Pterostichus at Portola

Pterostichus lama. Image by Ainsley Seago

I recently was out sampling at Portola Redwoods State Park and my old friend Pterostichus lama was the main target of interest. Pterostichus lama is the largest New World pterostichine and in North America, the only comparably large carabids are species of Pasimachus. Although large and totally flightless, P. lama is distributed from SoCal to Canada and from the Pacific coast east at least to Nevada. Preliminary work on this species we did as part of a larger work on the subgenus Hypherpes (Will & Gill 2008) suggested that there may be a differentiated population in the coast range distributed  from Big Creek, north to at least Jacks Peak County Park. More “typical” specimens are found from Marin Co. northward. This makes the samples from the Portola area very interesting in terms of  determining if there is a cline, a mix or “hybrid zone”  represented by the individuals we see in this part of the state.

Some students and I went to the park to look for these big beasties back in April 2012, but we didn’t find any. This time I found a half dozen, some teneral and most importantly, several Pterostichus larvae. Probably these are 2nd instar P. lama larvae. The larva of this species is only known from the 3rd instar, so it will take a bit more work to confirm the identity of larvae, but the interesting thing is that all of them were found inside of Douglas Fir logs together with the termite Zootermopsis angusticollis. I’m slowly, but surely piecing together the life history of P. lama. It’s large, relatively common, but we actually know very little about it…like so many insects.

Roberta Brett helps me collect larvae from the rotten logs

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About Kip Will

I'm an insect systematist with expertise in carabid beetles, who is always happiest in the bush.
This entry was posted in Carabids, Entomology, Pterostichines and tagged , . Bookmark the permalink.

3 Responses to Pterostichus at Portola

  1. annabellezza says:

    Hi! I am always impressed by scientists and it’s such a breath of fresh air to be reading about “pterostichus lama” and “carabid beetles” of which I know nothing about. I can see how you can be happiest in the woods. Thanks for sharing.

  2. peejay says:

    I’ve heard Pterostichus lama described as ‘very large’, but, from what I’ve heard, it is about 26mm long. That’s large for Pterostichus, but ‘small to average’ for most species of Carabus (old terminology) in Europe. Procrustes coriaceus reaches 40 mm, and Procerus gigas reaches 60 mm, while most species are over 25 mm.

    • Kip Will says:

      North America has a very deficient Carabus fauna, only about a dozen species. A large P. lama, the big ones are in the Sierras, is the largest carabid in NA, comparable to Pasimachus. Those Procrustes are beastly big, but the largest carabid in the World is Catadromus, a pterostichine that tops out at 70mm and it flies! You have to go to Australia to see them.

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