This is not a bull!
One of the 'biggest' pest is a bull in a field where there is a right of way.
So learn to identify a bull!.

It sounds like your entering a real jungle if you pack your things and stray off into the beautiful country side of Britain. All sorts of pests can trouble your stay. They come in different shapes and sizes, however mostly in one size: small!

Be aware of ...

Midges. Never in short supply. They come in clouds and can make camping, or stopping to take a good look at the beautiful scenery a terrible experience, especially between June and August. They are active in calm, warm and humid conditions but a light breeze will keep them away. Bear this in mind when selecting a camp site. Use a good insect repellant, or repellant candles to keep them away. Midges can spoil your stay/walk/holiday!
See for midges information the
Undiscovered Scotland website or the Wikipedia entry on this flying insect. And don't be fooled, Scottish midges are as annoying as those in the north of England!

Ticks. Can be a nasty problem, avoid sitting in deep grass or bracken. If its a good year for ticks make it a habit to inspect yourself before bedtime. Be aware of infections! Lyme, often a result from a tick bite can be deadly! Take a look at CDC Lyme Disease web page as it contains a huge amount of information. You may also have a look at the Wikipedia entry on ticks which includes some photographs.

Horse flies or clegs can give a nasty bite. Again the Wikipedia entry contains some useful background information.

Bulls. Learn to identify a bull because there is a marked difference between bulls, cows and bullocks (castrated bulls). If you see a bull alone in a field where there is a right of way, it is probably there illegally and you will have to find your way around the field. If it is there with cows it is there probably legally. Cows and bullocks may rush up you in a field but an aggressive, charging bull in a field you have the right to cross is dangerous.