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Monarch caterpillar and frass

Danaus plexippus


Monarchs start as tiny stripped caterpillars so small you can barley see them on the milkweed plants they feed on. They go through five instars or growth phases while they are caterpillars gong from as small as 2mm to as big as 45mm during the 2 weeks they are in the caterpillar stage. This caterpillar is nearing the end of this phase of its life and will soon move away from the milkweed to attach itself to something and go into it's chrysalis phase.


Monarchs can be found all over the US and into Canada and Mexico. This one is living in my urban garden on the milkweed I've planted to encourage Monarch reproduction.


I'm giddy to report that I think this is the first PN spotting of Monarch poop! (Bug poop is actually called frass). I was watching this caterpillar eating milkweed leaves and saw her/him poop twice!

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Tukup a year ago

I was hoping you'd tell us what "frass" was :-) I was still thinking it was a typo for "grass." I don't know if I'd be "giddy" about it, but I sense a "Project Noah Mission: Poop ID" coming on. Great spotting(s) :-)

Wowwwww,,, wonderful!

Leuba Ridgway
Leuba Ridgway a year ago

Great story and photos on the poop ! A bit of physiology only adds to the spotting !!

AshleyT a year ago

Your spotting has been nominated for the Spotting of the Week. The winner will be chosen by the Project Noah Rangers based on a combination of factors including: uniqueness of the shot, status of the organism (for example, rare or endangered), quality of the information provided in the habitat and description sections. There is a subjective element, of course; the spotting with the highest number of Ranger votes is chosen. Congratulations on being nominated!

maplemoth662 a year ago

una hermosa oruga....

Ava T-B
Spotted by
Ava T-B

San Diego, California, USA

Lat: 32.72, Long: -117.11

Spotted on May 27, 2018
Submitted on May 27, 2018

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