小动物是难以用肉眼观察活体的。如蚜虫、红蜘蛛、草履虫、剑鱼蚤等一般是死后制成装片,在显微镜下放大到几百倍观察,这样由于视野所限,只能见到一部分,往往失掉其真实感,又多占用了课堂时间,当再见到实体时仍然不认识,常常得不到应有的效果。为解决这一问题,笔者在讲棉红蜘蛛时(虫体不超过1毫米),提前二十天把它们养在自己 Small animals are hard to observe with the naked eye. Such as aphids, spider mites, paramecium, swordfish fleas are generally made after the death piece, enlarged to hundreds of times under the microscope observation, so limited because of vision, can only see part of the often lose their true sense, They take up more class time, still do not know when they see the entity again, and often do not get the desired effect. To solve this problem, when I talk about cotton spider mites (parasites no more than 1 mm), twenty days ahead of them to keep themselves