At first I thought they might be monarch butterfly larvae, but after some fast google searches I found out the difference - the queen butterfly larvae have an extra row of "horns". I've never successfully raised butterflies on my own, so I was hesitant to take them in as a pet project. What changed my mind was that they were both already in their fifth instar (a time in-between molting and growing), which is their last instar before forming their chrysalis. The other turning point was that the bush I found them on was devoid of their normal food source, and both would have potentially died, anyway.
(The second caterpillar - note the three sets of horns and the small, yellow aphids on the branch)
The first caterpillar was larger and formed its chrysalis within a week. The second one, while in its last stage, still needed more food to grow. Unfortunately, I couldn't find any more living desert milkweed plans and thought for sure it was going to starve to death. It got smaller and smaller every day, up until I spotted three more bushes (covered in hemiptera such as aphids) by the light rail station. The diet of the queen butterfly caterpillar consists of milkweed leaves and blooms, so finding three healthy, blossoming plants made me super happy. Overnight the caterpillar seemed to double in size, and within a few days it also formed its chrysalis:
Yesterday night my fiancé and I noticed it starting to darken up, and this morning we awoke to a beautifully emerged butterfly.
Both butterflies were released in memory of my father- the first two days before Father's Day, and the second this afternoon. :)
