Saturday, May 3, 2008

Monarch Migration

Coming soon to a Milkweed near You

The northward migration of the Monarch has been underway here in Texas for some time. Be on the lookout in the North Country, they are coming your way. They typically advance northward in the Spring as larval host plant (Milkweed being most common) becomes available for the caterpillar.

Monarch – Danaus plexippus
(Remember to click on the Photographs)
Photographed nectaring on Purple Coneflower – Echinacea sp.
Ft. Worth Botanical Gardens

Echinacea, commonly called Purple coneflower, is a genus of nine species of herbaceous plants in the Family Asteraceae. All are strictly native to eastern and central North America. The plants have large showy heads of composite flowers, blooming from early to late summer. Some species are used in herbal medicines.

Monarch – Danaus plexippus
(Male - Note the scent glands on the hindwing)
Photographed in south Texas on Mist flower - Eupatorium coelestinum

Eupatorium has at times been held to contain as many as 800 species, but many of these have been moved (at least by some authors) to other genera, including Ageratina, Chromolaena, Condylidium, Conoclinium, Critonia, Cronquistianthus, Eutrochium, Fleischmannia, Flyriella, Hebeclinium, Koanophyllon, Mikania, and Tamaulipa.

The classification of the tribe Eupatorieae, including species placed in Eupatorium in the present or past, is an area of ongoing research, so further changes are likely. What seems fairly certain by now is that the subtribe Eupatoriinae seems a good monophyletic group containing Eupatorium and the Joe-pye weeds (Eutrochium), and possibly others. (1)

Monarch Caterpillar
(Click for a great look at these wonderful caterpillars)
Photographed at the Ft. Worth Nature Center

The caterpillars are feeding on vining milkweed. The two on the left are hanging head down on the vine stem while eating the milkweed leaf.

A very similar butterfly seen in South Texas is the Soldier. In the wings-folded position, it is easily recognized by the “smeared” pattern of the veining on the hindwing. The Soldier is also called the Tropic Queen.

Soldier – Danaus eresimus
Photographed near McAllen, TX

Additional information for those interested in the
Reproductive stages of the Monarch

The mating period for the overwinter population occurs in the spring, just prior to migration from the overwintering sites. The courtship is fairly simple and less dependent on chemical pheromones in comparison with other species in its genus. Courtship is composed of two distinct stages, the aerial phase and the ground phase. During the aerial phase, the male pursues, nudges, and eventually takes down the female. Copulation occurs during the ground phase and involves the transfer of a spermatophore from the male to the female. Along with sperm, the spermatophore is thought to provide the female with energy resources that aid her in carrying out reproduction and remigration. The overwinter population returns only as far north as they need to go to find the early milkweed growth; in the case of the eastern butterflies that is commonly southern Texas. The life cycle of a monarch includes a change of form called complete metamorphosis. The monarch goes through four radically different stages:

  1. The eggs are laid by the females during spring and summer breeding months.
  2. The eggs hatch, revealing worm-like larva, the caterpillars. The caterpillars consume their egg cases, then feed on milkweed, and sequester substances called cardenolides, a type of cardiac glycosides. During the caterpillar stage, monarchs store energy in the form of fat and nutrients to carry them through the non-feeding pupa stage.
  3. In the pupa or chrysalis stage, the caterpillar spins a silk pad on a twig, leaf, etc, and hangs from this pad by its last pair of prolegs. It hangs upside down in the shape of a 'J', and then molts, leaving itself encased in an articulated green exoskeleton. At this point, hormonal changes occur, leading to the development of a butterfly. The chrysalis darkens (actually becomes transparent) a day before it emerges, and its orange and black wings can be seen.
  4. The mature butterfly emerges after about two pupal weeks and hangs from the split chrysalis for several hours until its wings are dry (often in the morning). Meanwhile fluids are pumped into the crinkled wings until they become full and stiff. Some of this orangy fluid drips from the wings. Finally (usually in the afternoon) the monarch spreads its wings, quivers them to be sure they are stiff, and then flies in a circle and away, to feed on a variety of flowers, including milkweed flowers, red clover, and goldenrod.

Monarchs can live a life of twenty to eighty weeks in a garden having their host Asclepias plants and sufficient flowers for nectar. This is especially true if the flower garden happens to be surrounded by native forest that seems to be lacking in flowers. (1)

(1) Reference: WikiPedia

Troy and Martha



Louis la Vache said...

These Monarch photos bring back memories! "Louis la Vache" grew up in Lubbock. He remembers one summer - 1957(?) - great swarms of Monarchs migrating through Lubbock. Louis got a net and a jar with a cotton pad and formaldehyde and started a collection of Monarchs.

judi/Gmj said...

Thanks for knocking out the varification step. :) When we lived in Ok. we were just behind you in the migritory path. They would show up in waves. Filling the trees and resting a little while, and move on. No so in the Pacific Northwest. Just a few show up here. I miss them and thank you for sharing.

Stacey Olson said...

Great photos and such helpful information. I always learn so much on these blogs it is just amazing.. thanks

Duncan said...

Very interesting post Troy ad Martha, we have the Monarch over here, a natural introduction, but they've been very scarce the last few years. Maybe drought related. Sounds as if the plant taxonomists are making life difficult for you as well!!

Janet said...

Beautiful collection of butterfly photos!

John B. said...

I haven't seen any Monarchs yet, but I'm sure they will be around soon enough. The coneflowers have not bloomed yet.

imac said...

Natures Beautiful Creatures, and captured fantastic, along with all the info certainly makes a 1st class post.

Thanks for visiting my blog and your kind comments.

Doug Taron said...

Most of the Monarchs that arrive here in Chicago each spring were born down in your neck of the woods. On very rare occasion, a monarch will continue flying northward and make it all the way up here from Mexico. This is apparent because they arrive weeks ahead of the main influx of MOnarchs, and they are very faded and worn looking. I have seen exactly two that fit that description. Coincidentally, the second was just this past Friday, on Chicago's lakeshore.

Marvin said...

So far this year I've seen a few butterflies that could have been Monarchs, but they wouldn't slow down long enough for me to tell for certain. Their host plants are not yet blooming up here on the ridge, but could be down in the valleys.

Thanks for the very informative post.

Joe said...

We have a small butterfly garden and the Monarchs lay lots of eggs on the Milkweed. We see lots of Monarch caterpillars!