Ant Behavior

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When the weather is cold and cloudy, many people dream of sunbathing on a warm, tropical beach. What about ants? Evidence suggests that at least some ants spend time basking in the sun.

See, for example, this video of harvester ants (Pogonomyrmex) sitting in the sun after a rain.

News From Rockcliff Farms blog has photographs of imported fire ants (Solenopsis invicta) sunbathing in large groups during a midwinter warm spell.

Some possible reasons for sunbathing/basking:

  1. Warm up or increase body temperature, particularly in poikilotherms (animals whose internal body temperature varies with the external environmental temperature)
  2. Exposure to ultraviolet light can kill microorganisms, such as bacteria, on the outer surface
  3. Exposure to ultraviolet light in vertebrates induces the production of Vitamin D

 

In his 1995 book Animal Architecture, Juhani Pallasmaa stated wood ants (Formica sp.) use heat captured by basking in the sun to warm their nests.

Kadochová, Frouz, and Roces (2017) recently tested this idea in the laboratory. They found Formica polyctena workers are willing to bask under an artificial heat source, which in this case was an infrared lamp. The authors of the paper didn't find evidence basking workers had a sustained increase in metabolic rate, but did suggest that heat energy absorbed during sun basking can be dissipated enough to increase the temperature inside of the nest. Cool! (yeah, I couldn't resist.)

The authors of the study found certain behavioral castes bask more than others. It would be worth investigating if workers which spend more time with the brood are more likely to bask. The ability to increase the nest temperatures around the brood during cold spells would likely be an advantage.

What do you think?

References:

Kadochová Š, Frouz J, Roces F (2017) Sun Basking in Red Wood Ants Formica polyctena (Hymenoptera, Formicidae): Individual Behaviour and Temperature-Dependent Respiration Rates. PLoS ONE 12(1): e0170570. doi:10.1371/journal.pone.0170570

 

(Amazon Affiliate Link)

Pallasmaa, J. 1995. Animal architecture. Helsinki: Museum of Finnish Architecture. 126 p.

Looking for ants? Sometimes it is only a matter of finding the right plant.

Most people know ants come to the extrafloral nectaries on peony buds and we've talked about sandmat before, but are there any other plants that regularly attract ants?

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The umbel flowers of wild parsnip (Pastinaca sativa) might be a good place to look for different kinds of ants.

wild parsnip leaf

Wild parsnip grows in wet areas, such as along creeks or streams.  It can also be found growing on roadsides. At four to five feet tall, the flowers are right at eye level for many people. Be careful when visiting the plant, however, because contact with the sap can cause burns to the skin when exposed to sunlight.

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Ants, flies, wasps and other insects can be readily found visiting the large nectaries of open flowers.

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Although these particular ants were fairly small, large ants such as Formica and Camponotus were also seen on wild parsnip flowers.

What are the ants doing on the plants besides collecting nectar? Wild parsnips are considered to be invasive weeds in many areas. Therefore, ants feeding on nectar might considered to be favorable if they interfere with the plants' success or might be unfavorable if the ants protect the plants from herbivores. Jing Yang and Dana Dudle from the Biology Department at DePauw University studied the effects of ants on the reproductive success of wild parsnip by excluding flying versus crawling insects from certain flowers. In their limited investigation they found no differences in plant fitness whether ants were present or not, but suggested further studies needed to be done.

Regardless, if you are interested in watching ants you should keep your eye out for wild parsnip flowers.

Ave you ever seen ants on wild parsnip?

When you are searching for ants, what plants do you look for?

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