The Bee and the Butterfly

The bee and the butterfly.
One's a beneficial insect. That would "bee" the honey bee. The other is a yellow and white butterfly, striking in appearance, but in its larval stage, it's a major pest of alfalfa.
We don't normally see them sharing lavender in our pollinator garden in Vacaville, but there they were.
The bee appeared determined. The butterfly looked skittish.
Which one left the lavender first? The butterfly. 
On his research website, butterfly guru Art Shapiro, UC Davis distinguished professor of evolution and ecology, describes the alfalfa butterfly, aka orange sulphur butterfly, as "one of commonest (in Central California), often reaching very high densities in alfalfa fields in midsummer to autumn."  When the alfalfa is cut, it "may emigrate en masse, even flooding into cities. This is also our most variable butterfly, seasonally and individually."
The eggs, laid singly, are red, and the larva are "basically green with a white-and-pink line on each side, but may have very variable black markings as well. The pupa is apple-green with rosy highlights."

Shapiro, a 50-year member of the UC Davis faculty, says that "Although it is a significant alfalfa pest, this butterfly overwinters as a larva almost entirely in annual vetch at low altitudes, and colonizes alfalfa only as the vetch senesces in May-June. Aside from alfalfa and annual vetches, it also breeds on a variety of clovers and sweet clovers and occasionally on lupines." 

The UC Statewide Integrated Pest Management Program (UC IPM) says the butterflies "lay eggs on the new growth of alfalfa that is less than 6 inches tall. Eggs hatch into green caterpillars in 3 to 7 days. Full-grown caterpillars are about 1.5 inches long and are distinguished from other caterpillars on alfalfa by their velvety green bodies with white lines along their sides. "There are four to seven generations per year of alfalfa caterpillar, and each generation is closely synchronized with the hay-cutting cycle so that the caterpillar pupates before cutting occurs." See more information on the UC IPM website.