The world of insects is ancient, impossibly diverse and critical to the underlying workings of nature. Yet in some ways, insects seem so utterly alien that they often serve as models for science fiction creatures invading from other galaxies.
Insects preceded the move by four-footed creatures out of ancient seas and onto land by hundreds of millions of years. Over time, they’ve co-evolved with plants and animals into every possible niche of earthly landscape and complex, intertwined relationships. Despite their infinite diversity, insects’ lifecycle is almost universal: a flying, six-legged adult mates and lays eggs that hatch as larvae, feed voraciously until mature, form some type of cocoon in which they transform and then emerge in adult form, ready to mate again. Some insects spend most of their lives in the larval stage, while others have longer adult phases. I thought it would be fun to walk through a few of the more unusual insects of West Marin and beyond.
The prionus root borer
This unusual beetle gave me the original idea for this essay. Late last November, on a tracking walk, our club found several coyote scats on the side of the Kehoe Beach Trail that were full of unusual, bright, red-brown insect remnants—carapaces, legs and antennae—along with the usual rodent fur. The distinctive red-brown is the color of a large adult beetle, about two-and-a-half inches long. The larva is even bigger, up to four inches long, and is a common agricultural pest in California living for up to four years in the root systems of fruit trees (the adult beetle lives only a month or two). None of the experienced naturalists in our group had ever seen this bug in West Marin. I’m not sure which plants they were eating out there in the grazing fields and chaparral, but I surmise they had a later-than-normal adult hatch that was washed out by the unprecedented early and extremely heavy first rainstorms of the season. Coyote, in his magical way, took instant advantage of the rare opportunity.
The bot fly
This one is kind of creepy, in that otherworldly way of insects. It is also quite beautiful. The bot fly is big and fat—about a half-inch wide and an inch long—as is its larvae. I found a big grey larva working its way across a gravely trail one day. It was extremely primitive in its six or eight segments, short and stubby, no legs, no obvious eyes, slowly hunching along. The adult lays its eggs on host animals, including humans; upon hatching, the larva burrows under the host’s skin, where they grow quite large, appearing as bumps until they mature and burst out of the skin. Then they drop to the ground, make cocoons in the soil and eventually emerge as flying adults. A week after I found that larva, I found an adult clinging to a vertical grass stem along the shore of Abbotts Lagoon, fuzzy, brown and rather attractive. These were the only times I’ve ever seen this bug.
Indian toe biter
Another unusual and uncommon insect, this water-dwelling beetle hunts small fish in ponds and slow streams. I found one washed out of Kehoe Creek. The toe biter is flat, mud-colored and large—about two inches long. The leg sockets and body joint sockets are obviously designed for underwater life. Its underside reminds me of Jules Verne’s Nautilus submarine. It eats the small fish it catches by inserting its proboscis into the fish’s eyeball. Apparently, it will also try to do that to the toe of a barefooted human.
California praying mantis
I love these large insects, which I mostly see in the tall early-summer grasses of Bear Valley meadows. I’ve seen them up to four inches long. Their shield-shaped, swiveling heads turn in the direction they are looking and give them a hint of humanness, perhaps abetted by their folded up, “praying” hands. In fact, they hunt with those front legs, with a lightning-fast grab reaction when an unsuspecting insect comes too close while they masquerade as a plant stem. Praying mantises come in greens, yellows and browns that blend well in the foliage. They are extremely predatory and carnivorous and will even take small birds. With people, they are very docile and don’t seem to mind a bit of handling.
Jerusalem cricket (potato bug)
This bug holds a personal connection because I only recently overcame my fear of it and learned it is quite easy to pick up and handle. I believe part of a tracker’s task is to overcome fears in nature through observation and knowledge, and this was a great breakthrough for me. I always found potato bugs kind of scary, with their strange fleshy color, skull-like shiny head, tan-and-brown striped abdomen, and large and fearsome-looking mandibles. They can reach up to two and a half inches long. They are not a true cricket, and they did not originate in Jerusalem. Though they might bite if agitated, they are not poisonous.
Mormon cricket
Though this amazing cricket is not a West Marin bug, I had a recent experience with it. This desert insect will occasionally explode into populations of billions. I was car camping on remote dirt roads across Nevada last spring when there was just such a statewide event. Other than on the high ridgetops where I would camp, the whole state was overrun with a solid carpet of the insects, migrating across the landscape in endless armies. The paved roads became oily-slick and dangerous, with millions of their crushed bodies. Pretty creepy!
Darkling beetle
The beetle realm is extensive and diverse, but my favorite beetle is quite normal and common: the large darkling beetle. One of the head-standing beetles, it is not a stinkbug but it is one of many beetles that mimic it. This local beetle runs up to an inch and a half long and moves slowly, as is normal for a plant-debris scavenger (as opposed to fast predatory beetles). I find them handsome and appealing, with their smooth, shiny black carapace and head. They are quite friendly to pick up and examine, and they are one of the best beetles from which to learn about the classic “alternating tripod” walking style, an amazingly efficient way to keep all six legs well-organized. Next time you see one on a trail, take a slow-motion video and watch its precise movement at an easier-to-see speed. The redwood moth
I cast a hopeful vote for this large and beautiful moth, which I grew up seeing frequently, especially in summer, but haven’t seen for over 20 years. Reddish brown in color and over four inches wide, with bright eye spots on its wings, the redwood moth is attracted to lights at night. The ceanothus silk moth is similar and more common.
A few more deserve at least a quick mention. The sand wasp is a common, solitary, predatory wasp that digs tunnels six to eight inches deep into firm sand. There it deposits an egg into a small cocoon composed of sand and bee-spit. It is non-aggressive and a remarkably efficient digger.
The ant-headed beetle is a one-inch beetle with a long, dragging abdomen and a square, very ant-like head. It hunts and digs up the sand wasp larvae, leaving winding trails hundreds of feet long across the sand.
The California tarantula is hairy and brown, growing up to nearly three inches long. It is not poisonous or venomous and is actually quite friendly, though it can cause a rash with its hairs. This tarantula can live up to 35 years. Scorpions and black widow spiders are indeed venomous but are they rare and reclusive in our area.
Large grasshoppers deserve a mention as an important a food source for so many local animals, from hawks to coyotes, weasels, skunks, raccoons, opossums, snakes and lizards. I’ve seen coyote scats composed entirely of grasshopper remains. When they are hatching out in the dry fields, they can be prolific. Millipedes are surprisingly widespread in sandy areas, leaving distinctive, stiff, double-track trails. Millipedes have a long, tubular shape; centipedes are the flatter, much wigglier creatures most often found under logs or planks, where they forage organic debris. Wolf spiders are a fast, predatory spider that lives in small cylindrical web-nests in forest floor debris. Hiding in its little den, it rests its two front feet on the ground in front, sensing the vibrations of the footsteps of passing insects, then rushes out to bite and subdue them. Seaweed flies are a tiny, ubiquitous fly on our beaches, laying thousands of eggs in the decaying kelp it feeds on. Its real significance is how heavily the coastal plovers feed on it and its larvae, leaving probing marks up and down lengths of kelp.