I agree with Benni. Horrible creature. I raise Monarch Cats in the hope of saving them from those flys. I lose so many Monarch Cats due to their killer larvae.

It is a sad fact that, yes, there are a few species of tachinid flies that do lay eggs in monarch caterpillars (including the invasive non-native species, Compsilura concinnata, as well as a small handful of native tachinid fly species). However, there are over 1300 species of tachinid flies native to North America that do not attack monarch caterpillars and do very good work to control many common pests of farm and garden plants. I encourage you to re-read the section above titled Tachinid Flies and Butterfly Caterpillars to better understand how the two groups interact. Understanding how humans have impacted the natural balance of both of these insects is important, too. Native species of tachinid flies deserve to exist just as much as the monarchs do. Saying they don’t is like saying a lion doesn’t deserve to exist just because it feeds on a gazelle.