Salt Lake population has both males and females. The male can be distinguished by his ‘grasper’ antennae, which almost look like a giant handlebar moustache, and the female can often be seen with two small, orange or pink egg sacs at the base of her tail. When conditions in the lake are good, such as with high oxygen and relatively low salt concentrations, female brine shrimp will give birth to live nauplii. But, if salt concentrations increase due to drought in summer, or when water temperature drops in late fall, females switch to making more cysts to ensure the survival of future generations. As winter passes, and spring starts to make an appearance, the life cycle of the brine shrimp starts all over again.

To learn more about brine shrimp, be sure the visit the Great Salt Lake Institute’s web site at greatsaltlakeinstitute.org. I encourage you to visit Antelope Island State Park where you can catch brine shrimp from the marina on the north end of the island. All you need is a bucket… and a little sense of adventure.

Credits:

Photos: Courtesy USGS https://ut.water.usgs.gov/shrimp/
Brine Shrimp Lifecycle, Courtesy University of Utah Genetic Science Learning Center
Theme: Courtesy & Copyright Don Anderson Leaping Lulu
Text & Voice: Mark Larese-Casanova

Additional Reading:

USGS, Utah Water Science Center, Brine Shrimp and Ecology of Great Salt Lake. (Courtesy Internet Archive Wayback Machine, Apr 15, 2008) https://wildaboututah.org/wp-content/uploads/080415-Wayback-USGS-Brine-Shrimp-and-Ecology-of-Great-Salt-Lake.pdf Formerly: https://ut.water.usgs.gov/greatsaltlake/shrimp/

Brine Shrimp, Genetic Science Learning Center, University of Utah, https://learn.genetics.utah.edu/content/gsl/foodweb/brine_shrimp/

Salt Lake Brine Shrimp, https://saltlakebrineshrimp.com/harvest/

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Ladybird Beetle Migration

Ladybird Beetle
Courtesy US NPS.gov
Sally King Photographer

Migration brings to mind the exhaustive flights of migratory birds or the treks of large herds of hoofed mammals. But some insects migrate too. You may be aware of the story of migrating monarch butterflies and their mountain home in Mexico. But did you know that some of our familiar ladybird beetles of nursery rhyme fame also migrate? They really do “fly away home”?

Both in the larval stage and as adults, many species of ladybird beetles feed voraciously on aphids. Their fondness for aphids and scale insects has made them a very popular biological control agent. In 1887, a group of Australian species was imported into California to deal with an Australian scale insect that was devastating the citrus crop. These ladybird beetles were the first exotic insects to be introduced into North America for use as biological control agents. Within a year, the citrus crop was saved.

Ladybird beetle larvae hatch in the spring and devour aphids for about a month. They then pupate and soon emerge as adults. If there are insufficient aphids to feed these adults, they fly away, migrating to overwintering sites in the mountains. There they eat pollen to build up fat reserves. Ladybird beetles use the wind to loft their migration; waiting for a strong breeze in the correct direction before departing. As winter approaches in their mountain retreats, they congregate in the thousands, aided by the release of an olfactory attractant. If you are lucky in your mountain travels, you may come across one of these amazing masses of bright red beetles.

Come spring, they will mate, take wing and descend to their lowland aphid feasts, thus completing the cycle.

Our theme music was composed by Don Anderson and is performed by Leaping Lulu.

This is Linda Kervin for Bridgerland Audubon Society.
Credits:

Photos: Courtesy US NPS Sally King Photographer,
https://www.nps.gov/band/naturescience/moreinsects.htm
Text: Linda Kervin & Jim Cane, Bridgerland Audubon Society
Theme Music: Don Anderson & performed by Leaping Lulu,
https://www.amazon.com/Trout-Berry-Wasatch-Stomp-Corinth/dp/B0014ORPCM

Additional Reading:

Peter J. Marchand, Autumn: A Season of Change (Hanover, NH: University Press of New England, 2000)

https://www.amazon.com/Autumn-Season-Peter-J-Marchand/dp/0874518709

Arthur V. Evans & Charles L. Bellamy, An Inordinate Fondness for Beetles (Berkeley, CA: University of California Press, 1996)

https://www.amazon.com/Inordinate-Fondness-Beetles-Arthur-Evans/dp/0520223233