Saturday, June 15, 2013

Candystore of Caterpillars

That's how I described my day in the Klickitat River Canyon on June 1 when telling my parents about it.  Seemed like every time I turned around I found another caterpillar!  Mourning Cloak (Nymphalis antiopa) larvae covered many of the willows along the river, most were over 2 inches long (5th/final instar), but there were a few clusters of mid-instar larvae around an inch long.  Bushes of Gray's desert parsley (Lomatium grayi) held several late-instar Anise Swallowtail (Papilio zelicaon) larvae and two Indra Swallowtail (P. indra) larvae.  Several California Tortoiseshell (Nymphalis californica) larvae were found on deerbrush ceanothus (Ceanothus integerrimus), and Elegant Sheepmoth (Hemileuca eglanterina) larvae were found on snowberry (Symphoricarpos albus).  I found several eggs on lupine flower spikes that were either Arrowhead (Glaucopsyche piasus) or Silvery (G. lygdamus) blues, two Silvery Blue larvae on lupine seed pods, and an egg on Lathyrus (pea, not sure of species) that I believe is a Northern Cloudywing (Thorybes pylades) that I am now rearing on American vetch (Vicia americana).
During the following week when I was at the Sinlahekin Wildlife Area, I found several masses of early/mid-instar Milbert's Tortoiseshell (Aglais milberti) larvae and one 5th instar Satyr Anglewing (Polygonia satyrus) larvae, all on stinging nettle, along with another Northern Cloudywing egg on American vetch and several 1st instar Anicia Checkerspot (Euphydryas anicia) larvae on Chelan penstemon (Penstemon pruinosus).
A friend of mine asked how in the world I find all this stuff, particularly the eggs. It's sort of a mix of probability, intuition, and knowing the host plants and life stage of different species at different times of year.  For example, I knew that Anise Swallowtails use many species of Lomatium along with other species in the carrot/parsley family, and that Indra Swallowtails specifically prefer Gray's desert parsley.  Both swallowtail species fly fairly early in the spring, so their larvae should have been on those plants this time of year.  Anise Swallowtail caterpillars are bright green with black bands and yellow or orange spots, and are pretty easy to pick out against the feathery green leaves of Gray's desert parsley.  However, my mind was focused on that image so I completely missed the two tiny black Indra larvae that Ben found!
Anise Swallowtail (Papilio zelicaon) larva on Gray's desert parsley (Lomatium grayi) along Klickitat River
Anise Swallowtail (Papilio zelicaon) larvae - orange-spotted form (left two) and yellow-spotted form (right)
Pre-pupal Anise Swallowtail larva (left) and pupa/chrysalis (right, brown form)
The smaller Indra larva died a couple days later from refusing to feed on dill or fennel (a risk I took as Indra are picky eaters compared to Anise Swallowtails which eat nearly anything in the parsley family).  The larger larva seemed to be doing alright on dill, but died a week later possibly from a bacteria or virus that also attacked one of the four Anise Swallowtail larvae I brought home.
Indra Swallowtail (Papilio indra) larvae, L1/L2 @ 5mm (above), L3 @ 13mm (below)
Most species of blues have been flying for a few weeks now, or are beginning their flights, so eggs and larvae can be found now, usually on legumes.  Silvery and Arrowhead blues tuck their eggs in between the unopened buds of lupine and occasionally on the flowers or seed pods.  Boisduval's Blue (Plebejus icarioides) primarily lay their eggs on the underside of lupine leaves.  Larvae of these species can be found in the same locations.
Arrowhead Blue egg on lupine buds at the Sinlahekin (left) and Boisduval's Blue egg on lupine leaf near Klickitat (right)
Silvery Blue larva, new pupa with shed larval skin (upper left) and mature pupa (upper right), all are the same individual found on lupine near Goldendale.
Purplish Coppers (Lycaena helloides) feed on dock (Rumex sp.), smartweed (Polygonum sp.) and other related species, and their eggs and larvae are often easily found on these plants.  In some cases the plants are literally sprinkled with eggs!
Purplish Copper eggs on smartweed (Polygonum sp.) at Fish Lake, Sinlahekin Wildlife Area
A couple years ago I discovered a colony of Northern Cloudywings at the Sinlahekin, and observed the females laying eggs on American vetch (Vicia americana) and cream pea (Lathyrus ochroleucus).  The eggs are relatively large (~1mm) and white, making them rather conspicuous on the underside of leaves.  When I saw a pea/vetch-type plant in the Klickitat River Canyon I flipped over a few leaves and found the egg shown here.
Northern Cloudywing egg (from Sinlahekin, left) and hatching/hatched egg (from Klickitat, right)
Northern Cloudywing larva (from egg found near Klickitat) with approximate larval instar (L#) and length. Click on photo to view at full-size.
As mentioned before, I located the hostplant of Anicia Checkerspots at the Sinlahekin this year: Chelan penstemon. Checkerspot larva usually build web nests similar to tent caterpillars.
Anicia Checkerspot eggs and newly-hatched larvae (upper left) and 2nd instar larvae.  Chelan penstemon in inset.
I always check any nettle I find for larvae of Milbert's Tortoiseshell (Aglais milberti), Satyr Anglewing (Polygonia satyrus) and Red Admiral (Vanessa atalanta).  Milbert's lay their eggs in masses, and the caterpillars feed together until later instars when they build individual nests, compared to the other two species which lay 1-3 eggs at a time and the larva feed singly.  There will always be some exceptions, but it has been my experience that Milbert's tend to make leaf nests with the leaf folded upward, while Satyr Anglewing and Red Admiral larvae fold the leaves downward.
Milbert's Tortoiseshell larvae (L4) on stinging nettle at the Sinlahekin
Milbert's Tortoiseshell larvae (L4 with some tiny L2 near the center) on stinging nettle at the Sinlahekin
Milbert's Tortoiseshell larvae (L3) on stinging nettle at the Sinlahekin
Satyr Anglewing larval nest (top, note leaf folded downward), L5 larva (center and bottom) and pupa (right)
Finally, here are some photos of the Mourning Cloak larvae we were finding all over the willows along the Klickitat River.  I brought four of the larvae home and all pupated within three days.  One was parasitized; the chrysalis appeared dead yesterday and today there is a hole in it and some kind of fly pupa in the cage.  Oh! and how appropriate, I just glanced over at my bug cage and noticed the first butterfly has emerged! So lets end this post with my favorite butterfly...
Mature (L5) Mourning Cloak larvae on willow along the Klickitat River, June 1
Mourning Cloak
Cluster of L4 (~1 inch) Mourning Cloak larvae on willow
More L4 Mourning Cloak caterpillars
Pre-pupal larva and two pupae - they all insisted on attaching themselves to the zipper of my cage, so I had to tape the silk to sticks.
Newly-emerged Mourning Cloak!

1 comment:

  1. I thought I'd check out your blog. One thing I was pleased to see was the both the (tent) nest of Polygonia satyrus and at least one instar of larva and the distinctive group nesting of the Milbert's Tortoiseshell. When I first started studying all of our Nettle feeders, maybe 16 years ago, I was pleased to note that one could find and identify larvae by the unique nesting form, and I didn't think enough of the literature focused on what you see in the field when you are looking for caterpillars.