This Week's Update Includes:

• News: Crossing into Mexico!
• News from Mexico: Monitoring Begins
• Slideshow: Too Cold to Fly?
• The Migration: Maps and Journal

"With the arrival of Cold Front Number 5 to our beloved Mexico, the awaited monarch butterflies have arrived in Ciudad Acuna!"

Pulse Appears in Texas
At the same time, many observers reported a clear pulse arriving in Texas, where monarch numbers have been unusually low.

Gregg Lee was seeing only a few monarchs per day on nearly 10 acres of blooming Liatris. Things changed on Monday: "Monarchs were on every patch I checked, in some areas with one every 5 or 10 feet. A total of 500 is a safe estimate." 10/8/12 Chalk Mountain, TX

The pace picked up to 53 monarchs per hour in Keene, TX: "Most are flying above the tree tops, a few coming down to our yard to rest." 10/10/12 Patty Lockwood

Largest Roost in Texas
Only seven roosts have been reported so far from Texas, containing a total of 350 butterflies. Let's hope for more like the one on Tuesday night with its estimated 2,000 butterflies:

"It was a good crop of monarchs, in clusters by the dozens (2-4 dozen per cluster) on scattered tree branches in a small pecan grove," reported Genie Robinson from Brackettville.

Appalachians Peak
In the East, the excitement continued along the Appalachian chain:

"While on the playground to release a monarch we had raised, our class observed 21 other monarchs in flight. We just completed our Symbolic Monarch Migration packet. What a special day for this class of first graders!" 10/4/12, Knox Elementary, Canton, Georgia

While driving on North Carolina's Blue Ridge Parkway, Rachel and her 11 year-old daughter came upon a river of butterflies flowing at 400 monarchs per minute. "They were everywhere!" 10/2/12

"After a long walk, we saw no trace of a single monarch, so Jocelyn and Roberto marked zero on the monitoring graph," Estela Romero reported on Monday from Angangueo in English and Spanish.

• Slideshow: Too Cold to Fly?