When I first came to Arizona, I loved the heat...that was in late September when we went hiking at Apache Trails. After living here for a year, I realized that summer is really not meant for outdoor activities when you are in the southwest desert. The weather have been unbearably hot since I got back from Mexico in July.
This weekend, the morning temperature loom below 90oF, at approximately 35oC. We decided to go for a short hike at South Mountain, Phoenix. South Mountain has lots of short trails and a lovely view of the city of Phoenix. It is also only a short distance away from Tempe so we didn't have to drive too far.
We hiked the Mormon Trail this time, which is a rocky trail with several valleys and peaks along the trail. Halfway through the trail, we started seeing lots of yellow caterpillar. It became quite a creepy trail after a while when you stop to look around and these caterpillar is all around you (at least for me lah). They are about 2-3 inches long and is as fat as my index finger. The worst is climbing up a rock and looking up into a big fat one. Eeeeck!!
Why are they all over the place?? What are these yellow caterpillar?
These caterpillars are called white-lined sphinx caterpillar (Hyles lineata). They are quite pretty with bright yellow color and black lines/spots (when I don't have to be hopping around avoiding them lah). They all seems to be moving towards the same direction - North but I don't think it is an organized colony migration, rather individual migration that appears like colony migration because there are so many of them!! It is unclear why they are migrating. The two hypotheses on why they are migrating at this time are:
1) It is time for them to pupate and they need to burrow into moist soil. Desert mountain soil has high clay content and are hard to dig into for burrowing.
2) With lack of rain in the summer, they are starting to run out of their food source = desert weed plants, and so they migrate to search for food. You might find them in your backyard!
Hopefully they will find a safe place to pupate and in a few weeks, we'll see the white-lined sphinx moth!
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