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Let’s celebrate National Moth Week with a post on the Big Poplar Sphinx! Pachysphinx occidentalis begin life by exiting eggs left by the mother moth on leaves of a sheltering plant. They will go through metamorphosis in shallow burrows underground. Before becoming moths, they are the cliche green caterpillars everybody loves. The larvae will feed on cottonwood.
These moths can be seen flying in Alberta and North Dakota, all the way to Washington, Texas, Arizona, southern California, and Baja California Norte. 
Certain moths have an extra sense most don’t know about. It’s an olfactory sensitivity that is almost considered supernatural. They have the ability to detect a single molecule of female sex hormones from miles away. These molecules are called pheromones. Males in the Saturniid, Bombycid, and Lasiocampid families have large, feathery antennae with a broad shape. This shape allows air to come in contact with them quite frequently, in turn allowing the hair-like olfactory receptors, which group together on the antennae in great quantities, to detect even the slightest of these chemical stimuli. Female moths are perfectly aware of this talent, and emit an odor that has been known to call males from up to 11 km (about 7 mi) away. Just imagine trying to detect one molecule of scent from one cubic yard of air. That’s virtually undetectable for humans, yet up to 100 male moths can not only smell it, but lead themselves to the source of it. 
Photo credit: smccann