Which of the following structures helps in distinguishing male cockroaches from female cockroaches?

Hind wings of mosquitoes are termed as

Answer in one word or one line.
Give the common name of $Periplaneta \text{ } americana$.

In which of the following is the wings vestigial?

Which of the following statement$(s)$ is/are correct?
$(i)$ Cockroaches are brown or black bodied animals that are included in class $Insecta$ of phylum $Arthropoda$.
$(ii)$ Males bear a pair of short,thread-like anal styles which are absent in females.
$(iii)$ The heart of a cockroach consists of an elongated muscular tube lying along the mid-dorsal line of the thorax and abdomen.
$(iv)$ The nymph grows by moulting about $13$ times to reach the adult form.

Cockroach belongs to the class