BajaNomad

yellow butterfly migration

vandenberg - 9-27-2016 at 05:31 PM

Every end of September, beginning of October we witness the mass migration of millions of small yellow butterflies. They always travel east to west. Since they must mate and lay eggs somewhere between Loreto and the ocean they must land somewhere, mate and lay eggs to puppate and turn into butterfly offspring.
Question: How come we never see those critters returning east at any time of year in the same masses as they arrived in Sep/Oct. Have been wondering about this for 3 decades and thought it be time for my knowing Nomad friends to finally answer my question.
So, where are they coming from and where are they settling and then how come they don't go east in the same quantities with which they arrived.?

DaliDali - 9-27-2016 at 05:51 PM

Flying north to south in my neck of the woods.

They damn well better not munch my tomato seedlings......

AKgringo - 9-27-2016 at 05:54 PM

I don't know anything about their life cycle, but in early November of 2014 they were washing up by the millions on some of the beaches along the road to San Juan de la Costa. That is the mine town north of El Centennario and La Paz.

Skipjack Joe - 9-28-2016 at 07:00 AM

http://forums.bajanomad.com/viewthread.php?tid=62507

danaeb - 9-28-2016 at 08:42 AM

Cloudless Sulphur:

http://entnemdept.ufl.edu/creatures/bfly/bfly2/cloudless_sul...

SFandH - 9-28-2016 at 08:43 AM

I saw swarms, thousands and thousands, of little yellow butterflies flutter by my campsite at Santispac once. It went on for an hour or so. Love stuff like that.

Skipjack Joe - 9-28-2016 at 09:44 AM

Quote: Originally posted by danaeb  
Cloudless Sulphur:

http://entnemdept.ufl.edu/creatures/bfly/bfly2/cloudless_sul...


A good read.

willardguy - 9-28-2016 at 11:31 AM

be sure to top off the windshield wiper fluid!

Russ - 9-28-2016 at 01:41 PM

They showed up her this afternoon in a constant stream.

redhilltown - 9-30-2016 at 12:11 AM

I have sat on a secluded beach near Black Mountain (north of Five Island) and watched a little highway of them travel east to west. Love it.

vandenberg - 9-30-2016 at 08:01 AM

But..back to my original question...it can't be a one way migration, so when is the return trip and how come we don't notice it?

danaeb - 9-30-2016 at 08:24 AM

Maybe this?

"There are different reasons why butterflies will migrate toward other places. Did you know that all butterflies are cold-blooded creatures? They simply can not handle the colder weather so have to travel somewhere warmer. They also need to stay where their food source is – if it’s winter and there are no flowers, they can not stay there.

If weather changing is not a problem, like for the butterflies in the tropics, butterflies will often migrate away in order to establish new colonies. The reason for this is that if they stay in one place for too long, the butterfly caterpillars will consume all of their food in that one area, and so the butterflies will starve to death. So migrating to new places will ensure their survival and their food source."

- See more at: http://www.thebutterflysite.com/butterfly-migration.shtml#st...
Quote: Originally posted by vandenberg  
But..back to my original question...it can't be a one way migration, so when is the return trip and how come we don't notice it?

Pescador - 9-30-2016 at 08:54 AM

According to a friend who is a butterfly and moth specialist. These are not true Cloudless Sulphur. Instead they are a type of Sulphur that live and breed in the Baja region. When we have dry years, they will not come out of the cocoon and may be dormant for several years, but when you get a hurricane in the region, the low pressure triggers their transformation so they come out of the cocoon, eat like crazy, (hence all of the caterpillars who eat everything in sight, then metamorphasize into butterflies, which lay eggs and start the cycle all over again. Mostly we see these following major hurricanes.
One year the highway was a real mess as the caterpillars were eating all the vegetation along side of the highway but when they would cross, they would do so in droves, so the road became kind of a gooey slick. Trucks that year were all sporting screens on the grilles and had to stop every so often and clean the grills.

BornFisher - 9-30-2016 at 09:27 AM

Going for a new bumper sticker---
"I Brake For Butterflies and Caterpillars"

Skipjack Joe - 9-30-2016 at 10:24 AM

Quote: Originally posted by vandenberg  
Every end of September, beginning of October we witness the mass migration of millions of small yellow butterflies. They always travel east to west. Since they must mate and lay eggs somewhere between Loreto and the ocean they must land somewhere, mate and lay eggs to puppate and turn into butterfly offspring.
Question: How come we never see those critters returning east at any time of year in the same masses as they arrived in Sep/Oct. Have been wondering about this for 3 decades and thought it be time for my knowing Nomad friends to finally answer my question.
So, where are they coming from and where are they settling and then how come they don't go east in the same quantities with which they arrived.?


Why would you expect the same number of butterflies to go in one direction as in another? All animals migrate to an area where there his more food and have their offspring with those extra nutrients. Then when conditions get worse the new population with the offspring fly back to more suitable climates. That's with birds, but it's similar for everything, from wildebeests to butterflies. At one end of the route you have offspring and multiply, at the other end you try to survive until conditions get good in the land of plenty. So the migration of butterflies in the west direction contain the offspring of 'a summer of love' and the reverse direction are the adults that remain after a full winter. It appears to be a migration in one direction because the reverse migration is sparse. I don't know what the procreation rate is but it's likely that each adult gives rise to numerous young.

That's my theory.