Thursday, 15 January 2015

More on the swarm?

The swarm referred to is that covered in this post from Tuesday.  I mentioned in that post comments by Frances about some nearby willows having many little black insects on them.  Today she showed me where they were and I have perpetrated photography on them.

This first shot is one of several small clusters of insects on the willow.  My guess is that the insects are about 5mm long on average.
This shows them a bit better (click to enlarge the image).  It may be significant that one of them, in the upper left of this image, clearly has wings.
Finally I caught this one doing a runner.  There seemed to be others moving about with wings but they escaped my attentions. 
A colleague has nailed the ID:
He has subsequently advised that "..they don’t form swarms as far as I know, although they do have a winged form for dispersal."  That makes two knowledgeable votes against the swarms being this species. 

Interestingly there are no records of this species in the Atlas of Living Australia.  So I have offered my photos for a record.

Another colleague has commented that it would be very difficult for the aphids to have traveled on the wind as suggested in the linked article.  He went on (paraphrased by me) to note  that people  assume that an insect that has appeared in Australia from a NZ source has migrated on the wing.  This would be very unusual but apparently the aphids were first found in Tasmania after a period of strong Easterly winds so in this case it might be possible.  More generally there are many ways that aphids move around and includes on clothing, plants, freight and almost anything. They are parthenogenetic that helps. 


The aphids are still on the willows a month later.  They are in such numbers that the honeydew they deposit is dripping off on to the drive so as to make it seem wet and the metal picks up on our tyres.

3 comments:

Ian Fraser said...

Hi Martin. I'll wait for Steve's or others' more informed opinion but my gut feeling (without having seen them first hand) is that I'd not expect these characters to form the sort of flying swarms you photographed, but then again I'm a mine of ignorance on inverts. I'm intrigued by the use of 'orange gooeyness when squashed' as a taxonomic character, but I'm always open to new information! I can't see mouthparts, so can't say for sure if they're hemipterans as you suggest, but wouldn't be at all surprised. Not sure if this helps at all.

Flabmeister said...

Thanks Ian. I'm always excited when I find I have contributed an innovation to scientific thinking. I would be even more excited if it wasn't for the fact that, so far, the new thoughts tend to resolve to being hallucinations rather than visions.

Martni

Flabmeister said...

I am perhaps less nuts than I feared. Cochineal comes from a member of Hemiptera, not as I feared possible coleoptera. That is what made me think of the colour!