To squish or not to squish?
The first picture on the left is of a caterpillar egg on a tomato leaf. I suspect it was placed there by a Hummingbird Moth (Hyles species), and will hatch out to be a hornworm.
The second photo is of an Orange Dog caterpillar egg on a lemon leaf. It's the egg of the Giant Swallowtail butterfly.
The Hummingbird Moth and the Swallowtail butterfly are both beautiful bugs; neither in their adult form causes any sort of garden damage, and both provide valuable and desirable pollination in the Desert Garden.
The Orange Dog Caterpillar and the hornworm are both ravenous eaters of plant material and can rapidly defoliate a good area of a given plant. On a quiet evening in the garden, if you get close enough, you can actually hear the hornworm chewing and munching.
As always, our goal is not to control the insect, but to control the amount of unacceptable damage caused by the insect. Chances are that each of these caterpillars will eat about the same amount of foliage, if allowed to hatch and feed. So, we can look at it this way: is the plant going to sustain enough damage from this bug to impair its productivity or appearance?
Given the size of the lemon tree relative to the size of the tomato plant, the hornworm egg got squished, and the Orange Dog was left to hatch.
That won't be the end of it, of course: for every caterpillar egg that we see, there are untold numbers that we don't. Just as well; it keeps life in the garden interesting.