Haller&#39;s organ can be found on the first pair of legs. It is a sense organ that helps the tick to find its host. Ticks detect the host&#39;s temperature, humidity and carbon dioxide concentration. Haller&#39;s organ also contains small sensory hair, the setae.
The slide shows the tick "Ixodes dammini" which is known to transmit Lyme disease in the USA. Ticks feed on the blood of host animals (including humans) and are therefore able to spread diseases. Ticks are related to the spiders and are therefore not insects.