Monday, October 14, 2013

Cannibalistic lady beetles

Just about everyone knows lady beetles; they're one of our most charismatic coleopterans. Far fewer people would probably recognize this beast, which resembles a six-legged alligator. It is the larva of the (now) most widespread lady beetle in these parts, the Multicolored Asian Lady Beetle, Harmonia axyridis. Heckuva long name for a 6 mm beetle. We'll just acronym it down to "MALB".

Ill-fated numerous introductions by people and organizations keen on aphid and other "pest" control brought this thing to us. Now, MALB's are ubiquitous and overly abundant. This is the lady beetle that swarms houses in late fall and piles into attics, crevices and other protected niches, much to the consternation of the homeowner.

I was in Adams County yesterday, and made the four mile round trip to the iconic Buzzard's Roost Rock, which is in the heart of the Edge of Appalachia Preserve. Even though this is, by Ohio standards, a largely wild and invasive-free landscape, it was shocking how many of these lady beetle larvae were there. A scan of small trees and shrubs would often yield a dozen or more lady beetle larvae.

Like the adult lady beetles, larvae are voracious predators. They'll eat aphids, but also apparently just about anything else small enough to overpower. Supposedly they are avid consumers of moth and butterfly eggs, and that certainly can't be a good thing for our Lepidoptera.

Brutish and thuglike, the MALB larvae are evidently not above cannibalism. Here, a pair of larvae bookend and consume another larva. I saw at least two instances of this yesterday, and I'm pretty sure this photo shows an actual live larva being killed and eaten - not the cast-off shed of a larva. MALB larvae go through five instar stages, molting into a larger iteration with each stage.

This is the pupal stage, which is usually affixed to a leaf.

The ultimate phase of the MALB life cycle is this, the adult lady beetle that many a homeowner knows and despises. That's too bad, as there are numerous native lady beetles, and they are charismatic and beneficial insects. Many if not most of them have suffered due to competition with the Multicolored Asian Lady Beetle.

One would hope that humans would learn the folly of introducing nonnative animals, but I have no great hopes that we will ever learn our lesson and quit tampering with "biological control".

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4 comments:

Ron Gamble said...

"Harmonia", eh? At first glance, that sounds like it should be a "good" thing... :-( . Thanks for the info on these mini-monsters; very interesting.

Ian Adams said...

Jim:

Cannibalistic (not cannabalistic)

Ian Adams

Jim McCormac said...

Thanks for the spell check, Ian.

Junior Barnes said...

Is it just me or are most of the invasive species in this country from Asia?