flies on green and white anthurium

i am puzzled as to why the green and white anthurium seems to attract this particular species of flies. the peculiar thing is that when the spadix is green, you do not see any of these flies. the flies are attracted to the spadix when it turns white or beige.

i also realise that when the spadix is green, the spathe is also green and when the spadix turns white, the spathe changes likewise. the spathe is the hood-like bract found alongside the spadix.

(for victor's information, i took sometime to recall the name of this plant. i only found out when i visited hort park on 20 sept. as for the name 'spadix', i google image for anthurium and found it. just in case, you still do not believe i am not a 'boh terr ni' person.)