Trichopoda pennipes
Encyclopedia
Trichopoda pennipes is a fly
in the family Tachinidae
. The larvae are parasitoids of several true bugs
, particularly squash bug
s and leaf-footed bugs in the family Coreidae
and stinkbugs in the familye Pentatomidae
and it is used as a biological control agents for these agricultural pests. It is native to North and South America and has been introduced into southern Europe.
. It has a black head with large brown eyes, a mostly black thorax
, a bright orange abdomen
, transparent smoky wings with prominent veins, black legs and yellow feet. The hind legs bear a comb-like fringe of short hairs. Male flies have a dark spot on the wings and females have a dark tip to the abdomen.
. It may be seen hovering over other plants in search of suitable bugs on which to lay its eggs, most commonly squash bugs and southern green stinkbugs. The female fly lays several small, pale-coloured, oval eggs
on a large nymph
or an adult bug. When the eggs hatch, the larvae burrow into the bug. If there are several larvae in one host, only one survives. After feeding on the bug's tissues, the cream-coloured larva emerges and falls to the ground where it pupates in a reddish-brown pupa
rium formed from the last larval skin. The bug meanwhile dies. After about two weeks, an adult fly emerges from the pupa. After mating, a female fly may lay several hundred eggs in total. There are up to three generations of the fly each year and the parasitoid overwinters as a second instar
larva within the body of the overwintering host
.
. This is a crop pest that originated in Ethiopia
but now has a worldwide distribution and is named for the foul-smelling defensive secretion it exudes from a gland on its thorax. This exudate appears to be fairly effective in preventing predation by birds but is well tolerated by T. pennipes which seems to be highly attracted by an aggregation pheromone
produced by the male bugs. This results in a higher proportion of males being parasitised than females.
There seems to be different biotypes across the United States
, preying on different hosts in different regions. In northern California
, a population of the fly parasitised the bordered plant bug, Largus succinctus, but did not attack the squash bug, Anasa tristis. In an experiment, T. pennipes was collected from squash fields in New York State
and released near squash fields in California. The insects targeted the squash bugs and established permanent populations. Their eggs are now found deposited on nearly 50% of the squash bugs in the area but it is unclear how effective this is in controlling the crop pests. On the southern green stink bug, the rate of parasitism can be as high as 93% and up to 80% on the squash bug. However, T. pennipes does not prevent all crop damage as the bugs continue to feed and reproduce after being parasitised, though the reproductive organs begin to atrophy when the parasitoid reaches the second instar stage. Control of the pest is more effective when nymphs are parasitised since half of these die before becoming adults and any that overwinter will die before laying eggs.
Diptera
Diptera , or true flies, is the order of insects possessing only a single pair of wings on the mesothorax; the metathorax bears a pair of drumstick like structures called the halteres, the remnants of the hind wings. It is a large order, containing an estimated 240,000 species, although under half...
in the family Tachinidae
Tachinidae
Tachinidae is a large and rather variable family of true flies within the insect order Diptera, with more than 8,200 known species and many more to be discovered. There are over 1300 species in North America. Insects in this family are commonly called tachina flies or simply tachinids...
. The larvae are parasitoids of several true bugs
Hemiptera
Hemiptera is an order of insects most often known as the true bugs , comprising around 50,000–80,000 species of cicadas, aphids, planthoppers, leafhoppers, shield bugs, and others...
, particularly squash bug
Squash bug
Anasa tristis of the family Coreidae is a major pest of squash and pumpkins, and is a vector of the cucurbit yellow vine disease bacterium...
s and leaf-footed bugs in the family Coreidae
Coreidae
Coreidae are a large family of predominantly herbivorous insects that belong in the hemipteran suborder Heteroptera. There are more than 1,800 species in over 250 genera. They vary in size from 7 to 45 mm, making the larger species some of the biggest heteropterans. The body shape of coreids...
and stinkbugs in the familye Pentatomidae
Pentatomidae
Pentatomidae, Greek pente meaning five and tomos meaning section, is a family of insects belonging to order hemiptera that includes some of the stink bugs and shield bugs. Their antennae are 5-segmented, which gives the family its scientific name. Their bodies are usually shield-shaped...
and it is used as a biological control agents for these agricultural pests. It is native to North and South America and has been introduced into southern Europe.
Morphology
This fly is about the size of a large houseflyHousefly
The housefly , Musca domestica, is a fly of the suborder Cyclorrhapha...
. It has a black head with large brown eyes, a mostly black thorax
Thorax (insect anatomy)
The thorax is the mid section of the insect body. It holds the head, legs, wings and abdomen. It is also called mesosoma in other arthropods....
, a bright orange abdomen
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
, transparent smoky wings with prominent veins, black legs and yellow feet. The hind legs bear a comb-like fringe of short hairs. Male flies have a dark spot on the wings and females have a dark tip to the abdomen.
Life cycle
Trichopoda pennipes first appears in the late spring or early summer and feeds on nectar sucked from flowers such as Queen Anne's lace and meadowsweetSpiraea
Spiraea , is a genus of about 80-100 species of shrubs in the family Rosaceae, subfamily Spiraeoideae. They are native to the temperate Northern Hemisphere, with the greatest diversity in eastern Asia....
. It may be seen hovering over other plants in search of suitable bugs on which to lay its eggs, most commonly squash bugs and southern green stinkbugs. The female fly lays several small, pale-coloured, oval eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
on a large nymph
Nymph (biology)
In biology, a nymph is the immature form of some invertebrates, particularly insects, which undergoes gradual metamorphosis before reaching its adult stage. Unlike a typical larva, a nymph's overall form already resembles that of the adult. In addition, while a nymph moults it never enters a...
or an adult bug. When the eggs hatch, the larvae burrow into the bug. If there are several larvae in one host, only one survives. After feeding on the bug's tissues, the cream-coloured larva emerges and falls to the ground where it pupates in a reddish-brown pupa
Pupa
A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...
rium formed from the last larval skin. The bug meanwhile dies. After about two weeks, an adult fly emerges from the pupa. After mating, a female fly may lay several hundred eggs in total. There are up to three generations of the fly each year and the parasitoid overwinters as a second instar
Instar
An instar is a developmental stage of arthropods, such as insects, between each molt , until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, or...
larva within the body of the overwintering host
Host (biology)
In biology, a host is an organism that harbors a parasite, or a mutual or commensal symbiont, typically providing nourishment and shelter. In botany, a host plant is one that supplies food resources and substrate for certain insects or other fauna...
.
Use in biological control
One of the principal host species for Trichopoda pennipes is the southern green stinkbug, Nezara viridulaNezara viridula
Nezara viridula, commonly known as the southern green stink bug or green vegetable bug , is a plant-feeding stink bug. Although believed to have originated in Ethiopia, it can now be found around the world...
. This is a crop pest that originated in Ethiopia
Ethiopia
Ethiopia , officially known as the Federal Democratic Republic of Ethiopia, is a country located in the Horn of Africa. It is the second-most populous nation in Africa, with over 82 million inhabitants, and the tenth-largest by area, occupying 1,100,000 km2...
but now has a worldwide distribution and is named for the foul-smelling defensive secretion it exudes from a gland on its thorax. This exudate appears to be fairly effective in preventing predation by birds but is well tolerated by T. pennipes which seems to be highly attracted by an aggregation pheromone
Pheromone
A pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual...
produced by the male bugs. This results in a higher proportion of males being parasitised than females.
There seems to be different biotypes across the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, preying on different hosts in different regions. In northern California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, a population of the fly parasitised the bordered plant bug, Largus succinctus, but did not attack the squash bug, Anasa tristis. In an experiment, T. pennipes was collected from squash fields in New York State
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
and released near squash fields in California. The insects targeted the squash bugs and established permanent populations. Their eggs are now found deposited on nearly 50% of the squash bugs in the area but it is unclear how effective this is in controlling the crop pests. On the southern green stink bug, the rate of parasitism can be as high as 93% and up to 80% on the squash bug. However, T. pennipes does not prevent all crop damage as the bugs continue to feed and reproduce after being parasitised, though the reproductive organs begin to atrophy when the parasitoid reaches the second instar stage. Control of the pest is more effective when nymphs are parasitised since half of these die before becoming adults and any that overwinter will die before laying eggs.