wasp
A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder ...
in the family
Trichogrammatidae
The Trichogrammatidae are a family of small endoparasitoid wasps in the superfamily Chalcidoidea that include some of the smallest of all insects, with most species having adults less than 1 mm in length, with species of '' Megaphragma'' ...
. It contains some of the smallest known insects, '' Megaphragma caribea'' (170 μm) and ''
Megaphragma mymaripenne
''Megaphragma mymaripenne'' is a very small wasp. At 200 μm ( mm; inch) in length, it is the third-smallest extant insect, comparable in size to some single-celled organisms. It has a highly reduced nervous system, containing only 7,400 n ...
'' (200 μm), which are roughly the same size as some
unicellular
A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Organisms fall into two general categories: prokaryotic organisms and ...
protozoans
Protozoa (: protozoan or protozoon; alternative plural: protozoans) are a polyphyletic group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic debris. Historically ...
.
External morphology
The body is very compact, and its length can range from 0.16 to 0.3 mm. The
mesosoma
The mesosoma is the middle part of the body, or tagma, of arthropods whose body is composed of three parts, the other two being the prosoma and the metasoma. It bears the legs, and, in the case of winged insects, the wings.
Wasps, bees and a ...
is rather high and is mostly shorter than the
metasoma
The metasoma is the posterior part of the body, or tagma (biology), tagma, of arthropods whose body is composed of three parts, the other two being the prosoma and the mesosoma. In insects, it contains most of the digestive tract, respiratory sy ...
, and the
prothorax
The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum (dorsal), the prosternum ( ventral), and the propleuron (lateral) on ...
is very short. The scutellum is shorter than the mid lobe of the mesoscutum, and has a pair of
setae
In biology, setae (; seta ; ) are any of a number of different bristle- or hair-like structures on living organisms.
Animal setae
Protostomes
Depending partly on their form and function, protostome setae may be called macrotrichia, chaetae ...
. The
metathorax
The metathorax is the posterior of the three segments in the thorax of an insect, and bears the third pair of legs. Its principal sclerites ( exoskeletal plates) are the metanotum (dorsal), the metasternum (ventral), and the metapleuron (lateral ...
is slightly shorter than the
propodeum
Propodeum labelled within the alitrunk of an ant worker
The propodeum is a term that can refer to unrelated structures in insects or in mollusks.
Insects
The first abdominal segment in Apocrita Hymenoptera (wasps, bees and ants) is known a ...
. The propodeal spiracle is in an oval groove and near the internal margin with 2 very small setae. The legs are robust and have striate sculpture on the coxae.
Head
The head is
hypognathous
This glossary of entomology describes terms used in the formal study of insect species by entomologists.
A–C
A synthetic chlorinated hydrocarbon insecticide, toxic to vertebrates. Though ...
and rounded, being slightly flattened in the
longitudinal
Longitudinal is a geometric term of location which may refer to:
* Longitude
** Line of longitude, also called a meridian
* Longitudinal engine, an internal combustion engine in which the crankshaft is oriented along the long axis of the vehicle, ...
direction
antero-posteriorly
Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provi ...
, and with a slightly concave posterior surface. The head capsule has only 1 barely noticeable post-occipital ridge, and several folds near the base of the antennae, and other sutures are absent. The hypostome and
clypeus
The clypeus is one of the sclerites that make up the face of an arthropod. In insects, the clypeus delimits the lower margin of the face, with the labrum articulated along the ventral margin of the clypeus. The mandibles bracket the labrum, but ...
aren't distinguishable from each other and hypostomal bridge is missing. The keyhole-shaped occipital foramen is small, and the
tentorium
The tentorium (plural tentoria) is a term used to refer to the framework of internal supports within an arthropod head. The tentorium is formed by ingrowths of the exoskeleton, called apodeme
An exoskeleton () . is a skeleton that is on the ex ...
has
anterior
Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...
and posterior arms, with the
dorsal
Dorsal (from Latin ''dorsum'' ‘back’) may refer to:
* Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism
* Dorsal, positioned on top of an aircraft's fuselage
The fus ...
arms reduced in size. The tentorial bridge is present, but the laminatentoria are absent. The occipital area has many folds that reduce the skull's size from
pupae
A pupa (; : pupae) is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their life cycle, the stages th ...
to adults.
Eyes
Its compound eyes are lateral and consist of roughly 30
ommatidia
The compound eyes of arthropods like insects, crustaceans and millipedes are composed of units called ommatidia (: ommatidium). An ommatidium contains a cluster of photoreceptor cells surrounded by support cells and pigment cells. The outer part ...
and have 3
ocelli
A simple eye or ocellus (sometimes called a pigment pit) is a form of eye or an optical arrangement which has a single lens without the sort of elaborate retina that occurs in most vertebrates. These eyes are called "simple" to distinguish the ...
.
Antennae
The antennae are inserted at mid-level of the orbital line and are approximately 150 μm long. It has a short radicle, and the scape is usually elongate and slightly curved. The