Wild Neighbors: Beetle Convergences and Termite Emergences

By Joe Eaton
Wednesday December 10, 2008 - 06:09:00 PM

The early November rains made me briefly hopeful, although that didn’t last long. They also seem to have faked out some of our local insects whose life cycles are keyed to changes in the weather. 

A few weeks ago I heard from one of the Save Strawberry Canyon folks that lady beetles (a more satisfactory name than ladybugs, or ladybirds) were swarming at the lower end of the canyon’s fire road, clustered on the dry stems of poison hemlock. She was surprised to see such an aggregation, but was told by a neighbor that this was an annual event. I was a little surprised too, having always considered this a Sierra phenomenon. 

But it turns out that lady beetle conventions of this kind are well-documented in the Coast Ranges as well. The species involved is the convergent lady beetle (Hippodamia convergens), so maybe we should call them convergences. How harmonic they are I couldn’t say. The beetles don’t seem to interact much; they all just show up simultaneously at the same spot.  

Sue Hubbell, in one of her wonderful insect essays collected in Broadsides from the Other Orders, says these gatherings are triggered by autumn rains. The lady beetles stay dormant through the cold wet months, rousing themselves and heading out for an aphid snack in February or March. I hope the false start of the rainy season hasn’t deranged their schedule too much. 

I’m less concerned about the fate of the termites that struck out to found new colonies after the recent rains. Those would be the western subterranean termite (Reticulotermes hesperus), the most destructive termite species in California according to the authoritative California Insects by emeritus UC professor Jerry Powell and the late Charles Hogue. In addition to the understructure of houses, R. hesperus damages fruit trees, grapevines, and the occasional potato. 

It appears that the first serious work on colony foundation in this species was done by Frances Weesner. At a time when female entomologists were uncommon, Weesner was associated with the UC entomology department in the 1940s and ‘50s. I don’t know whether she was a faculty member. She corresponded with a large network of pest control professionals, who would send her interesting things they had killed. 

Weesner kept careful track of emergences by the winged adult termites, or alates, around the Life Sciences Building for several consecutive years. Timing varied; most events were in October or November, with an outlying date of Aug. 29, 1951. The alates tended to take flight on the first clear day after a rainstorm, with colonies in warmer soil going first. Termite nests under buildings and pavement staged later emergences than those in an open courtyard. 

She reported that the winged termites often found a reception committee of hungry ants: “The ants are very active during emergence of the alates in the early fall and rapidly congregate around exit holes where they take a high toll of the alates.” If the ants got greedy and entered the diggings, the termite workers would seal the exit. 

Alates that successfully ran the ant gauntlet shed their wings and formed tandem pairs. Weesner didn’t say—and may not have known—whether mates from foreign colonies were favored. 

If a female lost her partner, she would assume an invitational posture and wait for another male. The pair, the incipient king and queen of a new dynasty, would wander around until they found a ready-made hole in the ground, which they then set out to enlarge. They never dug from the surface. 

Picking off her own supply of emergents, Weesner established colonies in her lab and monitored their progress. Her founding pairs waited from 13 to 36 hours before mating. Since females can store sperm for up to six months, she’d be all set for a while. A typical queen began her egg-laying career about a month after leaving her natal colony.  

Once workers began hatching, the colony was up and running. The soldier caste was slower to appear; in fact, only 18 of Weesner’s 2040 experimental colonies ever produced soldiers in the first six months of observation. 

I couldn’t find much more about western subterranean termites specifically. The genus Reticulotermes varies in social structure, from simple families with a monogamous founding pair to interconnected nests with inbreeding workers. (Unlike ants and bees, worker termites are not necessarily sterile.) Some species go through as many as eleven developmental stages and show a complex division of labor.  

Termites, unfortunately, have never found their E. O. Wilson or Karl Von Frisch. (There’s very little about them in the magisterial new volume by Wilson and Bert Holldobler, The Superorganism.) 

For a bunch of social cockroaches, they’ve done quite well for themselves, often at our expense. Formosan subterranean termites, for instance, have been blamed for weakening the New Orleans levees that gave way when Katrina struck.