Ticks are insects

False. Ticks are classified in the class Arachnida, subclass Acari (together with mites (2)), order Parasitiformes, and suborder Ixodida (3).

A feature that distinguishes arachnids from insects is the presence of four pair of legs in adult arachnids compared to three pair of legs in insects (2). However, the larval stage of I. ricinus ticks do have 6 legs.

A review on the characteristics that distinguish  insects from ticks can be found in “Ticks are not Insects: Consequences of Contrasting Vector Biology for Transmission Potential” (59). Comparing insects to ixodid ticks it can be found that insects are highly mobile, have several blood  meals, feed on many different hosts per generation and have repeated reproduction associated with blood meal periodicity and the fecundity (number of eggs) is variable.  Ixodid ticks have low mobility (dispersion is dependent on hosts), take only one  blood meal per life stage, feed on (at most) three different hosts per generation and have a single oviposition (egg laying process) per generation, during which however they lay thousands of eggs.