Thursday, November 06, 2008
I was checking in on the state of the crucifer-sucking harlequin bugs (murgantia histrionica) among the rank growth of lobularia maritima in the parkway, expecting to find a thriving colony of them in all life stages like I did last November. Instead I found a huge bloom of a different bug, Bagrada hilaris. These new bugs are a recent import from Africa, according to info on Bugguide, where they are a mildly annoying pest on (surprise!) plants in the family Brassicaceae . . . cabbages, mustard, turnips, broccoli, sweet alyssum, etc. The first post of this species on Bugguide is dated 8/26/08 from a southern California contributor. They remind one of a remix of the harlequin colors, a bit smaller and pointier.
Something has given B. hilaris an advantage over M. histrionica in my alyssum patch. I found just one harlequin bug adult among a preponderance of bagradas in various growth stages and mating. I haven't found any bagrada eggs yet. The harlequins lay eggs in rows on the underside of leaves on taller plants near the alyssum; it's not certain whether the bagrada does that or deposits eggs in or on the soil. Hypothesis: There are few or no natural egg parasites for Bagrada hilaris, possibly because of their soil-laying behavior. I've seen parasitized Murgantia egg clusters in past seasons. Eggs of bagrada more successful=domination of available habitat. This is a common pattern with imported pest species.
Or, does the success of the new bugs have a taxonomic root cause: 'Tis better to draw on a sense of humor (hilaris) than to become overwrought and stressed (histrionica) as one wends their way through the alyssum of life.