The term
wasp is typically defined as any
insect of the order
Hymenoptera and suborder
Apocrita that is neither a
bee
nor
ant. Almost every pest insect species has at
least one wasp species that preys upon it or parasitizes it, making
wasps critically important in natural control of their numbers, or
natural
biocontrol.
Parasitic wasps are increasingly used in
agricultural
pest control as they prey
mostly on pest insects and have little impact on crops.
Taxonomy
The majority of wasp species (well over 100,000 species) are
"parasitic" (technically known as
parasitoids), and the
ovipositor is used simply to lay eggs, often
directly into the body of the host. The most familiar wasps belong
to
Aculeata, a
division of
Apocrita, whose ovipositors are adapted into a
venomous sting, though a
great many aculeate species do not sting. Aculeata also contains
ants and bees, and many wasps are commonly mistaken for bees, and
vice-versa. In a similar respect, insects called "velvet ants" (the
family
Mutillidae) are technically
wasps.
The suborder
Symphyta, known commonly as
sawflies, differ from members of Apocrita by
lacking a sting, and having a broader connection between the
mesosoma and
metasoma. In addition to this, Symphyta
larvae are mostly
herbivorous
and "
caterpillarlike", whereas those of
Apocrita are largely
predatory or
parasitoids.
A much
narrower and simpler but popular definition of the term wasp is any
member of the aculeate family Vespidae, which
includes (among others) the genera known in North America as yellowjackets (Vespula and
Dolichovespula) and hornets
(Vespa); in many countries outside of the Western
Hemisphere
, the vernacular usage of wasp is even further
restricted to apply strictly to yellowjackets (e.g., the "common wasp").
Categorization
The various
species of wasps fall into one
of two main categories: solitary wasps and social wasps. Adult
solitary wasps generally live and operate alone, and most do not
construct nests (below); all adult solitary wasps are fertile. By
contrast, social wasps exist in colonies numbering up to several
thousand strong and build nests—but in some cases not all of the
colony can reproduce. In the more advanced species, just the wasp
queen and male wasps can mate, whilst the majority of the colony is
made up of sterile female workers.
Characteristics

Spider Hunting Wasp,
heterodotonyx
bicolor, and prey
Image:Wasp morphology.png|thumb|250px|The basic morphology of a
female Yellowjacket wasp|rightpoly 1011 964 642 889 891 517 1192 1
1603 28 1595 28 1231 821
Wingsrect 80
1066 347 1582
Antennarect 524 946
963 1352
Thoraxpoly 365 1599 363 1471 554
1361 966 1373 1340 1438 1757 1618 1742 1809 1340 1806 1015 1597
Legsrect 353 876 508 1358
Headpoly 1511 1478 1660 1319 1784 1578
Stingerpoly 980 1348 991 1005 1207 892 1643 1286
1494 1474 1214 1384
Abdomenrect 0 0 1896
1815
Female Yellowjacketdesc
bottom-leftThe following characteristics are present in most wasps:
- Two pairs of wings (except wingless
or brachypterous forms in all female Mutillidae, Bradynobaenidae, many male Agaonidae, many female Ichneumonidae, Braconidae, Tiphiidae,
Scelionidae, Rhopalosomatidae, Eupelmidae, and various other families).
- An ovipositor, or stinger (which is only present in females
because it derives from the ovipositor, a female sex organ).
- Few or no thickened hairs (in contrast to
bees); except Mutillidae, Bradynobaenidae, Scoliidae.
- Nearly all wasps are terrestrial; only a few specialized
parasitic groups are aquatic.
- Predator or parasitoids, mostly on other terrestrial insects;
most species of Pompilidae (e.g. tarantula hawks), specialize in using
spiders as prey, and various parasitic wasps use spiders or other
arachnids as reproductive hosts.
Wasps are critically important in natural
biocontrol. Almost every pest insect species has
at least one wasp species that is a predator or parasite upon it.
Parasitic wasps are also increasingly used in agricultural
pest control. Wasps also constitute an
important part of the
food chain.
Biology
Genetics
In wasps, as in other
Hymenoptera,
sexes are significantly
genetically different. Females have a
diploid (2n) number of
chromosomes and come about from fertilized eggs.
Males, in contrast, have a
haploid (n)
number of chromosomes and develop from an unfertilized egg. Wasps
store sperm inside their body and control its release for each
individual egg as it is laid; if a female wishes to produce a male
egg, she simply lays the egg without fertilizing it. Therefore,
under most conditions in most species, wasps have complete
voluntary control over the sex of their offspring.
Anatomy and gender
Anatomically, there is a great deal of variation between different
types of wasp. Like all insects, wasps have a hard
exoskeleton covering their three main body
parts. These parts are known as the
head,
metasoma and
mesosoma. Wasps also have a constricted region
joining the first and second segments of the abdomen (the first
segment is part of the mesosoma, the second is part of the
metasoma) known as the
petiole.
Like all insects, wasps have three sets of two legs. In addition to
their
compound eyes, wasps also have
several simple eyes known as
ocelli. These
are typically arranged in a triangular formation just forward of an
area of the head known as the
vertex.
It is possible to distinguish between certain wasp species genders
based on the number of divisions on their
antennae. Male Yellowjacket wasps for
example have 13 divisions per antenna, while females have 12. Males
can in some cases be differentiated from females by virtue of the
fact that the upper region of the male's mesosoma (called the
tergum) consists of an additional terga. The total number
of terga is typically six. The difference between sterile female
worker wasps and queens also varies between species but generally
the queen is noticeably larger than both males and other
females.
Wasps can be differentiated from bees, which have a flattened hind
basitarsus. Unlike bees, wasps
generally lack plumose hairs. They vary in the number and size of
hairs they have between species.
Diet
Generally wasps are
parasites or
parasitoids as larvae, and feed only on nectar as
adults. Many wasps are predatory, using other insects (often
paralyzed) as food for their larvae. A few social wasps are
omnivorous, feeding on a variety of fallen fruit, nectar, and
carrion. Some of these social wasps, such as yellowjackets, may
scavenge for dead insects to provide for their young. In many
social species the larvae provide sweet secretions that are fed to
the adults.
In parasitic species, the first meals are almost always provided by
the animal that the adult wasp used as a host for its young. Adult
male wasps sometimes visit flowers to obtain
nectar to feed on in much the same manner as
honey bees. Occasionally, some species, such as
yellowjackets, invade
honey bee nests and steal
honey and/or
brood.
Wasp parasitism
With most species, adult
parasitic
wasps themselves do not take any
nutrients from their prey, and, much like
bees,
butterflies, and
moths, those that do feed as adults typically
derive all of their nutrition from nectar. Parasitic wasps are
typically
parasitoids, and extremely
diverse in habits, many laying their eggs in inert stages of their
host (
egg or
pupa), or sometimes paralyzing their prey by injecting
it with venom through their
ovipositor.
They then insert one or more eggs into the host or deposit them
upon the host externally. The host remains alive until the
parasitoid
larvae are mature, usually dying
either when the
parasitoids pupate, or when they emerge as adults.
Nesting habits

Various wasp nests
The type of nest produced by wasps can depend on the species and
location. Many social wasps produce paper pulp nests on trees, in
attics, holes in the ground or other such sheltered areas with
access to the outdoors. By contrast solitary wasps are generally
parasitic or predatory and only the latter build nests at all.
Unlike
honey bees, wasps have no
wax producing
glands. Many
instead create a paper-like substance primarily from wood pulp.
Wood fibers are gathered locally from weathered wood, softened by
chewing and mixing with saliva. The pulp is then used to make combs
with cells for brood rearing. More commonly, nests are simply
burrows excavated in a substrate (usually the soil, but also plant
stems), or, if constructed, they are constructed from mud.
Solitary wasps
The nesting habits of solitary wasps are more diverse than those of
social wasps.
Mud daubers and
pollen wasps construct mud cells in sheltered
places typically on the side of walls.
Potter wasps similarly build vase-like nests
from mud, often with multiple cells, attached to the twigs of trees
or against walls. Most other predatory wasps burrow into soil or
into plant stems, and a few do not build nests at all and prefer
naturally occurring cavities, such as small holes in wood. A single
egg is laid in each cell, which is sealed thereafter, so there is
no interaction between the larvae and the adults, unlike in social
wasps. In some species, male eggs are selectively placed on smaller
prey, leading to males being generally smaller than females.
Social wasps
The nests of some social wasps, such as hornets, are first
constructed by the queen and reach about the size of a walnut
before sterile female workers take over construction. The queen
initially starts the nest by making a single layer or canopy and
working outwards until she reaches the edges of the cavity. Beneath
the canopy she constructs a stalk to which she can attach several
cells; these cells are where the first eggs will be laid. The queen
then continues to work outwards to the edges of the cavity after
which she adds another tier. This process is repeated, each time
adding a new tier until eventually enough female workers have been
born and matured to take over construction of the nest leaving the
queen to focus on reproduction. For this reason, the size of a nest
is generally a good indicator of approximately how many female
workers there are in the colony. Social wasp colonies often have
populations exceeding several thousand female workers and at least
one queen.
Polistes and some
related types of paper wasp do not construct their nests in tiers
but rather in flat single combs.
Social wasp reproductive cycle (temperate species only)

A young paper wasp queen founding a
new colony
Wasps do not reproduce via mating flights like bees. Instead social
wasps reproduce between a fertile queen and male wasp; in some
cases queens may be fertilized by the sperm of several males. After
successfully mating, the male's
sperm
cells are stored in a tightly packed ball inside the queen. The
sperm cells are kept stored in a dormant state until they are
needed the following spring. At a certain time of the year (often
around autumn), the bulk of the wasp colony dies away, leaving only
the young mated queens alive. During this time they leave the nest
and find a suitable area to
hibernate
for the winter.
First stage
After emerging from hibernation during early summer, the young
queens search for a suitable nesting site. Upon finding an area for
their colony, the queen constructs a basic wood fiber nest roughly
the size of a walnut into which she will begin to lay
eggs.
Second stage
The sperm that was stored earlier and kept dormant over winter is
now used to
fertilize the eggs being
laid. The storage of sperm inside the female queen allows her to
lay a considerable number of fertilized eggs without the need for
repeated
mating with a male wasp. For this
reason a single female queen is capable of building an entire
colony from only herself. The queen initially raises the first
several sets of wasp eggs until enough sterile female workers exist
to maintain the offspring without her assistance. All of the eggs
produced at this time are sterile female workers who will begin to
construct a more elaborate nest around their queen as they grow in
number.
Third stage
By this time the nest size has expanded considerably and now
numbers between several hundred and several thousand wasps. Towards
the end of the summer, the queen begins to run out of stored sperm
to fertilize more eggs. These eggs develop into
fertile males and fertile female queens. The male
drones then fly out of the nest and find a mate thus perpetuating
the wasp
reproductive cycle. In
most species of social wasp the young queens mate in the vicinity
of their home nest and do not travel like their male counterparts
do. The young queens will then leave the colony to hibernate for
the winter once the other worker wasps and founder queen have
started to die off. After successfully mating with a young queen,
the male drones die off as well. Generally, young queens and drones
from the same nest do not mate with each other; this ensures more
genetic variation within wasp
populations, especially considering that all members of the colony
are theoretically the direct genetic descendants of the founder
queen and a single male drone. In practice, however, colonies can
sometimes consist of the offspring of several male drones. Wasp
queens generally (but not always) create new nests each year,
probably because the weak construction of most nests render them
uninhabitable after the winter.
Unlike honey bee queens, wasp queens typically live for only one
year. Also queen wasps do not organize their colony or have any
raised status and
hierarchical power
within the social structure. They are more simply the reproductive
element of the colony and the initial builder of the nest in those
species which construct nests.
Social wasp caste structure

A wasp gathering wood fibers
Not all social wasps have castes that are physically different in
size and structure. In many
polistine paper
wasp and
stenogastrines, for
example, the castes of females are determined behaviorally, through
dominance interactions, rather than having caste predetermined. All
female wasps are
potentially capable of becoming a
colony's queen and this process is often determined by which female
successfully lays eggs first and begins construction of the nest.
Evidence suggests that females compete amongst each other by eating
the eggs of other rival females. The queen may, in some cases,
simply be the female that can eat the largest volume of eggs while
ensuring that her own eggs survive (often achieved by laying the
most). This process theoretically determines the strongest and most
reproductively capable female and selects her as the queen. Once
the first eggs have hatched, the subordinate females stop laying
eggs and instead forage for the new queen and feed the young; that
is, the competition largely ends, with the losers becoming workers,
though if the dominant female dies, a new hierarchy may be
established with a former "worker" acting as the replacement queen.
Polistine nests are considerably smaller than many other social
wasp nests, typically housing only around 250 wasps, compared to
the several thousand common with yellowjackets, and stenogastrines
have the smallest colonies of all, rarely with more than a dozen
wasps in a mature colony.
Common families
References
- Norman F. Johnson, Charles A. Triplehorn. 2004. Borror's
Introduction to the Study of Insects. 7th Edition.
See also
External links
Sister projects