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August 03, 2010

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Cockroaches may share food advice

June 6, 2010
Courtesy of Queen Mary, University of London
and World Science staff

Ev­er won­dered how cock­roaches seem to know the best place to grab a meal? A new Brit­ish study sug­gests that, much like hu­mans, they share their lo­cal knowl­edge of the best food sources and fol­low ‘rec­om­menda­t­ions’ from oth­ers.

It’s of­ten strik­ing how lit­tle we know about our clos­est neigh­bour. Un­til now, it was as­sumed that cock­roaches for­age on their own to find food and wa­ter. But the new study found that groups of the in­sects seem to make a col­lec­tive choice about the best food source, ex­plain­ing why we so com­monly find them feed­ing en masse in the kitch­en late at night.

“Cock­roaches cost the U.K. econ­o­my mil­lions of pounds in wast­ed food and per­ish­a­ble prod­ucts. Bet­ter un­der­stand­ing of how they seek out our food would al­low us to de­vel­op bet­ter pest con­trol meas­ures, which are fre­quently in­ef­fec­tive and in­volve the use of in­sec­ti­cides that can have health side-ef­fects,” said the stu­dy’s au­thor, Ma­thieu Li­ho­reau of Queen Mary, Uni­vers­ity of Lon­don.

The study was pub­lished in the May 18 online issue of the research jour­nal Be­havi­our­al Ecol­o­gy and So­ci­o­bi­ology.

Mathieu and colleagues released hun­gry cock­roaches of the spe­cies Blat­tella ger­man­ica in­to an are­na where they could choose be­tween one of two piles of food. Li­horeau not­ed that, rath­er than choos­ing one ran­domly and split­ting in­to two groups as would be ex­pected if they were act­ing in­de­pend­ent­ly, the ma­jor­ity of the cock­roaches fed solely on one piece of food un­til it was all gone. By fol­lowing in­di­vid­ual in­sects, it al­so emerged that the more of cock­roaches there were on one piece of food, the long­er each one would stay to feed. Through a snow­ball ef­fect, most of the cock­roaches ac­cu­mu­late on one source.

“These ob­serva­t­ions cou­pled with sim­ula­t­ions of a math­e­mat­i­cal mod­el in­di­cate that cock­roaches com­mu­ni­cate through close con­tact when they are al­ready on the food source. This is in con­trast with the hon­ey­bees’ wag­gle dance or ants’ chem­i­cal trails, which are soph­is­t­icated mes­sages that guide fol­lowers over a long dis­tance,” Li­ho­reau said.

“Although we think [cockroaches] sig­nal to oth­er cock­roaches us­ing a ‘for­ag­ing phe­ro­mone,’” or chem­i­cal sig­nal, “we haven’t yet iden­ti­fied it,” he added. Once iden­ti­fied, a man-made ver­sion could be used to im­prove pest con­trol, mak­ing in­sec­ti­cide gels more ef­fective or be used to cre­ate an in­sec­ti­cide-free trap, he not­ed.

Sci­en­tists should “pay more at­ten­tion to cock­roaches and oth­er sim­ple ‘so­ci­eties’ as they pro­vide re­search­ers with a good mod­els for co-opera­t­ion and emer­gent prop­er­ties of so­cial life, that we could ex­trap­o­late to more soph­is­t­icated so­ci­eties, like ours,” said Li­ho­reau.

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Ever wondered how cockroaches seem to know the best place to grab a meal? A new British study suggests that, just like humans, they share their local knowledge of the best food sources and follow ‘recommendations’ from others. It’s often striking how little we know about our closest neighbour. Until now, it was assumed that cockroaches forage on their own to find food and water. But the new study found that groups of the insects seem to make a collective choice about the best food source, explaining why we so commonly find them feeding en masse in the kitchen late at night. “Cockroaches cost the U.K. economy millions of pounds in wasted food and perishable products. Better understanding of how they seek out our food would allow us to develop better pest control measures, which are frequently ineffective and involve the use of insecticides that can have health side-effects,” said the study’s author, Mathieu Lihoreau of Queen Mary, University of London. This study is published in the journal Behavioural Ecology and Sociobiology. In the experiment, hungry cockroaches of the species Blattella germanica were released into an arena where they could choose between one of two piles of food. Lihoreau noted that, rather than choosing one randomly and splitting into two groups as would be expected if they were acting independently, the majority of the cockroaches fed solely on one piece of food until it was all gone. By following individual insects, it also emerged that the more of cockroaches there were on one piece of food, the longer each one would stay to feed. Through a snowball effect, most of the cockroaches accumulate on one source. “These observations coupled with simulations of a mathematical model indicate that cockroaches communicate through close contact when they are already on the food source. This is in contrast with the honeybees’ waggle dance or ants’ chemical trails, which are sophisticated messages that guide followers over a long distance,” Lihoreau said. “Although we think they signal to other cockroaches using a ‘foraging pheromone,’” or chemical signal, “we haven’t yet identified it,” he added. Once identified, a man-made version could be used to improve pest control, making insecticide gels more effective or be used to create an insecticide-free trap, he noted. Scientists should “pay more attention to cockroaches and other simple ‘societies’ as they provide researchers with a good models for co-operation and emergent properties of social life, that we could extrapolate to more sophisticated societies, like ours,” said Lihoreau.