I went out into the garden last night and found that there were a lot of tiger black swallowtail caterpillars on my fennel (I always thought they were tigers, but a check online shows that that's not the species). They're eating my fennel, but that's fine with me; I don't actually eat my fennel plants - they're just as decorative plants - so if the caterpillars want to eat them, I don't care.

There's a variety of different sizes of caterpillars out there; there must have been several "hatches"







They differ slightly in color patterning. I'm not sure why - there seem to be different caterpillar "morphs" but just one color pattern of black swallowtail.

I just hope the red wasps don't get them this year like they did in the past.

I counted about 19 caterpillars on my plants (I have 3 largish fennel plants). I don't have an exact count because the caterpillars don't like being handled or moved.

If you get too close to them, they have a defense mechanism - they have "horns" (they look kind of like "angry eyebrows") that come out of their head, and they make a bad smell. (They are actually a type of gland and their real name is "osmeterium." But I'd rather think of them as "angry eyebrows")

I tried to get a picture of the caterpillar horns; in this shot they're partially retracted already:



There's also a YouTube video showing the process: