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Dogs are widely used by the police as biological recognition systems to detect drug smuggling and drug caches. Yet recent evidence suggests that insects, rather than mammals, might be used more effectively in this capacity. In the 1950s, German biologist Dietrich Schneider developed the first method that enabled researchers to record activity in insect olfactory nerves and to identify the compounds or class of compounds that trigger a particular behavioral response. The position of the insect olfactory organs on the surface of its body allows for direct investigation of the system`s response. Schneider`s technique formed the foundation of an olfactory detection system based upon insects, a system that is at least as effective as the ones based upon mammals.

Insects have olfactory systems that are very similar to those of vertebrates. Insects first detect odors via finger-like protuberances on the antenna, called olfactory sensilla. The odorant molecules pass through pores in the outer cuticle of the sensilla and become attached to an odorant-binding protein. This protein carries the hydrophobic molecules through the lymph fluid found inside the cell and attaches them to receptors on the dendritic projections of a sensory nerve cell. Finally, these receptors send signals to the central nervous system, allowing researchers to detect and interpret the responses.

Which of the following statements can be most reasonably inferred from the passage?

  • ASome police departments have already tested using insects to detect smuggling.
  • BThe use of dogs to detect smuggling dates back to the nineteenth century.
  • CDetection of signals sent by the receptors to the central nervous system is easier in insects than in mammals.
  • DIn the first half of the twentieth century, there was no reliable method for recording the activity in insect olfactory nerves and identifying the compounds that trigger a behavioral response.
  • EThe position of the insect olfactory organs on its body varies between flying insects and crawling insects.
正确答案: D

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