Page:First course in biology (IA firstcourseinbio00bailrich).pdf/308



away and credit given the student on a regular scale. Thus will grading and marks be placed to encourage intelligent study of nature rather than book or laboratory cram. One per cent to be added to the final grade may be credited for every species of pupa, every rare insect (with an observed fact as to its habits) brought in, every bird migration observed, every instance of protective coloration, mimicry (p. 146), outwitting of enemy, instance of injurious insects, and how to combat them, etc. Sharp eyes and clear reasoning will then count as much on school grades as a memory for words or mechanical following of laboratory directions. On scale of 100, class work = 50, examination = 25, field work = 25.

Collecting Insects.—In cities and towns insects, varying with the season, are attracted by electric lights. Beetles and bugs will be found under the lights, moths on posts near the lights, grasshoppers and crickets and other insects in the grass near by. A lamp placed by a window brings many specimens. In the woods and in rocky places insects are found under logs and stones, and under the bark of dead trees. In open places, prairies, meadows, and old fields with grass and flowers, it will be easy to find grasshoppers, butterflies, and some beetles. Ponds and streams are usually rich in animal forms, such as bugs and beetles, which swim on or under the surface, and larvæ of dragon flies crawling on the bottom. Dragon flies and other insects that lay eggs on the water are found flying in the air above. (In the spring, newly hatched crawfish, tadpoles, and the eggs of frogs and toads should also be collected, if found.) Moths may be caught at night by daubing molasses or sirup made from brown sugar upon the trunks of several trees, and visiting the trees at intervals with a lantern.

An insect net for catching butterflies and for dredging ponds may be made by bending a stout wire into a circle one foot in diameter, leaving enough straight wire to fasten with staples on an old broomstick. To the frame is fastened a flour sack, or cone made of a piece of mosquito netting.

Butterflies and moths should be promptly killed, or they will beat their wings to pieces. The quickest method is by dropping several drops of gasoline upon the ventral (under) side of the thorax and abdomen. (Caution: Gasoline should never be used near an open fire, or lamp, as explosions and deaths result from the flame being led through the gasoline-saturated air to the vessel containing it.)