Cockroaches
Parts of this information was taken from the http://en.wikipedia.org/wiki/Cockroach
 Cockroaches are insects of the order Blattodea, sometimes also called Blattaria, of which about 30 species out of 4,600 total are associated with human habitats. About four species are well known as pests.
Among the best-known pest species are the American cockroach, Periplaneta americana, which is about 30 mm (1.2 in) long; the German cockroach, Blattella germanica, about 15 mm (0.59 in) long; the Asian cockroach, Blattella asahinai, also about 15 mm (0.59 in) in length; and the Oriental cockroach, Blatta orientalis, about 25 mm (0.98 in). Tropical cockroaches are often much bigger, and, contrary to popular opinion, extinct cockroach relatives and 'roachoids' such as the Carboniferous Archimylacris and the Permian Apthoroblattina were not as large as the biggest modern species.
Cockroaches determine whether or not food is safe by using their sensory systems. However, these sensory systems are able to quickly adapt to environmental changes.
How they are able to detect the presence of poison in food that was once considered to be "safe" - according to their sensory systems - is still a mystery.
Researchers at North Carolina State University looked at a species of cockroaches that have adapted and avoided traps coated in sugar, they were able to determine the mechanism of this change.
Cockroaches have tiny little hair-like sensors on their mouths which they use to "taste" food, activating sensors house gustatory receptor neurons, or GRNs. Certain GRNs activate in the presence of food that is sugary - which makes them feed - as opposed to GRNs that activate in the presence of food that is bitter - making the animal avoid the food.
The research, which started in the mid-1980s, found that German cockroaches given baits incorporating a stimulant (glucose) and a deterrent (insecticide) evolved a behavioral change called "glucose aversion".
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