Axion plagiatum - BugGuide.Net

Chilocorini, Axion plagiatum

This big "twice stabbed" looks a lot like C. stigma, but the size and dark abdominal segments are characteristic of Axion plagiatum (Oliver, 1808). Gordon(1) states that C. stigma tops out at 5.0mm, and C. cacti at 6.2mm. But both of those (and all Chilocorus) have all red/yellow abdominal segments. The MCZ has 2 former LeConte types which are now considered Axion plagiatum, which clearly show predominately dark abdominal segments. And he lists the size for Axion plagiatum as up to 7.0mm. The shape of the elytral spots is also stated to vary significantly, along with the body form. Gordon's key to the tribe determines Chilocorus with the first couplet, using "Postcoxal line on first abdominal sternum merging with posterior margin of sternum", with all other genera including Axion, "not merging". And from the descriptions of the genera, it appears Chilocorus has 8 segmented antenna (looking like 7), while Axion has 10 segmented antenna (looking like 9). In Axion there should also be a "narrow pale area at anterolateral angle of pronotum", which if I imagin hard enough, I believe I can see some suggestion of on the corners of your ventral image.

great post, and another new species for BugGuide :)

… Tim R. Moyer, 17 March, 2009 - 1:30pm

Woo-hoo!

I always wondered what this genus looked like:-) Thank you so much for the detailed discussion, Tim.

… Eric R. Eaton, 17 March, 2009 - 2:46pm

Than you, Tim

for the thorough dicussion. I will change the posted title to avoid confusions

… margarethe brummermann, 17 March, 2009 - 1:58pm

Thank you both for the kind words.

Although this certainly appears to be Axion and not Chilocorus, I should caution everyone that the abdominal coloration difference trait was my personal conclusion, and not what Gordon uses (strangely, he doesn't even remark that either species can be confused with the other, as he usually does in a case like this one). While I'm certain (using Gordon) of Chilocorus always having the red/yellow abdominals, he doesn't specifically mention Axion having dark abdominals. Yet the two Axion MCZ types clearly show this mostly dark coloration. I guess physical structures are more certain than fading colorations.

Now there's one other "Chilocorus" in BugGuide I need to correct (my own oversight) and join yours.

… Tim R. Moyer, 17 March, 2009 - 8:56pm