Saturday, December 8, 2012

An Omus Hot Spot

          There are numerous countries I dream of visiting to witness the fauna of, most notably countries of Africa. One attraction is that Manticora and Mantica Tiger beetles occur there, representing the last tribe of Tiger beetles I'm missing from my collection (after Cicindelini, Magacephalini, Amblycheilini and Collyridini.) -wait a minute, though. Something is missing here. I live in one of the 3 states and single provenance that has a Tiger genus all to itself; Omus. Also, North America is the only continent containing the tribe Amblycheilini with the genera Omus and Amblycheila. In reminding myself of this, I don't feel as unsatisfied.


Omus californicus
intermedius Leng.

Look at the beast! If I lived in another country, I'm sure I'd be dying to visit the Pacific Northwest.

I've encountered this species on several occasions during my times in California, not this year, however. Next spring I plan on setting up a pitfall trap at a hidden hilltop in the Sierra National Forest where I found a condensed population of about dozen specimens, (excluding specimens I didn't find in those few minutes.) The reason for a single trap is to simply not have another occasion where I collect dozens of unneeded specimens, when this native and unique species could be repopulating at this spot at a  healthy rate.

Another gem at this spot happens to be another ground dweller, Metrius contractus (Family: Carabidae, Subfamily: Paussinae). This is another species I'm desperate to collect a few more of. I only found one specimen on that day, and it some how lost it's right antenna. I recently cleaned this specimen up (as not seen in this photo, (apologies for the laziness)) and relaxed it with boiling water, then braced the left antenna close to it's body to prevent some of the risk of it's disappearance in it's years to come. I also went through the collection and relabeled this, and many other specimens with larger labels from my earliest collecting, saving space in the collection and thereby money.


Metrius contractus
Eschscoltz

The bombardier beetle Metrius contractus discharges its defensive secretion
 as a froth that clings to its body. When attacked from the rear, it allows the
 froth to build up over the gland openings near the abdominal tip; when attacked
 from the front, it conveys the secretion forwards along special elytral tracks.
 M. contractus has two-chambered defensive glands typical of bombardier beetles, 
and its secretion, like that of other bombardiers, is quinonoid and hot. Its frothing 
mechanism, however, is unique for bombardiers and possibly illustrative of the 
ancestral glandular discharge mechanism of these beetles. M. contractus, thus, 
could be the least derived of extant bombardiers. (1)

...just another example of how awesome Ground beetles are. Omus also has it's own secretion, a black liquid released from it's mouth organs, streaming onto it's mandibles when attempting to bite some unlucky creature, including myself on a particular occasion.
 

Sierra National Forest:
Habitat for Omus californicus
and Metrius contractus

I have three of the six or seven Omus species in my collection: O. californicus, O. audouini and O. dejeanii. The next species I have targeted is Omus submetallicus, the most geographically restricted of the species only being found on the north-facing slopes of Warthan Canyon in Fresno and Monterey Counties, California. I shall post updates on the two different Omus collecting plans next spring.

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