The beetles or _Coleoptera_ (sheath wings), often mistaken for bugs by the uneducated, have the first pair of hardened wings meeting in a straight line in the middle of the back, the second pair of wings being covered by them. Beetles are frequently found on goldenrod blossoms in the fall. Other forms of life, especially _spiders_, which have four pairs of walking legs, _centipedes_ and _millepedes_, both of which are wormlike and have many pairs of legs, may be found. Try to discover members of the six different orders named above. Collect specimens and bring them to the laboratory for identification. Why do Insects live on Plants?--We have found insect life abundant on living green plants, some visiting flowers, others hidden away on the stalks or leaves of the plants. Let us next try to find out _why_ insects live among and upon flowering green plants. The Life History of the Milkweed Butterfly.--If it is possible to find on our trip some growing milkweed, we are quite likely to find hovering near, a golden brown and black butterfly, the monarch or milkweed butterfly (_Anosia plexippus_). Its body, as in all insects, is composed of three regions. The monarch frequents the milkweed in order to lay eggs there. This she may be found doing at almost any time from June until September. Egg and Larva.--The eggs, tiny hat-shaped dots a twentieth of an inch in length, are fastened singly to the underside of milkweed leaves. Some wonderful instinct leads the animal to deposit the eggs on the milkweed, for the young feed upon no other plant. The eggs hatch out in four or five days into rapid-growing wormlike caterpillars, each of which will shed its skin several times before it becomes full size. These caterpillars possess, in addition to the three pairs of true legs, additional pairs of _prolegs_ or caterpillar legs. The animal at this stage is known as a _larva_. Formation of Pupa.--After a life of a few weeks at most, the caterpillar stops eating and begins to spin a tiny mat of silk upon a leaf or stem. It attaches itself to this web by the last pair of prolegs, and there hangs in the dormant stage known as the _chrysalis_ or _pupa_. This is a resting stage during which the body changes from a caterpillar to a butterfly. [Illustration: Monarch butterfly: adults, larvae, and pupa on their food plant, the milkweed. (From a photograph loaned by the American Museum of Natural History.)] The Adult.--After a week or more of inactivity in the pupa state, the outer skin is split along the back, and the adult butterfly emerges. At first the wings are soft and much smaller than in the adult. Within fifteen minutes to half an hour after the butterfly emerges, however, the wings are full-sized, having been pumped full of blood and air, and the little insect is ready after her wedding flight to follow her instinct to deposit her eggs on a milkweed plant.