Never drink from an open can on the golf course, for that matter outside. I have known two people who did, one drinking cola, and the other beer. Both were stung by bees/hornets. One died from asphyxiation, due to swelling in the mouth throat areas; the other thought he was having a heart attack and learned at the emergency room he had swallowed a hornet, and it had stung him in his throat/lung area. That is why most courses serve beverages from iced cups with lids!
For the gnats in PA and the Sand Fleas in NJ try dryer sheets...rub them over the bill of your hat on the underside to keep them out of your eyes...they are seeking moisture. The smoke from cigars is effective also.

Come and play some of the courses in South Africa. Depending which course every thing from snakes, hippos, lions, crocodiles, monkeys, baboons (Sun City million dollar) and plenty of zebras. You name we have it.
Best advice is keep the ball where the lawn mower goes and you will be OK.

Mosquitoes in South Florida in July and August. Gotta wear long pants, and mosquito repelant for your exposed arms.

Hey fellow duffers - watch out for the snakes in Guernwood, Ca. Northwood is a great place to play long greens. But there is diamond back Timber rattlers here. I have seen one right close to my ball at the 4th hole. These snakes will not bother you unless you cross their path. We do have paper wasps in the trees, an scorpions under rocks.
Life is dangerous so are live balls flying the wrong way!

Ditto on the no-seeums, S.Carolina in the Spring--they itch worse than any ivy.
Black flies in the adirondacks in Spring--(May-June) There is no spray/cigar etc. to combat these blood drawing critters..

Pretty much the same here in Oklahoma as in Texas; with the addition of chiggers.

No-see-ums (Small flesh eating knats) are also a problem in S.C. around Kiawah and other courses in the area. Birds are a problem in Oklahoma around Altus and Lawton. They will literally attack you if you're too close to their nest.

In Texas they have ground so hard in the rough it will break your wrist. In Guam and the Pacific Islands they have coral on the sides of the fairway that will literally cut through your club; I have scars to prove it.

If you play in the Northeast, ticks are a real problem. I contracted Lyme disease from a tick bite while in Martha's Vineyard. Luckily, I caught it and got treated. Not treated, you can have lifelong nervous system damage. Be ultra careful if playing at a course with fescue, heather or other high grasses.