The neurobiology of cricket song.

Nowadays few people live where they can hear crickets singing on summer evenings, but makers of motion pictures know that nothing evokes a bucolic mood more effectively than the sound of crickets chirping in the background. Cricket song, which may seem like a random sequence of chirps and trills, is actually a communication system of considerable complexity. As Richard D. Alexander of the University of Michigan and others have shown, each species of cricket has a distinctive repertory of several songs that have evolved to transmit messages of behav­ ioral importance. From the work of many laboratories, including our own at the University of California at Berkeley and at Cornell University, it is known that the nerve networks needed for generating the songs of crickets are closely allied to those involved in flight. Both systems de­ velop in stages as the cricket passes through its growth cycle from the larva to the adult. Through breeding experi­ ments it has also been shown that the distinctive song patterns of various spe­ cies are not learned behavior but are en­ coded in the insect's genes. Thus we have found that hybrids produced by mating different species exhibit song pat­ terns that are intermediate between those of the parents. Progress is also be­ ing made in discovering the genes that control the song patterns and finding where they are located among the crick­ et's chromosomes. Ultimately it should be possible to piece together all the links in the chain from a sequence of chemical units in the DNA of the cricket's genes to the specification of a nerve network that leads to the production of a distinc­ tive song. Cricket song is only one exam­ ple of animal behavior that has a large genetically determined component.