Overiiearing 



Cricket 

 Love Songs 



Some flies bear an eary 

 resemblance to their victims 



by Daniel Robert and 

 Ronald R. Hoy 



For 200 million years, on any warm 

 evening, male crickets have been eagerly 

 rubbing their forewings together, 

 "singing" to attract mates. Early on, they 

 were pioneers, inventing new ways to ad- 

 vertise their presence to their feUow crick- 

 ets. But about forty milUon years ago, their 

 serenades began to attract some eaves- 

 dropping newcomers — tachinid flies. For 

 crickets, this was bad news. 



Tachinid flies are parasitoids, parasites 

 that use an animal host as a food source for 

 their young, although the adults are free- 

 living. The female tachinid fly, a tiny crea- 

 ture, deposits her eggs or larvae on or near 

 a host insect, typically a species much 

 larger than herself, such as a beetle or a 

 caterpillar. The larvae then burrow inside 

 and gorge themselves on the host's gener- 

 ous muscular mass or other tissues. After a 

 week or so, they emerge to pupate. This 

 strategy is very successful, judging by the 

 abundance of tachinid fly species (8,000 

 have been identified worldwide, 1,000 in 

 North America alone). The family Tachi- 

 nidae is the second largest in the order of 

 true flies, Diptera, after the very diverse 

 Tipulidae, or crane flies. Another success- 

 ful, large family of parasitoids is the Sar- 

 cophagidae, or flesh flies, which counts 

 some 2,000 species worldwide. 



As far as we know, the vast majority of 

 tachinid flies (like nearly all flies) are deaf 

 to high-pitched sounds, such as the chirp- 

 ing and trilling of crickets, and find their 

 hosts by sight and smell. But a few species 

 of tachinid flies have evolved the abiUty to 



home in on a cricket's chirp, getting the 

 drop on their victim, no matter how well it 

 may be concealed by vegetation or the 

 darkness of night. 



Among them is the fly Ormia ochracea, 

 which lives along the gulf coast from 

 Florida to Texas, preying on the south- 

 western or southeastern field cricket. Div- 

 ing out of the night sky, the fly deposits 

 one or more tiny maggots on or near a 

 chirping male cricket and takes off. The 

 active maggots latch on to the cricket and 

 penetrate it. (They may even end up para- 

 sitizing a female cricket attracted by the 

 same song.) By the time the maggots have 

 matured and are ready to emerge, the 

 cricket is at death's door. 



As biologists interested in the evolution 



After feasting for a week to ten days on 

 the muscle mass of a living cricket, a 

 larva of the tachinid fly Ormia ochracea 

 emerges to pupate. 



Marie Read: Cornell University 



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