A stinging is someone who is unauthorised to travel
The term "spinal" (or "spines") comes from the shipping and it means that someone without paying as a passenger goes on a boat (or an airplane). It is sometimes called a blind passenger. A stinging is often someone who has no money for the crossing or who (unnoticeably) wants to flee the country (or wants to enter a country). Because a flight or boat trip can often take a long time, the spine must take enough food and drink and not be noticed while travelling. On a large ship with many passengers it is often easier: food is in stock and there are enough people around to not stand out. The sea is sometimes overboarded, but this is forbidden. The rule is that the captain demands the freight price, and if the spine cannot pay for it then it may be expected that he is doing labor. The captain must ensure that the stinging is given sufficient nutrition and medical care (if necessary).