Dichotomous key consists of series of statements that can be used to identify an organism. The statements are in an order that determines broader characteristics first and then moves on to specific characteristics. In this way gradually from a pile of classification, the correct one is narrowed down.
Here, pair of wings were observed first. Since the insect has two pairs of wings, the corresponding action was taken which was to move to step 2. In step two the texture of wings was checked. Our insect has scaly wings which corresponds to 2a. i.e. wings covered in soft scales. Hence, the corresponding order came out to be Lepidoptera .