The West Coast Lady (Vanessa annabella) is another member of the brush-foot butterfly family, the Nymphalidae. This one looks so much like the Painted Lady that if you don't look really carefully at the markings on the tips of the forewings OR at the dots on the hindwings, chances are you will think you are looking at a Painted Lady! This little WCL landed onn my teeny little potted Hollyhock and I had thought it was a PL. Thank goodness my camera was handy and I was able to capture its image.
The West Coast Lady is a small-to-medium-sized butterfly (1 1/2" to 2 1/4") that is found throughout the western and mid-western United States. It utilizes many of the same host plants as the Painted Lady (Vanessa cardui) which is why it is easily confused! So, if you have various plants in the mallow family (Malvaceae) which includes my favourite Lavatera maritima (tree mallow) or the common Cheeseweed then you just might find these beauties flying around! They also utilize Hollyhock (Althea), Checkerbloom (Sidalcea), and Bush mallow (Malvastrum) for host plants. Here's a close-up shows the detail of the West Coast Lady.
Note that the difference between the WCL and the PL is that the WCL has an orange bar on that forewing (the PL's is white) and four brilliant blue dots on the hindwings (PLs have dark spots that are more brownish-black). These two markings are the easiest way to quickly determine which 'Lady' you have visiting in the garden.
Interestingly enough, the eggs of these two 'Lady' butterflies are so similar it is near impossible to determine which is which! The light green, somewhat barrel-shaped eggs have thin lines so that they look somewhat like a watermelon. They are a laid, usually, on the upper-sides of the host plant's leaves (although eggs have been found on the undersides, on flower blossoms, and on the stems!). 
Here's a strange example of a mama who laid one egg on TOP of another! Here's another picture of a LOT of eggs that have been laid on a small Cheeseweed leaf...
Now, the West Coast Lady is usually found flying throughout the year in California but in other areas, it may be found in the summer and fall. The life-cycle is simple: mama oviposits on the host plant and within a week, the caterpillar hatches. After eating its shell, it goes on to search for the best leaf it can find (often NOT the one it was actually laid on!). The larva goes through a number of molts and looks quite different from the earliest instar to the later instar.
A young WCL caterpillar is dark in colour. Its bristles are apparent even at the earliest stages of its life. When it feels threatened, it will curl up. This curling continues throughout the caterpillar's life.
As it grows and molts, changes in colour are most apparent. Unlike the Painted Lady, this one has such diverse changes that it is fun to watch!
After approximately two weeks of eating and pooping the West Coast Lady larvae looks for a place to pupate. It will hang upside-down in the 'J' position, molt for the last time, toss off its head capsule, and voíla! A pupa! A chrysalis! Now, for approximately two weeks, it will be undergoing metamorphosis and then a pretty butterfly will soon eclose.The pupa is somewhat similar to that of the Painted Lady although the major difference is the two white spots that look like eyes.
