As I attempt to kill ants in my yard, I've been reading various claims about how to kill ants without common consumer chemical pesticides like DEET. One claim that I've heard repeatedly is that rice, corn meal or flour can make an ant's stomach explode.

From Wikihow, "How to Kill Ants Without Pesticides":

Wheat flour and dried rice (any kind) also work. Like corn meal, it expands in their stomach and bursts them, resulting in a death slightly less nasty than being boiled alive.

In another post, someone suggests the same method with Grits. From Yahoo Answers "Will pouring boiling water on an ant hill kill the ants?":

...Also another way to kill ants is... grits. I'm not lying! Just sprinkle some grits over the hill and the ants eat it and something in grits makes the ants stomach expand and explode.

The problem is that people are really attracted to the dramatic idea of having a pest creature explode, so I have to wonder if these are true statements.

Can rice or flour actually kill ants, and does it really make their stomachs explode?

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    Something you can try to kill ants, is to get light soda/lemonade, or whatever with sugar substitute sweeteners. I know my dad does that... actually that probably warrants its own question. If you want to kill the ants without really controlling the population really(like if you have them somewhere you don't want them), then use soap mixed with water. It kills them, I used to experiment with all sorts of things like that as a kid, and soap+water worked wonders. – Wertilq Jun 3 '13 at 11:10
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    I'm glad skeptics.SE overall caught my bug of ant extermination :) – user5341 Jun 3 '13 at 13:19
  • I had great luck with a mix of very hot water and ammonia. – Pieter B Jan 3 '14 at 15:10
  • Borax mixed with sugar will kill ants. – iantresman Jan 24 '15 at 13:49
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    The pedant in me points out if the advice about wheat flour or dry rice in "How to Kill Ants Without Pesticides" worked, they would be a pesticides, by definition. – Oddthinking Jun 24 '15 at 8:51

Probably not. There doesn't appear to be any evidence of the exploding stomach phenomenon. And most evidence to be found points in the opposite direction.

Seeds are a natural food source.
This is a study of the diet of one type of Ant in Oklahoma. And seeds are listed as an important dietary item.

At grassland and pasture sites, seeds (17.2 and 15.7%, respectively) were important foraged items.

Is grain substantially different than flour for ants?
The size of the particles swallowed must be smaller than typical flour. http://www.ijera.com/papers/Vol2_issue3/KZ2318391842.pdf https://www.ars.usda.gov/sp2UserFiles/Place/60360510/publications/Glancey_et_al-1981(M-1351).pdf Almost all wheat flour particles are larger than the esophagus of the ant (~45µm).

Can ants eat solid food? Regurgitate?
THE INFRABUCCAL POCKET OF A FORMICINE ANT: A SOCIAL FILTRATION DEVICE http://downloads.hindawi.com/journals/psyche/1962/025068.pdf
This paper goes into how the ants feed, if I may summarize. The ants feed on liquid food (workers, at least, can't feed on solid food). Relatively large solid pieces are caught in a special cavity, when this cavity is full, the particles are ejected as a single pellet. The filtered food is regurgitated and shared with other workers, who in turn also filter the food.

Actual measurements made with species of Formica, fed on food labelled with radioactive tracer, have shown that the crop contents from single foragers may become shared by an entire colony in a matter of hours (Wilson and Eisner, I957).

Anything Else? The closest I could find about feeding flour in particular to ants just involved using it as bait for collecting specimens. No mention of exploding stomachs was made.

Meat, flour and sugar baits were used on the soil surface and buried to examine species composition of the ant fauna in three separate tropical forests in Brazil, and to control for the effect of the regional faunal pool.

Caveats These papers look mostly at the worker caste of the red imported fire ant. Results could be different for different types of ants. This assumes nothing special about the flour besides being ground seed.

Conclusion, Making the assumption that the reason people think their stomachs will explode is because the rice/flour will expand once in contact with water, rupturing the stomach (violently?), I think I have presented enough evidence to show that this won't be the case. The food must already be in contact with water before consumption. Seeds are naturally eaten by ants. Ants constantly regurgitate their food to share with each other.

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    This answer contains a conjecture that suffers from the Fallacy of Division. Although flour is made of seeds, it has different physical properties (e.g. the different surface areas means flour can explode if ignited, where grains won't. Flour is more cohesive with water than grains.) – Oddthinking Jan 22 '15 at 23:23
  • @Oddthinking Thank you for pointing this out. Do you have any suggestions on how I can improve the answer? I agree that this doesn't "settle it" which is why I didn't feel ok with stopping there. Do you think it would be helpful to explicitly mention the caveat? Or is there additional research you can suggest that could improve the answer? (I'm still learning this site) – Adam Phelps Jan 23 '15 at 0:52
  • @Oddthinking I've overhauled this answer. Can you let me know if your concerns are now addressed? – Adam Phelps Jan 23 '15 at 7:55

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