Insects

All posts tagged Insects

Ian Stewart

These are the opening words of the poem ‘To a mouse’, written by the legendary haggis-eating Scottish poet Robert Burns in 1785 (which also contains the famous line oft-paraphrased as ‘The best-laid schemes of mice and men go often askew’). Although this is an apt description of mice it is also used to refer to all manner of small, obscure and reclusive animals and feather mites fit perfectly into this category.

Most people have never heard of feather mites which is hardly surprising. They are tiny brown arthropods which spend most of their lives flattened along the vanes of bird wing feathers where they were assumed to scavenge on feather debris and oily secretions and perhaps even rasp away at the feathers themselves. However, a remarkable study published last summer (Doña et al. 2018) examined the contents of mites’ stomachs using high-power microscopy and DNA analysis and found that their main food was fungi, and perhaps also bacteria and oil produced from the birds’ preen gland. Whether this means feather mites harm their hosts or are simply commensal remains to be seen.

Birds are assumed to acquire feather mites through physical contact with their parents while they are still in the nest, although they could also pick up mites from bumping into other birds at feeders or sharing the same dust bathing sites. Mites are quite easy to see if you are holding open a bird’s wing although with the naked eye they just look like a cluster of small dots (shown below).

We gained a whole new appreciation for these creatures when Shannon Modla of the University of Delaware kindly photographed some Gray Catbird feather mites under a light microscope. The magnified views show that they are long and thin with two pairs of legs at the front of their body and two pairs at the back (image below). The darker mites on the left and below are probably older mites with a hardened exoskeleton while the paler one on the right is probably a younger mite that has just molted.

Shannon was then able to view them under a powerful electron microscope and got some incredible images of their head as well as an egg (below).

To try to gain some insights into the biology of these enigmatic creatures we have been scoring the number of feather mites present on birds handled during the Delaware Nature Society’s Bird Banding project. Our simple questions were which bird species are most likely to have mites and whether the number of birds with mites varies according to the time of year.

Our first finding was that feather mites are quite common. We examined 448 birds belonging to 48 species and found that almost half of them (203 birds from 37 species) had mites on at least one of their wing feathers. We also found the proportion of birds with mites varies a lot between species. Over 75% of the Slate-colored Juncos, House Finches and Downy Woodpeckers that we examined had feather mites yet fewer than 15% of Ruby-crowned Kinglets, Common Yellowthroats or House Wrens had them. We also found that the proportion of birds with mites stayed quite consistent across the year with a noticeable peak in May.

This year we will be gathering more data on mites from the birds we band and then try to figure out why some birds are more likely to have mites than others, and why some have lots of mites while others have very few. Is it related to their body size perhaps, or how social they are, or maybe whether their beak is small and pointed enough to preen away the mites? So watch this space for updates on this new and fascinating DNS research project!

DNS has plenty of birding opportunities coming up soon, so sign up and enjoy the outdoors!

The Great Backyard Bird Count ~ Coverdale Farm Preserve

The Great Backyard Bird Coount: Kent County Tour ~ Abbott’s Mill Nature Center

Owls and Other Winter Raptors ~ Ashland Nature Center

 

By Lori Athey, Habitat Outreach Coordinator

It is high summer now and my early summer flowers are looking a bit tired while the late summer/fall show has yet to begin. Nonetheless, there is a lot of wildlife activity in my garden right now. The pollinators are all over the Echinacea/Purple Coneflower, Coreopsis, Butterflyweed and Beebalm, tired-looking though they may be. However, the big story right now in the habitat garden is happening in the leaves: that giant munching sound you hear is the caterpillars feeding.

Bees nectaring on Echinacea, purple coneflower.

Bees nectaring on Echinacea, purple coneflower.

If you have read University of Delaware Professor Douglas Tallamy’s book “Bringing Nature Home”, you already know that most (about 96%) of our songbird species need insects as part of their diet. Lepidoptera (butterfly and moth) caterpillars are a large diet component of insectivorous birds. Summer is prime Lepidoptera season both for caterpillars and mature adults. Some of the best plants for supporting caterpillars, and thereby birds, also provide nectar and pollen for other pollinators, fruits or nuts for the birds, insects and other critters, shelter, nesting material and good places to raise babies.

This big juicy caterpillar could be food for a hungry bird in your garden.

This big juicy caterpillar could be food for a hungry bird in your garden.

So here are a few plant superstars to try in your wildlife garden:

Do you have room for a tree? Oak (Quercus species) trees are champion providers for native caterpillars at 518 species, but they also provide pollen in the spring for the bees, acorns in the fall and winter for squirrels and other critters, as well as shelter and places to raise babies for all sorts of birds, insects and mammals. Especially lovely specimens for your garden are the Willow Oak (Q. phellos), Scarlet Oak (Q. coccinea) and Swamp White Oak (Q. bicolor).

This northern pin oak will provide great wildlife value to your landscape, as well as fall color.

This northern pin oak will provide great wildlife value to your landscape, as well as fall color.

Do you have a native Cherry Tree? Our native cherries and plums (Prunus species) support 429 native caterpillar species. They also provide pollen and nectar in the spring and fruit in the summer enjoyed by both insects and birds. In addition to the Wild Black Cherry (P. serotina), others to try include the American Plum (P. americana), and for your beach home, the Beach Plum (P. maritima).

This American plum is a fine plant to add to your backyard habitat for native pollinators, fruit-eating birds, as well as insects that will eat the leaves, providing more food for birds.

This American plum is a fine plant to add to your backyard habitat for native pollinators, fruit-eating birds, as well as insects that will eat the leaves, providing more food for birds.

Don’t have room for a large tree? Try one of our native Dogwood (Cornus species) trees or shrubs. Not only do these plants offer pollen/nectar, fruits and foliage for the critters, they also are very attractive as landscape plants with lovely flowers, pretty fruit and attractive fall foliage color. Try our common Flowering Dogwood (C. florida), or one of the large shrubs such as Redosier Dogwood (C. serecia) or Silky Dogwood (C. amomum).  Another superstar shrub is the Blueberry (Vaccinium species), which supports 286 species of caterpillars. Just like the others, it also provides nectar and pollen for the bees, and fruits relished by the birds but in a much smaller size, including dwarf selections. It too has pretty spring flowers, attractive fruit and lovely fall color. Plant several named varieties for the best fruit set.

Here, a Unicorn Caterpillar feeds on a blueberry bush.

Here, a Unicorn Caterpillar feeds on a blueberry bush.

We also have some superstar herbaceous flowering plants. Members of the Aster Family (Asteraceae) are standouts for supporting Lepidoptera caterpillars with their foliage, especially Goldenrods (Solidago), Asters (Eurybia, Symphyotrichum), perennial Sunflowers (Helianthus) and the butterfly favorite, Joe Pye Weed (Eutrochium). Some are just beginning to bloom now while others will bloom in early and late fall, providing an important source of late-season pollen for the pollinators, as well as seeds for the birds.

A Meadow Fritillary feeds on nectar from a blooming goldenrod, which will begin blooming in early August.

A Meadow Fritillary feeds on nectar from a blooming goldenrod, which will begin blooming in early August.

So plant some of these superstars in your garden and then put out the all-you-can-eat buffet sign for your birds and critters!

By Derek Stoner, Conservation Project Coordinator and Sheila Vincent, Public Program Coordinator

A Monarch caterpillar munches on a milkweed leaf at Ashland. Photo by Hank Davis.

Right now, the last generation of Monarch butterflies in our region are completing their life cycles.  The Monarchs we are seeing now are likely three to four generations removed from their ancestors that arrived here in early summer.

Last week, photographer and DNS board member Hank Davis captured an amazing series of images of Monarchs in all different stages, all in one tiny island in the middle of the Ashland parking lot!

A Monarch caterpillar hangs upside down in a typical "J" shape prior to forming its chrysalis.

In late summer, the adult Monarchs lay their eggs on milkweed plants as usual.  The tiny egg (smaller than a pin head) hatches after 5-7 days, and the caterpillar that emerges will feast on milkweed for 10-14 days.  When the caterpillar is mature enough (the final instar or stage), it will seek out a sturdy stem to hang from and curl up in  a “J.”

A freshly-formed Monarch chrysalis hangs from a goldenrod stem. Photo by Hank Davis.

The magnificent chrysalis is actually the last skin that the caterpillar will wear, and where it will spend the next 10-15 days transforming into a butterfly.

A Monarch chrysalis "ready to hatch" with the dark orange wings of the adult butterfly visible inside. Photo by Hank Davis.

The hardened skin of the chrysalis is an opaque pale green color until it is time for the adult Monarch to emerge.  Then the skin becomes becomes transparent and the butterfly breaks free.

After the adult Monarch emerges, all that is left is the paper-thin chrysalid case. Photo by Hank Davis.

The abandoned chrysalis looks and feels like tissue paper, and retains the wondrous gold and black speckling ringing the top.

This is how the next generation of Monarchs starts: a mated pair of Monarchs. Image by Derek Stoner.

The adult Monarch will hang for hours drying its wings, and finally set forth on its first flight to find nectar sources.  The twist, however, is that this generation is “programmed” to migrate south all the way to ancestral wintering grounds in the mountains of central Mexico.  How do they accomplish this amazing feat?  We don’t know the full answer!

If you’d like to learn more about Monarchs and explore their world, we invite you take part in the Monarch Migration Celebration this Saturday, September 18, from 10:00am to Noon, at the DuPont Environmental Education Center in Wilmington.  

On Saturday, September 25, from 2:00 to 4:00pm, families can take part in the Monarch Migration program at Burrows Run Preserve, where we will capture, tag, and release Monarchs on their way to Mexico.

For more information about these programs, please visit www.delawarenaturesociety.org.

By Derek Stoner, Conservation Project Coordinator

A Sleepy Orange butterfly at Middle Run Natural Area, 8/23/10. Photo by Hank Davis.

As late summer rolls along, there is a great deal of movement in wildlife populations.  We often think of the songbirds starting to move south and the Monarch butterflies beginning their long voyage to Mexico, but sometimes there are strange exceptions to the “head south as fall begins” rule. 

This week at Middle Run Natural Area, our birding group made a unique discovery of an uncommon butterfly from the south.  A Sleepy Orange, a member of the sulphur family related the our familiar Clouded Sulphur, appeared along the trail and its brilliant orange upperwing  captured our attention.  Hank Davis snapped some great photos to document this unusual find.  After consulting the field guides, we all had a “life” butterfly to add to our lists.   The Sleepy Orange is only rarely seen in our region in late summer, and thus becomes a prize find for us naturalist-types.

A Hickory Horned Devil Caterpillar at Middle Run, August 23, 2010. Photo by Hank Davis.

Another interesting insect that we came across is this Hickory Horned Devil caterpillar.  Nearly four inches long  and thick as a finger, this creature with the sinister-looking antenna still has a lot of growing to do.   These guys top out at six inches long and will turn a blue-green when they reach they final instar stage of caterpillar-hood.  Hickory Horned Devils are harmless, but they sure are a monstrous caterpillar! 

If you are interested in insects, join us for the second-annual Middle Run Bio-Blitz this Saturday, August 28, from 8:00am until early afternoon.  We will search for butterflies, dragonflies, bees, and other six-legged creatures.  Join in the fun at Middle Run!  We will meet in the main parking lot off of Possum Hollow Road.