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Cofrin Center for Biodiversity

Archive for the ‘Econotes’ Category

American Bittern

Keen-eyed botanist Gary Fewless spotted this American Bittern (Botaurus lentiginosus) in the Cofrin Arboretum. American Bitterns used to be fairly common in the large marshes on the west side of the Bay of Green Bay, nesting in cattails and in sedge meadows in Atkinson, Sensiba, and Peters marsh. In recent years, as Phragmites australis has invaded and replaced cattails in much of the marshes in northeast Wisconsin, we have seen a decline in the numbers of nesting pairs of American Bitterns.

The loss of large wetland areas to development and degradation by invasive plants like Phragmites and pollutants has taken a toll on bittern populations in the United States. Overall American Bitterns are half as common as they were 40 years ago.

American Bittern

American Bittern at UW Green Bay

This individual is the first to be sighted on the UWGB campus and is probably a young bird that is looking for suitable habitat as it prepares to migrate. According to Richter Museum Curator Tom Erdman, these individuals often return to a location they sampled the previous fall. So perhaps this one might return to nest in the spring.



Metamorphosis is Tough!

And you thought growing up was tough…try metamorphosis. This unfortunate insect is probably a Spongillafly. It should have long lacy wings (see link for comparison), however, something must have happened as it emerged from its pupae.

When botanist Gary Fewless found this tiny creature, he had no idea just how unique it was.  He found a spongillafly, an insect that is seldom collected as adults. And he found a living individual whose abdomen and wings were highly deformed. 

At least we think it is a spongillafly. We are not completely sure of course, since we are making an identification from a photograph of a badly deformed specimen, but that is entomologist Mike Draney’s best guess, based on the size of the eyes and the pigmentation of the wings. And what exactly is a spongillafly? They are insects in the Order Nueroptera, which also include the more familiar lacewings and ant lions (aka doodlebugs if you’re from the South).  Most Neuropterans are predators. However, spongillaflies are unique, because they are parasites that spend their larval stage underwater feeding on freshwater sponges.  Only 6 species are found in the spongillafly family (Sisyridae) and only 3 of these, Climacia aerolaris, and Sisyra fuscata, and Sisyra vicaria are found in the Great Lakes region.

The adults look similar to brown lacewings. They spend their time flying, feeding and scavenging on other invertebrates, mating and laying eggs on vegetation overhanging streams and lakes usually at dusk or after dark, which is one reason they are so seldom collected.  When the larvae hatch, they fall into the water and float around until the find a sponge. (Wait a minute…there are sponges in Wisconsin?  Well—yes, but we’ll tackle that topic in a later blog. ) The spongillafly larvae use their piercing mouth parts to suck body fluids from the sponge tissues. They don’t kill the sponge and will stay with the same sponge until they are ready to pupate. It is likely our specimen spent its underwater time feeding on its sponge and generally enjoying life.  When it was ready to metamorphose it climbed out of the water, found a site it liked under a rock or tree bark and then spun a silken cocoon around itself for protection. It remained in the cocoon all winter as a hibernating larva, waiting until the warm spring weather to even begin to pupate.  And that is where something went terribly wrong. 

What goes on in the pupa? From our perspective, pupation might seem like a pleasant rest in a bed of silk, this is hardly the case.  Beneath its silken wrap, dropping levels of juvenile hormones trigger a cascade of changes in the developing insect. First, chemical signals are released that signal the epidermal cells to release enzymes that digest the larvae’s cuticle (skin). The cuticle is broken down into and reused to make new parts. Basically the larva is killing its own skin cells.

At the same time special clusters of cells in the body called imaginal discs become active and elongate, using the digested epidermis to  build wings, eyes, antenna, and reproductive parts, as well as the new exoskeleton of the adult insect.  These discs are aligned in pairs and their development is genetically controlled. Any mutation in these genes can result in malformations in the adult, so that a leg might grow where a wing should be.  In fact, it was the study of mutations like these in fruit flies that greatly increased our understanding of how the process and genetic control of early developments occurs.   If anything goes wrong during this period of genetic communication and rapid development the adult will not form properly.

Our insect has all its parts in the right places, so a genetic mutation is unlikely. It is more likely that the pupa was damaged from the outside as it was developing. If the pupa is crushed or bent during this period of radical re-arrangement, the underlying developing adult structures can also be damaged. The developing pupa does not have much capability to repair structures after they have formed.

Damage can also occur after the adult emerges, but before its exoskeleton dries and hardens. The newly emerged insect is soft and its wings are shortened and curled. It must pump fluid from its abdomen into the veins of the wings to enlarge and elongate them.  (See this photo of a newly emerged brown lacewing.  It has nearly finished uncurling its wings.) If the insect falls or is crushed while it is still soft, wings or legs can harden in bent positions. If the abdomen is damaged, internal injuries can result, and the insect will usually die.

Parasites can also cause improper development. Gregarine parasites are protozoa that live in the guts of many different insects including Nueroptera.  The insects are infected by spores that fall onto the eggs as they are being laid.  The spores are eaten by the insect larva and reproduce asexually inside the gut, absorbing nutrients through micropores in their wormlike bodies. During pupation the parasites switch to sexual reproduction, forming spores that are released through the pupal case and dust the body surface adults as they crawl out of the cocoon. They pass the spores onto their offspring when the spores fall onto the eggs as they are laid.  Heavy gregarine infections are known to result in wing deformations in developing butterflies because the butterflies are too weak to hold themselves up or to inflate their wings.

We are not quite sure what went wrong with this individual.   Regardless of what happened to this insect it is unlikely it survived very long after the photo was taken.

A Returning Rabble of Admirals

Red Admiral, Photo by Ron Eichhorn

Red Admirals are one of the first butterflies seen in spring. Photo by Ron Eichhorn

This past weekend I stepped into my garden to be greeted by several red admiral (Vanessa atalanta) butterflies. According to our phenology records, the first sightings were in early April, but this year we started receiving reports of larger groups (rabbles) of admirals in late April. This is unusual for this species, which is territorial and usually found singly. It may be that warm southern winds helped to push the butterflies north.

Red admirals can only survive mild winter temperatures, so it is most likely that the butterflies we see in April are migrating from farther south. According to WI butterflies there are occasional outbreaks of large numbers of red late June and early July. The last event was in 2007. It is not known what causes these outbreaks, but we do know they are the offspring of those early migrants who laid their eggs on nettles in early May. A friend who found herself in an outbreak a few years ago at Point au Sable said there were so many that she could hear them flyinng. Perhaps this year we might be privileged to see hundreds of these beautiful butterflies this summer. They are common through northeastern Wisconsin; look for them in woodland openings and suburban areas. And let us know at our phenology pages.

You can follow the migration on University of Iowa’s <em>Vanessa Migration website. Entomologist Royce J. Bitzer has been tracking the migration of these and other butterflies since 2001. You can enter your data and follow the North American migration in google maps.

Pollen Eater

Soft-winged flower beetle feeds on pollen of Marsh Marigold.

Soft-winged flower beetle feeds on pollen of Marsh Marigold.

Marsh marigold (Caltha palustris) is a beautiful spring ephemeral flower locally common in wet forested areas.  Baird Creek in Green Bay offers spectacular views of this flower. This photo of a soft-winged flower beetle called Collops feeding on protein-rich pollen (and perhaps sugary nectar) shows that it’s not only humans that are attracted to this early bloomer. 

Pollen is an important food source for many herbivorous organisms that mainly feed on nectar or fruits that are often low in protein. In some Coleoptera pollen provides the nutrients needed to for growth and also to produce eggs.

Soft-winged flower beetles (family Melyridae) are not a particularly well-known group of beetles, despite the fact that over 500 species occur in North America.  Many feed on pollen, and although it would seem that this would be deleterious to the plant, the beetles inadvertently transfer pollen between flowers and can be effective pollinators, just like their more famous (and graceful) relatives, such as butterflies. 

Both flower and beetle are not only colorful accents in our spring landscape, but they also have roles to play in their ecosystems, and help to support other organisms and increase the biodiversity in our region.

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