Equity security when used in sections 44-3,107 to 44-3,114 shall mean (1) any stock or similar security, (2) any security convertible, with or without consideration, into such a security or carrying any warrant or right to subscribe to or purchase such a security, (3) any such warrant or right, or (4) any other security which the Director of Insurance deems to be of similar nature and considers necessary or appropriate, by such rules and regulations as he or she may adopt and promulgate in the public interest or for the protection of investors, to treat as an equity security.