Being without knowledge of central American biology, all I can say is that it is a member of the family Vespidae, which includes the Hornets. It is some species of paper wasp, most probably in the genus Polistes. The Vespidae include nearly all social wasps (definitely including those in the photograph), including the various hornets of the Northern hemisphere. (Not counting bees, which are from some pooints of view a subset of the wasps.) The wasps in the picture however,  seem to be fairly clearly in the subfamily Polistinae, wasps that build naked, single-decker paper combs. They are not the only ones to do so, though most of the species that do so are in this subfamily. Polistes species are extremely widespread in the warmer parts of all continents (apart from Antarctica  of course!)

I  cannot argue with the Belizeans of course, but most Polistes are fairly reserved with polite visitors who do not crowd them, though it is a good idea to keep a few metres from their nests and not to move too suddenly. As a rule, by the time they attack they already have expressed their disapproval by turning towards the intruder and limbering their wings ready for use. Away from their nests they tend to be quite docile, but if this species is as virulent as reported, I suppose the locals might understandably be nervous. As I expect never to encounter the species, but have several times been led to skip nimbly when thoughtlessly grabbing or brushing past nests of other species of Polistes or of Belonogaster (without any alarming symptoms, such as throat constriction), I shall accept their assessment with polite reserve. Usually such symptoms suggest hypersensitive victims.

Thanks for the picture,

Jon

That is a really cool photograph!  Thank you for sharing on the Last Word.

Are there any entomologists that can chime in as well? 

This does appear to be a paper wasp, genus Polistes.  In Europe these are relatively small, not more than 20 mm long.  Nevertheless their sting is quite painful.  I live in an area where Hornets are plentiful, for instance the Asian hornet which has recently been introduced to Europe is a frequent visitor to my garden, so I am very much aware of how much larger a hornet is compared to a common wasp.  It is twice the length and consequently has eight times the volume; and most likely then can deliver eight times the volume of venom.  A hornet sting is said to very painful and if delivered on the head or neck, particularly dangerous. If Nicky's wasp really is 5 cm long, which I doubt however, it is going to be equally dangerous.

From the photo I am not able to make an identification with any certainty.  The commonest Central American paper wasp is Polistes canadensis, the Red Paper Wasp.  It appears to me that this is what we have here.  I found photographic evidence of the swelling which Polistes metricus, another paper moth of the Americas, can produce and one can see that on the neck this would be worrying.  I can imagine that you would want to avoid being stung by P. canadensis, even though as Jon writes they would normally leave you alone.

It also occurs to me that in view of the fact that most people cannot distinguish a bat from a badger any wasp-like creature will become a 'strangler wasp' to the locals, and the true culprit might be a local species of  hornet.