ive just bought 2 female 10 week old guinea pigs yesterday, they are in their outside hutch and of course they are scared still but they are starting to explore and are very nice and vocal at times! well i was giving them some grass today by hand (i know to not fuss them to much for a week or so) and as they came close and startingg to eat the grass my grey Abyssinian was itching and i can spot them little extremely tiny black flies/bugs on her, they are outside the cage aswell, i will purchase some fly spray thats safe for them asap but will they harm my guinea pigs in any way? thankyou .