Megarhyssa, also known as giant ichneumonid wasps, giant ichneumons, or stump stabbers,[ Bug of the Month July 2014: Female Stump Stabbers laying eggs!!!, What's That Bug. Accessed 2015-06-07] is a genus of large Ichneumonidae, with some species known for having the longest of any . They are idiobiont ectoparasitoids
Geographical range and habitat
Megarhyssa species occur all over the world.
There are only four
Megarhyssa species known to inhabit the
Nearctic realm region inhabiting
Deciduous forests.
They are widespread across the United States, and Canada.
The species
M. macrurus,
M. atrata, and
M. greenei are known to be
Sympatry in the northeastern United States.
M. macrurus is known to inhabit further southern regions as well, reaching Mexico.
M. nortoni has been introduced to South Africa, Australia, and New Zealand as a biological control agent.
Description and identification
Megarhyssa male adults reach body lengths going from 2.3 to 3.8 cm (0.9 to 1.6 inches), while female adults can measure from 3.5 to 7.5 cm (1.5 to 3 inches).
Both sexes can be distinguished because females have an extremely slender, and long organ to lay eggs called the
ovipositor. This organ is much longer than the body itself, its length can range from 5 to 10 cm (2 to 4 inches).
adults show variation in coloration, including dark brown, bluish black, reddish brown and/or bright yellow.
Species of the United States and Canada
The species
M. atrata (Fabricius) shows a bright yellow head, and an almost completely black body.
The wings are black as well. It can be easily distinguished from the species
M. macrurus,
M. greenei, and
M. nortoni, which show yellow and brown striped color patterns that resemble one another, requiring identification by specialists.
Ecology
The family
Ichneumonidae is composed of
. The adults do not often feed. When they do so, they feed on water droplets found on leaves that often contain
nectar.
The
Larva feed on flesh from hosts the adults locate. In the Nearcctic, Palearctic, and Australian regions, some
Megarhyssa species such as
M. emarginatoria,
M. jezoensis, and
M. nortoni are
of
woodwasps.
The species
M. atrata,
M. macrurus, and
M. greenei show
diurnality activity and have undergone allopatric speciation and attack the
Larva of one species of woodwasp:
Tremex columba.
These three species are capable of coexisting with each other because their
Ovipositor have different lengths.
As a result, they find their host at different depths within trees, or logs. The distance the
larva is within the trunk is equal to the length of the ovipositor of each species. The ovipositor of
M. atrata is known to puncture up to 14 cm inside the wood, and such length makes this
wasp functionally the longest species in the order
Hymenoptera (if ovipositor is included).
Reproduction
Reproductive cycle
The reproductive cycle of
Megarhyssa begins with the female locating a
larva of
Tremex columba inside the bark of a tree. She lays an egg close by or on the
larva, the
Megarhyssa larva devours it, it
Pupa under the bark, and emerges the following year as an adult.
Males often emerge first. The species
M. atrata,
M. macrurus, and
M. greenei share their territory, and habitat, showing the same behavior: males emerge, and remain close by the trees where more
Wasp from these species emerge.
Megarhyssa males often try to squeeze inside the holes of the bark of trees even before females emerge because preemergence mating is easier to carry out than postemergence mating.
Mate choice and competition
Megarhyssa males have been known to detect other individuals to emerge before the emergence happened. Males of the three species aggregate around the hole to find out the
sex of the individual.
Males do so hearing how the females bite, and chew through the wood to find their way out. If the individual is a male, many males often show little interest, and fly away. In case it is a female, males try to
Mating with her as soon as possible. The
sensory organs that allow the
Wasp to detect their mates, and hosts is close to the antennae.
Evolution of flight
The movement that flight makes possible for
Parasitoid is crucial to reproduce, so it is related directly with fitness.
In
M. nortoni, it is known females perform longer single flights and overall longer flights than males. It is thought this is because females are the individuals that reach new habitats, redistribute the progeny, and locate hosts. These activities require longer-range flights.
Males of
M. nortoni spend most of their time in aggregations around sites from which females are about to emerge.
Even if males are disturbed and fly away from the site, they return and regroup around the same point of the tree. They have been known to be flying around a specific tree and patrolling it over time. Such features lead to the evolution of shorter-range flights.
Species
Species within the genus:
-
Megarhyssa arisana
-
Megarhyssa atomistica
-
Megarhyssa atrata
-
Megarhyssa aurantia
-
Megarhyssa babaulti
-
Megarhyssa belulliflava
-
Megarhyssa bicolor
-
Megarhyssa bonbonsana
-
Megarhyssa cultrimacularis
-
Megarhyssa fulvipennis
-
Megarhyssa gloriosa
-
Megarhyssa greenei
-
Megarhyssa hainanensis
-
Megarhyssa indica
-
Megarhyssa insulana
-
Megarhyssa jezoensis
-
Megarhyssa laniaria
-
Megarhyssa lenticula
-
Megarhyssa longitubula
-
Megarhyssa macrurus
-
Megarhyssa middenensis
-
Megarhyssa mirabilis
-
Megarhyssa nortoni
-
Megarhyssa obtusa
-
Megarhyssa perlata
-
Megarhyssa praecellens
-
Megarhyssa recava
-
Megarhyssa rixator
-
Megarhyssa rotundamacula
-
Megarhyssa strimacula
-
Megarhyssa superba
-
Megarhyssa taiwana
-
Megarhyssa vagatoria
-
Megarhyssa verae
-
Megarhyssa weixiensis
-
Megarhyssa wugongensis
External links
