Monday, February 10, 2014

convergent lady beetle ~ 02/10/14 ~ Stevens Creek


Holy cow!  Wow!  Just... wow.  When I first heard about this phenomena happening in the Sierra Nevada during my first entomology class 20 years ago, I mentally placed it on my bucket list of things I wanted to witness firsthand.  In my mind's eye, I had pictured maybe a gallon's worth of beetles at the base of a large tree.  Actually seeing this exceeded all my long-held expectations... by a long shot.  Wow.

During my museum stint in Cleveland, I fielded calls about aggregating ladybugs around Halloween, but instead of doing their thing out on the forest floor like shown above, the introduced multicolored Asian lady beetles (Harmonia axyridis) preferred the warmth in or on human structures.  I don't blame them, it's gets awfully cold in Ohio. Imagine having a horde of ladybugs on the wall of your living room?  Interesting, but not pleasant to live with.  They make such a mess and are not good house guests.  My advice to folks who called was to use a vacuum cleaner, as this Ohio State Extension Fact Sheet clearly explains.

There are lots of different kinds of lady beetles and many of them look very similar. According to Powell and Hogue, there are more than 125 spp. in CA alone.  I couldn't find any information on whether all lady beetles gather in some capacity for the winter or not, or even if they move their gathering spot around.  I believe the recent, decent rains helped create this massive and extensive aggregation.  By the next day, Randy @ Way Points discovered there were much fewer here, but his pictures are still impressive. I've heard the term hibernate thrown around when referencing lady beetles, but I don't think that's an accurate use of the word.  Does anyone have a better descriptor for what lady beetles do in the winter?  Diapause?

Sigh... now, this was one of several of our day's findings which prompted some discussion about, as Cindy put it, the "delicate process of protecting natural resources on public land."  I have to admit, that's one thing I do not miss about being affiliated with an institution, organization, or governmental body - that kind of public tiptoeing over my own sheer joy of nature.  For my own blog, I've laid out some basic, good-sense ground rules and generally don't worry about what other people will do with the limited information I choose to share.  However, this time I'm trying to be especially respectful of other people's concerns.  So, in the interest of sharing the wonder of nature, I've been given the green light to post about this very cool lady beetle phenomena... despite the fact there are people who could profit from such a find.  Indeed, most of those garden centers that sell ladybugs?  Well, where do you think they get them?  Eh-hem.  My advice?  As a rule of thumb, do not purchase lady beetles, even if it superficially appears to be the "green" thing to do for your garden.

ps 08/22/14 - Cat Ferguson from the Awl asked for permission to use my photos to illustrate ladybugs harvested in the Sierra Nevada.  I initially declined, "Thank you for your permissions request and compliments on my photos.  Unfortunately, I am denying your use of my photos to illustrate Sierra Nevada lady beetle congregations, because my photos were taken in the Santa Cruz Mountains - totally different habitat with different trees.  To the trained eye, it is not factually correct.  Isn't the Awl motto Be Less Stupid?  And, for the record, I am against wild-collecting ladybugs for sale as natural pest control.  Due to their documented seasonal pattern of winter congregation and then obligate flight dispersal before chowing down on aphids, they are not effective as directed pest control.  All collecting achieves is quick money for the sellers and a disruption of natural processes, which could potentially have a negative impact on our native beetle populations."  After assuring me her article would be about general Northern CA ladybug populations, not just Sierra Nevada, and about the ineffectiveness and problems with wild collection, I finally agreed for a fee.  Eh, my photos ended up not being used, and that's fine by me.  Cat's "The Flight of the Ladybugs" contains an interesting tidbit  from a 1919 California State Commission of Horticulture bulletin about dispersal of the ladybugs.  We've known for almost a hundred years that releasing ladybugs at a location doesn't work, and yet it remains a commercial enterprise?  Too bad.  I've got a bridge to sell you.

7 comments:

Jennifer said...

Holy Cow was my thought exactly! Amazing!!!

I saw this same phenomena on the Palo Corona trail a few years ago and it was a sight to behold.

I guess you could say I'm guilty as charged as I do sometimes buy them at Orchard.

randomtruth said...

I think diapause is the correct term, Katie. It's my understanding that the convergent lady beetles do this every year to overwinter and conserve energy while their food - aphids - isn't available. Much like many insect blooms, including aphids, the rain and warmth of spring triggers their emergence.

And I agree - this colony especially is quite a natural wonder. Not unlike the Monarch congregation spots. It was fun running into it with you.

GretchenJoanna said...

That is astounding!
And I didn't know about the problems with commonly available ladybugs - thank you for the heads-up.

John @ Sinbad and I on the Loose said...

This most indeed would be an unforgettable sight to behold. Lucky you.

Katie (Nature ID) said...

Ya, Ken, I was surprised 2 of my UC Press books say "hibernate", written by university professors. We were incredibly lucky this day. It was so good to meet you. I hope we get together again.

Gretchen and Jennifer, honestly, I hadn't given the ladybug purchase much thought before, since I've never done it. I just know it's common knowledge among entomologists that releasing lady beetles in your garden doesn't work for aphid control, because of their documented need for flight before settling in anywhere. Seeing this spectacle really hit home for me what's actually involved.

John, I sent you an e-mail.

Imperfect and Tense said...

Oh my giddy aunt! That is truly amazing! I've seen the occasional couple of dozen Harlequin Ladybirds roosted in the roof space of the old Tense Towers, but nothing on such a grand scale or out of doors. I bet you're still grinning at the sweet memory!

Katie (Nature ID) said...

Graeme, I love your expression OMGA. I believe the harlequin lady beetles and multicolored Asian lady beetles are different names for the same species, introduced here and across the pond: http://www.earthgate.ucsb.edu/mobile/events/department-news/1321/asian-ladybugs-invade-east-coast-homes/.