Spotted at the Rockingham Environment Center, advertising their presumably unpleasant taste, probably derived from the highly aromatic plants they feed on. 

This Pentatomid is native to Australia, but is so overly attracted to the highly invasive and noxious (in both senses of the word) weed Horehound (Marrubium vulgare) that we don’t know what the original host plant was. Given that other known hosts for the bug include Lavender (Lavandula), as here, and Salvia (S. divinorum), it was probably something in the Lamiaceae. 

Horehound is native to many parts of Eurasia and north Africa, but is now found in most parts of the world. It was introduced to Australia as a medicinal plant, supposedly useful against respiratory complaints, but there’s no evidence that it’s actually useful for any such purpose. 

Unfortunately, despite the Horehound Bug’s enthusiastic appetite for Horehound, it doesn’t appear to be very useful as a biological control - and the reason appears to be another species actually introduced as a biocontrol agent, the egg parasitoid wasp Trissolcus basalis. This Platygastrid wasp was originally introduced to Australia in 1933, to control the Green Vegetable Bug Nezara viridula, another Pentatomid species. Not only is the wasp highly territorial, chasing off other parasitoids from whatever area she has claimed as her turf and reducing the number of Nezara eggs that actually get parasitised, it also targets the eggs of at least 25 other species of Pentatomid Bug, including Predatory Shield Bugs that would actually protect crops from other pests. So the wasp’s failures as a biocontrol include making the Horehound Bug fail as a biocontrol. 

Far from the best photo I've taken. I was paying more attention to the Horehound Bug on the plant. Here's a much better picture from Wikipedia.

Marrubii was the Latin name for the plant. The common name in English is derived from the Old English hoar (furry, as in "hoarfrost") and hune (a word of unknown origin designating a class of herbs or plants). "White" distinguishes it from Black Horehound, Ballota nigra, a similar-looking herb formerly in the same genus.

A grey-leaved perrenial herb from the mint family, growing up to 45cm tall, and native to Europe, Northern Africa, and southwestern and central Asia. Widely naturalized in many places, including most of North and South America, deliberately introduced to Australia for supposed medical use, and highly invasive in New Zealand where two species of moth are being trialed as biological controls.

Date: 9/11/2019

Time: 11:45 AM

Location: Lower Arroyo Park, heading towards the Arroyo Seco Trail

Route:  Heading towads the Arroyo Seco Trail from the parking lot, take the walkway to the east of the parking lot.  On that walk way, there will be a field with a Western sycamore on the north side, about 50 ft into that field, you’ll find about 3 marrubium vulgare, all within 5 ft of each other.

Weather: About 80F, warm and sunny.  I found the white horehound under the shade of a sycamore tree, so it was a little bit cooler.

Habitat:  sycamore forest.  There were a lot of sappy/sweet berry trees around, which meant a lot of ants surrounding the area.  The soil was covered by fallen Western sycamore leaves.About 10 ant piles visible within the 8 ft radius of the horehound.

MARRUBIAM VULGARE - WHITE HOREHOUND

Even though its an invasive, marrubium vulgare is one of the coolest plants I’ve seen.  I really quickly fell in love with its fuzzy textured leaves.  When I first saw them, I tried to sketch their pattern, but my drawing skills were limited.  I saw three white horehounds within 5 ft of each other.  Out of all 3, this one was the tallest, coming in at maybe 10 inches tall.  The leaves on this plant were round, with white hairs, and super textured. They curled inwards, but not tightly.  

The stems of this plant were also fuzzy.  I noticed that at the point where the stem branches off to a leaf, there was some flowering - cream/beige tiny flowers grew in that little crevice.  Most of them had either dried up or fallen off.  The leaves on this tree grew in a pattern that was spiraling upwards.

Botanical Name: Symphytum officinale Common Name: Comfrey Folk Names: Assear, Black wort, Boneset, Bruise wort, Green plant, Healing herb, Kara kaffes, Wall wort, Miracle herb Habitat & Description: Zone 4-9, Stout bristly-hair perennial with mucilaginous…