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Archive for August, 2013

New publications

We have a few publications accepted in the last few months. Two of which that are currently available are about the crepuscular-nocturnal bull ant, Myrmecia pyriformis.

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The crepuscular-nocturnal bull ant, Myrmecia pyriformis, about to leave its nest during the evening twilight.

In one story (1), with Sam, Bob and Jochen, we documented the nocturnal foraging style of these Myrmecia ants. It turns out that majority of ants from each nest carry out just one trip per day (technically night), starting close to sunset and ending around sunrise time. The few (<10% of the forager force) who make multiple trips are the ones that return with prey. The others seem to return with some form of food (most likely honeydew, sap). We determined this by weighing individual ants before  and after foraging. We found an increase in body weight of individuals returning without prey – about 13mg on an average for an ant weighing 95mg, which is quite substantial. Those individuals that carry out only one trip seem to be the non-hunting ants.

Foraging behaviour of 177 individually marked ants. From Reid et al., 2013 Aus J Zool.

Foraging behaviour of 177 individually marked ants. From Reid et al., 2013 Aus J Zool.

So, this provided a natural spread of the times at which animals return home: those with prey return at night, some return during sunrise, thus experiencing a wide range of light intensities under which they need to navigate.

In the second study (2), with Chloé and Sam, we addressed how the navigational efficiency of these ants change at different light intensities. As it gets darker, ants stop longer and more frequently while foraging. This allows them to capture more light to create a brighter but coarser view of the world, which gives them enough information to head in the right direction for a short distance. At low light conditions they have huge problems in navigating to the nest and especially in pinpointing the inconspicuous nest entrance. Often, ants walk right on top of their nest entrance and continue to spend several more minutes searching for the nest entrance. At bright light intensities they walk faster and are most accurate in locating the nest. So despite being strictly crepuscular-nocturnal their navigational efficiency suffers at low light conditions. This indicates that (a) nocturnal bull ants are visually guided even at low light conditions, (b) most foragers avoid navigating at night because they are really bad at it and hence restrict their navigational tasks during dim lit periods of twilight.

As light levels drop, pause duration increases and walking speed decreases of ants decreases. Colours indicate data from two nests. Narendra et al., 2013 PLoS One.

As light levels drop, ants pause for longer and walk slower. Colours indicate data from two nests. Narendra et al., 2013 PLoS One.

1. Reid SF, Narendra A, Taylor RW & Zeil J. 2013. Foraging ecology of the night-active bull ant, Myrmecia pyriformisAustralian Journal of Zoology 61: 170-177.

2. Narendra A, Reid SF & Raderschall CA. 2013. Navigational efficiency of nocturnal Myrmecia ants suffers at low light levels. PLoS ONE 8(3): e58801.

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New Pics

It has been a really busy winter in the southern hemisphere. Was at the Bäckaskog Castle in Sweden, attending the Invertebrate Vision Conference followed by the Symposium on Vision in Dim Light. Since being back, getting ready for a fieldtrip to Poochera to study the charismatic Nothomyrmecia. Over the last week or so, I started updating the ant gallery. If you have not been there for a while, now is the time!

Some important additions: Anonychomyrma (Perth), Calyptomyrmex (Borneo), Colobostruma (Murramarang National Park, NSW), Meranoplus (from Australia and India), Opisthopsis (three species from Australia) and Harpegnathos (from India via Paris!). Below are a few pictures.

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Calyptomyrmex lowreyi, Sabah, Borneo. Ants of this rare genus, Calyptomyrmex, are known from Africa to India east to New Caledonia. They are known by 28 species. In a recent revision (2011), Steve Shattuck indicates that these ants are so rare that they have been collected fewer than 20 occasions! Very little is known about their biology, other than that they are ground foragers that nest within rotten word and in soil. The enlarged hairs on their body, seen in several Dacetine ants, is thought to assist in retention of soil acting as some sort of a camouflage.

Colobostruma alinodis

Colobostruma alinodis, Murramarang National Park, NSW. Locally abundant, these ants have an unusual 4-segmented antennae.

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Colobostruma alinodis, Murramarang National Park, NSW. Nests were in the soil underneath wet leaflitter in a wet sclerophyll forest.

@ Mt Ainslie

Camponotus consobrinus males, Canberra, ACT.

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Melophorus hirsutus, Canberra, ACT.

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Anonychomyrma itinerans perthensis, Kalamunda National Park, Perth

Camponotus molossus, Perth

Camponotus molossus, Perth. These ants make elaborate chimney like nest entrances.

Harpegnathos saltator, Shimoga, India

Harpegnathos saltator, Shimoga, India. The renowned jumping ant, from a colony in the lab of Christian Peeters, Paris.

Opisthopsis pictus, Pallarenda, Townsville, QLD

Opisthopsis pictus, Townsville, QLD.

Meranoplus bicolor, Bangalore, India

Meranoplus bicolor, Bangalore, India

 

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