In the Glow of the Night

On 6/7/13, KG, PB and I led our annual hike to Monte Bello, hoping for glowworms.  We had 17 participants. The hike was scheduled to start at 5:45; the last party caught up to us around 6:30. We looked at coyote brush for some casebearer moth bags, native ant nests, and listened to the Grasshopper Sparrows, one of which perched on some dead branches. Yellow Mariposa lilies punctuated the oats. Face flies were somewhat annoying; it was quite warm (80F at 9:00).

We stopped at the sag pond briefly, then continued down the hill. Darkling beetles, yet another dead fence lizard in the middle of the trail, a velvet ant, and pudgy jumping spider kept us busy. Along the way, we looked for large spider burrows. We showed the participants the small trapdoor spider hole that we refound on our scouting trip.

At the gravel pit, the blooms were gone from the jewelflower. White mariposa lilies had appeared since we were there last. We had time, so we went all the way up to our previous dinner spots on Indian Creek. It was still warm enough to stay in short sleeves at 8:00. Sunset was at 8:30, and we had time before it was dark enough to start looking, so we had a glowworm lesson, then started down slowly at 8:50.

PB had gone down earlier to place the LED lure. When we got close, I went ahead to check it. I didn’t see anything obvious going on, so I moved it from the side of the trail to the middle, closer to the edge of the canopy and sky. In a couple of minutes, five males showed up, and I called the group down. By the end of the 15 minutes that we watched them, there were 17 on the ground near the lights! Further along the trail, we came upon one female glowing in the grass. We were going to put her in a vial for the group to see up close, but then we noticed a male with her, so we left them alone. We found more than ten scorpions, a field cricket (this seems to be a good year for them in many places).

We started to move again around 9:20, checking a couple of holes that we’d found on the way in. As we approached one of them, I noticed a lump. A tarantula was sitting outside its burrow! That was a complete surprise, since it was so early in the year. The group walked by slowly, and the tarantula stayed put.

Tarantula out in June

Tarantula out in June

Other sightings for the evening:  Ash-throated Flycatcher, California Towhee, Spotted Towhee, and Wrentit; brush rabbit, millipede, 2 centipedes, 10+ scorpions, harvestman, wolf spider, oak moths, bumblebees at soaproot flowers; 3 bats; paintbrush, yerba buena, brodeia, Ithuriel’s spear, elegant clarkia, verbena, deerweed. We also saw glowworms on our scouting hike on 5/30.

More photos are here.


The glowworms that we see locally are mostly pink glowworm, Microphotus angustus. Females look like larvae, and don’t fly. They differ from larvae in having compound eyes and genital organs. Males fly, but only light under duress according to some sources. Females light up to attract the flying males.

Here is an animation of the glow-find system, showing how males find females.