There are multiple metric units to choose from! This tutorial goes through the process of choosing the best metric unit to use for measuring the mass of a given object.
The most common aphids on houseplants are the light green ones (pear aphids), but aphids can also be found colored pink, white, grey and black. Additionally, winged aphids can appear when colonies are established and fly to infect new plants. Juvenile aphids (nymphs) look like smaller versions of the adults.
Best Answer: They are all wasps. The difference is in the pattern. Yellow jackets are a wide variety of black and yellow wasps. Hornets I believe are black and white. And wasp covers hornets, yellow jackets, and every other wasp. Interestingly, some of what are commonly called bees in the U.S. are actually yellow jackets. As they lack the characteristic wasp waist, and are the same size as honey bees, it's an easy mistake to make.