Saturday, September 6, 2014

Western Tent Caterpillars

Going back through my photos from this summer, I was reminded of the local tent caterpillar infestation and thought it might be useful to answer some of the questions I heard at the time.  The infestation was so large that it even made it into the local news:
Caterpillars setting up camp in Columbia County
Caterpillars invading Washington side of the Columbia too
During the summer, I rode my bike about once a week in an area west of Longview/Kelso, which was in the area infested with tent caterpillars, and on June 18th I noticed caterpillars covering the road and bushes, and then realized many of the alder trees along the forest road were nearly defoliated!  When I stood quietly and listened, it sounded like it was raining even though there were no clouds in the sky...it was the sound of all the droppings of millions of caterpillars falling through the trees and bushes, gross but fascinating!
Western Tent Caterpillars during an outbreak west of Longview/Kelso
There are many moth species with larvae that feed in communal groups and spin large webs or "tents" for protection, and are therefore known as tent caterpillars or webworms.  The most common species in our area is the Western Tent Caterpillar, Malacosoma californicum (see here for photo of adult and more information).  The Western Tent Caterpillar usually goes unnoticed, with only a few tents scattered high up in deciduous trees, but occasionally goes through a period of epidemic outbreaks, such as we saw this June.  Another large outbreak occurred in the Mt. St. Helens area in 2011 and 2012, where they completely defoliated alder trees.  These outbreaks usually end after one or two years because of viruses and/or lack of food.  Even if the trees are completely defoliated, they are rarely killed because of the relatively short period of the outbreak.  In the area west of town that I mentioned, the alder trees were already leafing out again less than two months after the caterpillars stopped feeding and pupated.
Mostly-defoliated alder trees west of Longview/Kelso on June 18th
Although alder trees are the favored food source of Western Tent Caterpillars in this area, they will feed on nearly any deciduous trees and shrubs, often switching to maples, poplars, fruit trees and berry bushes when they've consumed all the alder in the area.  By the time this occurs however, the caterpillars are usually in the final stage of development and only have around one week before they pupate and turn into adult moths.  At 1 1/2 inches, the caterpillars are also more noticeable in the final stage, and seem to appear out of nowhere because up until this point they have spent most of their time high up in the trees and out of sight.
Defoliated (left) and mostly-untouched (right) alder trees west of Longview/Kelso on June 18th

Thursday, July 10, 2014

First Monarch Caterpillar!

During my recent trip to the Sinlahekin Wildlife Area, I discovered my first Monarch caterpillar! Shortly afterward, my mom found a second one nearby, which I brought home to rear, as it was slightly larger than the one I found and I didn't want to risk taking both if I couldn't find enough milkweed to keep them fed.
He has gone from just over 1/4 inch long to over 1 inch long in one week!  Also while up north last week, I took advantage of being in the area and visited Long Swamp for the first time.  It is a place I've been curious to see, especially as it hosts the Freija Fritillary, which is only recorded in a small area of northern Okanogan County in Washington (most of it's range is in Canada).  Long Swamp is only about 15 straight-line miles from the Sinlahekin, but is at about 6,000 feet elevation, so has a suite of higher-elevation/sub-alpine butterfly species not found at the Sinlahekin.  I was able to collect my first Freija Fritillary (Boloria freija), a nice fresh male, and also saw numerous Vidler's Alpines (Erebia vidleri) and Anna's Blues (Plebejus anna).
I'm about to head down to the Lepidopterists' Society annual conference in Utah next week and don't have much time to report about my trip to the Sinlahekin just yet, so there will be lots to catch up on when I get back!
For now, here are some photos of Mr. (or Ms.) Bugaboo...
My first Monarch caterpillar!
Mom's first Monarch caterpillar (the one I brought home)
Mr. Bugaboo, three days after bringing him home (~3/4 inch)
What he looks like today, at a little over 1 inch long

Monday, June 30, 2014

Weekend of Butterflies at the Sinlahekin!

This coming weekend I'll be leading a series of butterfly field trips at the Sinlahekin Wildlife Area (northern Okanogan County, Washington) as part of their 75th Anniversary Celebration this summer.  I've been frantically editing several hundred photographs over the past few weeks and finally finished several pages for a condensed field guide of Sinlahekin butterflies that I will hand out to participants this weekend.  I'm so thrilled to have finished it that I want to share part of it here. Sorry about the copyright watermark but because this will be part of a larger self-published book, I don't want it being circulated without credit... you'll have to come on a field trip if you want a clean copy :) and yes, there's a typo on the first page, I fixed it but don't have time to re-export these images for my blog at the moment.
The weather will be great for butterflies, but it's going to be hot so if you are planning to participate, bring lots of water!  There will be several nets available if anyone wishes to use them during the field trip, but we will be visiting several places that should provide good photo-ops of butterflies on mud and flowers, and hopefully some caterpillars.
Visit the WDFW page for more info on this and other events:
http://wdfw.wa.gov/lands/wildlife_areas/sinlahekin/75thanniversary.php



Sunday, June 8, 2014

Species Profile: Margined White

Margined Whites range throughout most of western Washington, with scattered populations in the northeast and southeast corners of the state.  They are one of the first butterflies to appear in the Spring in Western Washington, and are common along forest roads and wooded rural areas.  Margined Whites are often mistaken for their introduced European cousin: the Cabbage White.  On May 1 of this year, I found some Margined White eggs on a native bittercress (likely Cardamine angulata) in the Mosquito Creek area northwest of Longview, WA. I brought three of the eggs home and all three hatched three days later.  Only one of the larvae survived to adulthood, and it emerged yesterday, June 7.  During another trip to Mosquito Creek on May 22, I found a 1st instar larva on the same plants where I found the eggs, and brought it home.  It is in the final (5th) instar right now and should be pupating soon.  I reared both larvae entirely on garden cabbage (young plants I purchased from a garden center).
Margined White (Pieris marginalis)
Description
Wingspan: 38 to 57 mm
Male: white above and below, sometimes with yellowish tint.  Veins usually lined with gray to greenish-gray, especially on VHW.  Spring form has more gray on dorsal wings.
Female: slightly heavier gray markings.
Egg: yellowish white.
Larva: bright green covered with tiny white and dark green speckles and faint stripes.
Pupa: greenish yellow to tan.
Similar Species
Cabbage White (Pieris rapae) almost always has one or two black spots on DFW and black FW apex, and lacks the dark wing veins on the VHW.  Some forms of Margined White lack strongly-marked VHW veins and may have faint black DFW spots similar to Cabbage Whites.  Margined Whites tend to be more common in woodlands and forest edges, while Cabbage Whites are more common in disturbed habitats.
Habitat & Biology
Habitat: woodland edges and clearings, riparian areas and forest road corridors.
Overwintering stage: pupa.
Larval host:  native crucifers, including rockcress (Arabis spp.) and bittercress (Cardamine spp.).
Adult food source:  many flowers, including mustards, dandelions, asters, daisies, cinquefoils, and salmonberry.
Flowers of plant (likely Cardamine angulata) that eggs were found on.
Leaf of plant (likely Cardamine angulata) that eggs were found on
Margined White (Pieris marginalis) egg on Angled Bittercress (Cardamine angulata)
Newly-hatched larva (L1) of Margined White (Pieris marginalis)
Late L1 (first instar) larva of Margined White
Freshly molted L2 (second instar) larva of Margined White
Late L2 (second instar) larva of Margined White
Freshly molted L3 (third instar) larva of Margined White
L4 (fourth instar) larva of Margined White (head is facing down)
L4 (fourth instar) larva of Margined White (head is on left)
L5 (fifth instar) larva of Margined White (head is on right)
Newly-formed pupa of Margined White
Pupa (4 days old) of Margined White - note the small white patch of the wing forming
Pupa (4 days old) of Margined White
Pupa (8 days old, 3 days before emergence) of Margined White
Empty pupa after emergence of adult Margined White
Newly-emerged male Margined White

Saturday, May 10, 2014

Painted Lady migration

There have been numerous reports of Painted Ladies (Vanessa cardui) making their way north through Washington the past couple weeks.  The Painted Lady usually can't survive our winters and must migrate here from warmer regions in the southern states.  Depending on weather and population conditions, some years we may never see any Painted Ladies here, while other years they will be everywhere.  I haven't seen very many at all for the past couple years, but this year have already spotted two near Longview, and others have spotted them in places around Seattle, Ellensburg, and Spokane.  They are very fast and wary butterflies, often hard to catch or photograph.  Their larvae feed on thistles, so keep an eye out for spiny, lavender-gray caterpillars and shiny gold chrysalids whenever you see a patch of thistles!
Painted Lady Vanessa cardui - dorsal side
Painted Lady Vanessa cardui - ventral side
A cousin of the Painted Lady, the Red Admiral (Vanessa atalanta), is another butterfly that usually cannot survive our winters and must migrate here from warmer climates, although occasionally a lucky few will survive in garages or other protected areas.  Their larvae feed on stinging nettle, and form folded-leaf tents that I have described in a previous blog post (see here).  Red Admirals have been spotted near Yakima recently.
Red Admiral Vanessa atalanta - dorsal side

Red Admiral Vanessa atalanta - ventral side