By Whitney Cranshaw, Colorado State University
Cooperative Extension, Entomology

One of the most common
questions regarding insect classification surrounds the differences between the various
stinging wasps and bees.  This is a good taxonomic question that gets a bit muddled from
the common names that are applied to this diverse group of insects. 

First of all bees and wasps are
members of the order Hymenoptera, along with ants and a few "weirdo" groups
including sawflies and horntails.  Essentially all bees develop on a diet of pollen and
nectar.  Also, they are almost always hairy bodied, a morphological boost for pollen
collecting. 

The most well known are social bees
that produce a colony including the honeybee ( Apis mellifera) that
produce a perennial colony and bumble bees (Bombus spp.) 
that annually establish new colonies.  However there are many types of solitary bees
-species that have the habit of individually creating a colony that is dug into the ground
or excavated from some soft substrate. ( Of course, in these cases the female does all the
nest construction work and provisioning of the young.)  Leafcutter bees (usually Megachile spp.)  and various digger bees are examples of species that have this habit.  All of
the above rear their young on nectar and pollen, the few exceptions to this habit among
Colorado bees are those that are parasites of other bees. 

The definition of a "wasp"
gets a bit dicier.  Perhaps the best separation between almost all Colorado bees and wasps
are their feeding habits and "body hair".  All wasps develop as a predator or
parasite of other insects or are scavengers.  Wasps have generally a minor role in pollination (primarily done by
the males) and have a comparatively much less "hairy" body than bees. 

But then there are wasps and there
are wasps.  They are categorized at this level as: 1) parasitic wasps; 2) solitary hunting
wasps; and 3) social wasps. 

The parasitic wasps lay their
eggs in or on some insects. ( Species in the families Braconidae and Ichneumonidae are
particularly commonly encountered.)  Their young develop on the unfortunate host, almost
invariably killing it.  Although females often have a long, scary looking stinger (which is
used primarily to lay eggs in some insects they are non-aggressive and produce little, if
any, pain if a sting does occur. 

The solitary hunting wasps primarily
involve two families of wasps, Sphecidae and Pompilidae.  General habits of both are in many ways similar.  The female creates rearing cells in some sort of nest,
goes out and collects prey that she paralyzes and returns it to the nest cell, then, when
the nest cell is adequately provisioned, lays an egg and seals it.  The type of nest
depends on the species. 

Some hunting wasps dig into soil,
others create mud nests and many excavate the pith of hollow plants.  One of the main
differences of the two families are that the Sphecid wasps hunt insects; pomipilids hunt
spiders.  Also different is the sting - some of the pompilid wasps have about the most
painful sting of any insect, while the sphecid wasps have a mild sting. 

Then there are the social wasps (all
in the family Vespidae), that are the group that most encounter human in unfortunate
stinging incidents.  All the social wasps share some habits: colonies are established
annually, abandoned completely and dying off in fall after leaving a few fertilized queens
to scatter around the vicinity and attempt a new colony the next season; nests are made of
"paper" produced from masticated wood pulp; populations of colonies show
dramatic differences in activity during the growing season, as they annually increase
exponentially from late May through September; and they dont leave a stinger, as do
honey bees. 

Basically there are three groups of
social wasps.  The most common are the yellowjackets, accounting for the overwhelming majority of stinging
incidents in the state (see above).  These are all in the genus Vespula and the most
noxious species is the western yellowjacket (Vespula pensylvanica).  Yellowjackets produce
a paper nest but the site of the nest is concealed, in an abandoned rodent nest below
ground, behind an exterior wall, in hollows of childrens playground equipment, etc. 
Yellowjackets have diverse tastes.  Although they feed on some insects, they readily
scavenge sweets and protein-rich foods.  They can be serous nuisance problems around
uncovered garbage and at outdoor dining areas in late summer. 

Perhaps more commonly observed, but
far less commonly involved in sting incidents are the "hornets".  These make
paper enclosed nests in trees, shrubs and under eaves that may exceed the size of a
football.  They are produced by members of the genus Dolichovespula.  The baldfaced hornet,
a large black and white wasp, is the most commonly encountered member of this group. 
Hornets are primarily predators of other insects, rarely visiting garbage or outdoor
dining areas.  Then there are "umbrella wasps".  These similarly make their nest
cells of a papery material, but do not enclose it with a papery envelope.  Colorado species
that have this habit are in the genera Polistes and Mischosyttarus.  As with the hornet
these have a generally beneficial habit, rearing their young on insects that they capture,
but will sting when defending the hive.