insects – Biodiversity

Holiday Cluster Flies

Last week I was at a concert where two large fresh-cut trees had just been brought in. I noticed several insects lazily flying about the auditorium and when one landed nearby we recognized it as a cluster fly. I knew that cluster flies overwinter in attics and walls like Asian Ladybugs, but I wondered if they could also overwintering in Christmas trees. Last year I had seen these same insects shortly after we brought in a fresh-cut Christmas tree as well. Did they come in on the trees?

Cluster fly larvae are non-native imports from Europe. They are not considered invasive in northeastern Wisconsin because they are parasites on earthworms, which are also not native to our area. In the autumn adult flies search out protected over-wintering sites. In the wild these would be under bark or in dense vegetation or other crevices in rocky piles or cliff faces. Of course buildings mimic cliff faces to these insects, and the flies will cluster under siding and in walls or attics. Christmas tree farms are likely to provide good overwintering sites if there are brush piles or dead trees or sheds nearby. But it isn’t too likely they could use living Christmas trees successfully because there are few good places for them to hide.

I spoke with UW Madison entomologist Phil Pellitteri who agreed the flies are unlikely to find good winter protection in Christmas trees and suggested that the flies were probably in the building and were roused by warm outside temperatures. Wherever they came from they are slow and easy enough to catch. Unlike other “house” flies, cluster flies do not feed in our houses and are unlikely to spread disease.

Cluster Fly (Phormia rudis). Photo by Gary Fewless.

Are cluster flies a pest? That probably depends on how many there are in one place. They can sometimes accumulate inside walls and attics in large numbers. When temperatures rise on warm days some flies become active and make their way into living spaces. Once inside, they are not easily controlled by pesticides. Experts at the Entomology department at Penn State and UW Extension suggest killing flies trapped in walls or attics might makes matters worse because the dead flies will attract other more onerous pests like carpet beetles that would invade closets and rugs looking for wool and furs after they devour the flies.

Real Christmas trees are clearly the better choice for the environment when compared with artificial trees. They sequester carbon, produce less pollution and waste when recycled, and tree farms provide habitat that helps to preserve local biodiversity. Sometimes people are worried about that biodiversity, especially insects or spiders, coming inside with their trees. The best way to remove any stowaways is to give the tree a good shake before bringing it in the house. Fresh Christmas trees should never be sprayed with chemical pesticides, which are flammable and environmentally unfriendly. And of course sprays would ruin that wonderful fresh conifer scent.

References:

Phillip Pellitteri, University of Wisconsin Diagnostic Laboratory: http://www.entomology.wisc.edu/diaglab/

Insect Advice from Pennsylvania State Extension: http://ento.psu.edu/extension/factsheets/cluster-flies

University of Wisconsin Extension News: “Homeowners find fall insects unwelcome guests.” http://www.uwex.edu/news/read.cfm?id=153

The Nature Conservancy “Real versus fake Christmas trees” http://www.nature.org/photosmultimedia/real-vs-fake-christmas-trees.xml

How NOT to Control Gypsy Moths

Burlap tree wrap. — Burlap "skirt" tied around young oak.

One of the most common ways to try to control gypsy moth (Lymantria dispar) populations is to wrap tree trunks with control bands. These are simply burlap skirts that are wrapped around the tree. Gypsy moths feed on the leaves of the trees at night and then climb back down the tree trunk and hide under the bark or leaves during the day to avoid predators. The burlap skirts provide an ideal hiding spot for the caterpillars and they will congregate there in large numbers. This makes it easy to capture and kill them during the day. The burlap itself does not act as a trap, and actually increases the moth’s chance of surviving to adulthood, because it prevents predators like Blue Jays from seeing them. Burlap only works if the caterpillars are removed every few days. So if you are going to put up the burlap skirts, you must be committed to checking them every few days and killing the caterpillars by squishing them or by scraping them into a jar of soapy water so they drown.

We saw thousands of male gypsy moth flying around burlap skirted oak trees in one of the parks in Green Bay, Wisconsin in July of 2010. There were many females actually laying their eggs underneath the burlap. This is unfortunate because now there will be more work to remove egg masses this winter and spring.

Burlap lifted revealing gypsy moth pupae.

Some Links on How to properly use burlap tree skirts:

WI Gardener video clip http://www.uwex.edu/ces/gypsymoth/collectionband.cfm
tips on controlling gypsy moth throughout the year: http://www.uwex.edu/ces/gypsymoth/index.cfm?mo=6

Male (dark) and female (light) gypsy moths with egg masses.

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.

Pollen Eater

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.

Bullet ants

Today Dr. Draney caught a bullet ant (Paraponera clavata). To the locals it is called the 24 hour ant, because when bit the pain lasts for 24 hours. It is ranked as the most painful insect sting in the world and is second only to the giant Japaneese wasp (which is the size of your thumb) in terms of being the most dangerous insect in the world. Below you will see a picture of me and the bullet ant, which is nearly one inch long. Panama has been great and I would like to say hi to all my friends at Jackson School and Mrs. Van Rens.