ID please plus behaviour? (1 Viewer)

The pictures included I took in early May, 2009 on a high hilltop in the Alentejo, Portugal. These beetles (?) were settling on the base of a fire watch tower and on rocks nearby (with a few other species - inc. earwig sp). I've seen this phenomenon at the same place a number of times - always in hot (c.28-30ºC) weather. The site is good for seeing butterflies hill-topping (mainly Southern Scarce Swallowtail, Common Swallowtail, Southern Gatekeeper and Cleopatra) but not in large numbers. The insects in the photos were present in extremely large numbers - probably over 50,000 - the photos don't do justice. Is this common behaviour?

There are some large communication masts on the same hill but they are inaccessible and too far away to see if these pretty things were also congregating there. (No I'm not suggesting that these insects were affected )

The beetles are Chrysolina americana (rosemary beetle), a flightless species native to Europe (despite the name). I've never seen concentrations like those, very impressive and interesting. Perhaps they're breeding swarms.

I wonder what the Earwigs are up to then?

andyadcock said:

I wonder what the Earwigs are up to then?

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There could have been something there (over the cement/metal structure) that our limited human senses cannot detect (especially from photos!) and that could have eventually been attractive for the earwigs as it was for the beetles. Just an idea, but no idea really :king: o

RafaelMatias said:

The beetles are Chrysolina americana (rosemary beetle), a flightless species native to Europe (despite the name). I've never seen concentrations like those, very impressive and interesting. Perhaps they're breeding swarms.

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Many thanks Rafael! The hill in question, I'm sure you will know is Serra de Alcaria Ruiva (370m). I'm guessing (if my memory isn't failing) I have seen these beetles in some numbers, albeit much smaller amounts than on the day (5th May, 2009) I took the photos, some half a dozen times. Sometimes in the order of 100 or so and others in low hundreds. The immediate area has some wild Rosemary and plenty of Lavender. I had assumed they had flown there so them being flightless is even more remarkable. I've looked them up and they are nocturnal I see and these were fairly static with some moving around to get into bits of shade. Some climbed up my tripod and trouser legs. I hope that this can be seen by somebody more knowledgeable again and solve the puzzle!

RafaelMatias said:

There could have been something there (over the cement/metal structure) that our limited human senses cannot detect (especially from photos!) and that could have eventually been attractive for the earwigs as it was for the beetles. Just an idea, but no idea really :king: o

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I wondered if they could have just walked up and up until they reached the top - why?

Simon Wates said:

Many thanks Rafael! The hill in question, I'm sure you will know is Serra de Alcaria Ruiva (370m).

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Sure do, beautiful place in spring and a top spot for large eagles and other raptors (I'd guess that most Iberian raptors have been seen there?).

RafaelMatias said:

Sure do, beautiful place in spring and a top spot for large eagles and other raptors (I'd guess that most Iberian raptors have been seen there?).

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Apart from rarities yes - though I have seen Rüppells there twice. On some visits, upwards of 10 species in a couple of hours inc. 5 eagle species.