3. Viruses may harm host cells. A vaccine is one way that infection from viruses can be controlled. Why can't a vaccine help people already infected with a virus?

Use this dichotomous key for insect identification to identify the insect shown. 1. a. insect has one pair of wings. order diptera b. insect has two pairs of wings. go to #2 2. a. front wings thicker in texture than hind wings go to #3. b. front and hind wings are same texture throughout. go to #4 3. a. front wings are short order dermaptera b. front wings cover entire abdomen order coleoptera 4. a. wings with scale on all parts of their area. order lepidoptera b. wings without scales go to #5. 5. a. hind wings smaller than front wings. order ephemeroptera b. front and hind wings nearly equal in size. order odonata the insect pictured is in the order diptera. ephemeroptera. coleoptera. odonata.