On Friday, I was inspecting the bed that has the cucumber, carrots, and beets in it. I noticed one carrot that needed to be thinned out. It was a late starter and was very close to another, more mature carrot, so I plucked it out. Just before tossing it aside, I noticed a little dark spec on it. It was some kind of larvae or caterpillar. It looked a little bit like a lady bug larvae, but not quite. I discovered about 5 others on the carrots, they weren't on any other plants.
You've probably guessed by the title that what I discovered were the larvae of the black swallowtail butterfly.
So I've been reading up on these guys a little bit. I learned that they lay their eggs on plants in the carrot family, especially carrots (duh), parsley, fennel, dill and Queen Anne's Lace. It amazes me how my 2 rows of carrots, surrounded by decidedly non-carrot plants, were found by these butterflies.
I also learned that butterflies go through growth stages, called instars. I determined that my caterpillars were in their 1st instar.
1st Instar black swallowtail larvae on carrot.
I admit I was concerned about what they would do to my plants. I am used to garden enemies that I do not care about conserving whatsoever (think earwigs, ants, slugs) if it comes to my veggies or them. I do not use chemicals but there are many other ways to get rid of pests. I was faced with a clash between two things I value. I really did not want to lose my crop of carrots. I also would not want to harm the swallowtail's chances. So I did the only reasonable thing, nothing :)
I decided to just see how things progressed and my plan B was to buy some parsley and relocate them to a corner of the yard. Well, the next day I could only find three of the caterpillars and they were already looking larger than the evening before. But the carrots seemed to only have minimal damage. I don't think it's enough to do long term damage at this point.
Today when I checked on them I was sad to find only one caterpillar. But the one left is truly amazing! I can't believe how much they change in such a short period of time.
2nd or 3rd instar black swallowtail caterpillar.
First thing tomorrow I am going to put a nice solid stick in the bed to give this guy a place to form a chrysalis. I've read they rarely do it on carrots because they are not all that sturdy but if you provide another stick they will often use that. Stay tuned for further developments.