Monday, 4 March 2013

Ants on Parsonsia.

Southern ant with its head in a Parsonsia flower; its hairy abdomen is at the top of the picture, head (also hairy) at the bottom.
A couple of climbing plants are having a second crack at flowering right now.  Muehlenbeckia australis and Parsonsia heterophylla are both flowering again, even though the same individuals flowered heavily back in November.
Parsonsia heterophylla, Karori November 2012.
Muehlenbeckia australis, Karori, November 2012.
The Parsonsia flowers were covered in little black ants, which I didn't see in the November flowering.

It's hard enough to identify plants from photos and we don't like being asked, so I'm grateful to Professor Phil Lester for telling me this is probably Monomorium antarcticum, the southern ant. It's a common native species, or more likely a species complex.  My pictures don't show the mandibles and the segments of the antennae, which are needed for a formal identification.

Head to head, two ants probe the same flower.
It's tempting to make the assumption that these are pollinators.  There were large numbers of them, they were concentrating their attention on the flowers, probing deep into the centres of them.  But it's harder to test the idea.  You'd need to show they were carrying pollen on their bodies and transferring it effectively between flowers.  Phil Lester says he's seen Monomorium visiting flowers before, and with pollen on the hairy parts of their bodies, so they might transfer pollen between flowers, but less likely between vines.  Heine (1937) recorded several flies, including both Tachinids and Syrphids, a beetle, and several moths, but not ants, as flower visitors to Parsonsia heterophylla.  It seems likely to me that if ants are pollinators of Parsonsia they play only a minor role compared to other insects, and if they're stealing nectar they might even be counter-productive overall.


Heine, E.M 1937.  Observations on the pollination of New Zealand flowering plants.  Transactions of the Royal Society of New Zealand 67: 133—148. 

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