Dawn2 wrote:
I say that all you should do is seal up where they're getting in. They don't deserve to be killed just because they are in the wrong place at the wrong time. Because flies are animals. And killing animals is cruel. And if people only care about being nice to cute and cuddly animals, they aren't true animal lovers at all. *nods seriously* So I say find where they're getting in or do nothing.
Flies aren't animals, they're insects.
housefly
housefly, common name of the fly Musca domestica, found in most parts of the world. The housefly, a scavenger, does not bite living animals but is dangerous because it carries bacteria and protozoans that cause many serious diseases, e.g., typhoid fever, cholera, and dysentery. The housefly feeds by depositing a drop of digestive liquid on its food, which may be garbage, excrement, or other filth. Although most of the liquid drop is sucked back again through the insect's tubelike lower lip, or labium, a residue remains that may contain disease-causing organisms from previous meals. Disease is also transmitted on the fly's sticky foot pads and hairy body. Each female lays from 100 to 200 eggs in the garbage or manure on which the white larvae feed. With favorable temperatures, one generation or more per month may be produced. Metamorphosis is complete, i.e., development is in four stages. The housefly is classified in the phylum Arthropoda, class Insecta, order Diptera, family Muscidae. For methods of control see bulletins of the U.S. Dept. of Agriculture.
Not only does the point of entry have to sealed, but the flys that are already in the house have to be killed. I wouldn't be willing to risk diseases/fly larva just to avoid being called cruel.
On the subject of spiders... my grandma lives out in the country and has wolf spiders that live in her house. She doesn't kill them even though she doesn't like spiders because they control the flies and other various insects.