While the genus Hymenoepimecis contains eight described species of parasitoid wasp that range across tropical Mexico and Cuba through southern Brazil, Hymenoepimecis argyraphaga is found only in Costa Rica. (Gauld, 2000)
The parasitoid wasp Hymenoepimecis argyraphaga is found throughout Costa Rica. An example of suitable habitat for H. argyraphaga is an African oil palm plantation near Puntarenas Province, where its host spider, Plesiometa argyra (also known by the taxonomic designation Leucauge argyra), also occurs.
The habitat requirements for H. argyraphaga include sources of food for the adult wasps, mating sites, and a stable population of spider hosts for oviposition. As in other parasitoid wasp species, the adult diet consists of sugar and nectar. Hymenoepimecis argyraphaga typically mates on leaf tips, so the species prefers heavy vegetation. The cocoon webs spun by the spider hosts often are found deep in the undergrowth, where they are sheltered from heavy rains and winds that may otherwise dislodge the cocoons and kill H. argyraphaga. Habitat fragmentation can negatively affect H. argyraphaga populations by separating the wasp from its host spiders. (Eberhard, 2000a; Eberhard, 2001; Shaw, 2006)
Hymenoepimecis argyraphaga adults have forewings that are 6 to 14 mm long and vary in color. The wings can be completely black, orange with black markings, patterned with black and yellow, or translucent. The wasp has a black head; slender mandibles that are yellowish brown; large eyes; long, thin antennae; and thin legs (foreleg size varies among individuals).
The sexual dimorphism in H. argyraphaga is due in part to its egg-laying behavior, which requires the female to grasp its host, sting it, and lay an egg on the abdomen of the host spider. Hymenoepimecis argyraphaga females have well-adapted ovipositors for properly handling eggs and stinging hosts. The ovipositor is not used for laying eggs, but rather to sting, kill, and remove the larvae or eggs of other wasps that previously had laid eggs on a selected host. The ovipositor structure can be straight or slightly upturned, and the ovipositor typically is 1 to 1.4 times longer than the hind tibia. The end of the ovipositor shaft narrows to a distinctly thin point. In addition, females have claws with a large basal lobe, while males have simple claws.
Cocoons often are pale yellow, but have been observed as bright orange in some cases. The color of the cocoon grows darker with time, and the larva is just visible through the thin walls of the cocoon. (Eberhard, 2000b; Gauld, 2000)
An adult female of the wasp Hymenoepimecis argyraphaga immobilizes its host spider, Plesiometa argyra, by injecting it with venom from its ovipositor. Afterward, the wasp glues an egg to the abdomen of the spider. The first-instar larva hatches from the egg 2 to 3 days later. The larva only partially emerges from the egg chorion, because the egg is the only structure that enables it to stay attached to its host. As a first instar, the larva creates large holes in the abdomen of the spider to access the spider's hemolymph, which dries to form a type of “saddle”. Researchers believe that the larva may add a chemical to the hemolymph that slows its coagulation. The first-instar larva also feeds on the hemolymph of the host.
After another 2 to 3 days, the larva molts into the second-instar stage. As a second instar, the larva can insert a pair of hook-like structures into the "saddle" to hold itself in place on the host, outside of the egg chorion. Almost the entire body of the larva becomes visible as it emerges further from the egg chorion. This instar stage lasts less than a day, as the larva soon kills the host and pupates.
The exact number of instars in H. argyraphaga is unknown. During the final instar stage of the wasp, the wasp chemically induces the host spider into spinning a special "cocoon web" that is designed to hold and protect the cocoon of H. argyraphaga. The web design results from the repression of all subroutines of normal web construction except one, which is continuously repeated when the spider builds the web. Once it completes this task, the spider becomes paralyzed and dies. The larva feeds on any remaining hemolymph in the spider corpse, and then it dislodges from the abdomen of the spider. The larva weaves its cocoon while hanging from the web. The special cocoon web is strong and can support and protect the cocoon of H. argyraphaga.
To optimize the chances of encountering female wasps, Hymenoepimecis argyraphaga males fly in seemingly random patterns but typically drift above the leaves of undergrowth plants. This mate search pattern tends not to bring them into contact with the females that have recently emerged from their cocoons, which are typically protectively concealed deep in the vegetation of undergrowth plants.
A male encounters a female once she leaves her cocoon and lands on the leaf tips at the top of the undergrowth. No empirical evidence indicates that H. argyraphaga produces pheromones to attract males; however, the males usually locate females within minutes, suggesting that a long-range pheromone is used.
A male lands on a female and curls his abdomen forward to copulate, which usually lasts less than 10 seconds. Males vary in their ability to locate and successfully copulate with females, and they exhibit no aggressive behavior toward conspecific wasps. Females mate with one male at a time. They kill the offspring of other females if they find a larva or egg on a host they capture, and the removed offspring is replaced with their own egg. (Ayasse, et al., 2001; Eberhard, 2000b)
Hymenoepimecis argyraphaga has a haplodiploid genetic system, in which unfertilized eggs develop into males, and fertilized eggs develop into females. Environmental change or stress can affect the sex ratio of a H. argyraphaga population. Unfertilized eggs may be laid more often than fertilized eggs during certain seasons or under certain ecological conditions and vice versa.
A female wasp uses one of two methods to attack a Plesiometa argyra host. In one method, the wasp hovers above the spider web for a few seconds, quickly dips down, and puts her legs through the web to grab the spider and hold on tightly. The spider tries to fight off the attacking wasp while the wasp jabs the spider repeatedly with her ovipositor. The second method is to deceive the host. The female wasp may lay in the middle of the web, with her legs stiffened. When the spider approaches the wasp, she grabs the spider and stings it repeatedly with her ovipositor. After these short stings, the wasp inserts her ovipositor directly into the cephalothorax of the spider and stings the host for almost 2 minutes. The spider initially struggles but eventually grows still as it becomes paralyzed by the venom. Once the host is completely paralyzed, the wasp continues to stab the spider, inserting more venom. The spider host remains paralyzed for 5 to 10 minutes.
While the host is paralyzed, the wasp probes the spider's abdomen for existing larvae. This behavior allows her to insert venom into the eggs or larvae and remove them. It is uncommon for more than one egg or larva to be found on one host, because female wasps are skilled at finding and removing previously laid eggs and larvae. Experimental observations of parasitized spiders indicate that infanticide is relatively common, based on aged feeding scars in nearly half of the hosts. If two eggs happen to be laid on the same spider host, the smaller larva is extricated from the host by the larger one.
Hymenoepimecis argyraphaga females typically glue unfertilized (male) eggs to small, immature female spider hosts and sometimes mature male spiders. Females usually do not parasitize mature male hosts because mature males are less likely to weave strong cocoon webs. Strong cocoon webs benefit wasp offspring, because stronger webs more effectively protect the offspring from predators. Fertilized (female) eggs are glued to female spiders, and the wasps are more likely to lay fertilized eggs on a spider if the host is larger. (Eberhard, 2000b; Godfrey, 1994)
Dissections of Hymenoepimecis argyraphaga females have indicated that they contain massive fat bodies and uric acid, both of which decrease as the eggs in her body increase in size. These observations suggest that the females provision the eggs as they develop inside her body.
Females show preferences in their host selection, which provides their offspring with adequate resources as the larvae develop. Females prefer to lay eggs on mature female Plesiometa argyra spiders. The female wasp finds a suitable host, likely by following a chemical stimulus. After the wasp has removed any competing larvae, she glues her egg to the abdominal cuticle of the spider. After the egg is attached to the spider, the wasp offspring gets no further parental care.
The male’s role ends at copulation in this wasp species. (Eberhard, 2000b)
Larvae feed on the hemolymph of the spider host, while adults rely on sugar and nectar food sources. (Eberhard, 2000b)
Hymenoepimecis argyraphaga larvae may be more susceptible to predation than adults. The eggs and larvae of H. argyraphaga can be killed by conspecific adult females. As it pupates, Hymenoepimecis argyraphaga can be attacked by idiobiont parasitoids (chalcid wasps in the genus Conura), although it suffers relatively less mortality at this stage than other parasitoid wasp species. Other predators can remove the H. argyraphaga cocoon or its contents from the cocoon web. Sometimes predators eat the host spider, and they might also prey on the wasp. Spiders also sometimes eat H. argyraphaga adults. When attacked, the wasp defends itself chemically, releasing a foul odor. (Eberhard, 2000b)
Highly specialized parasitoids can be used as biological control to limit the population size of a pest species. However, Hymenoepimecis argyraphaga parasitizes a host spider that is not likely to grow out of control or cause any economic problems. Rather, studying the ways in which H. argyraphaga manipulates Plesiometa argyra as a host may lead to discoveries in biochemistry, physiology, ecology, and related fields. (Shaw, 2006)
Hymenoepimecis argyraphaga is not known to be harmful to humans.
The conservation status of Hymenoepimecis argyraphaga has not been evaluated.
Erin Fowler (author), Radford University, Elizabeth Wason (author, editor), Animal Diversity Web Staff.
living in the southern part of the New World. In other words, Central and South America.
living in landscapes dominated by human agriculture.
having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.
uses smells or other chemicals to communicate
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
parental care is carried out by females
union of egg and spermatozoan
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
An animal that eats mainly plants or parts of plants.
fertilization takes place within the female's body
A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.
having the capacity to move from one place to another.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
the area in which the animal is naturally found, the region in which it is endemic.
an animal that mainly eats nectar from flowers
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death
chemicals released into air or water that are detected by and responded to by other animals of the same species
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
scrub forests develop in areas that experience dry seasons.
reproduction that includes combining the genetic contribution of two individuals, a male and a female
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
uses touch to communicate
Living on the ground.
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
uses sight to communicate
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Godfrey, H. 1994. Parasitoids: Behavioral and Evolutionary Ecology. Princeton, New Jersey: Princeton University Press.
Gonzaga, M., J. Sobczak. 2007. Parasitoid-induced mortality of Araneus omnicolor (Araneae, Araneidae) by Hymenoepimecis sp. (Hymenoptera, Ichneumonidae) in southeastern Brazil. Naturwissenschaften, 94: 223-227.
Mendez, A., R. Bermudez, J. Cardona, N. Franz. 2009. "Leucauge argyra (Walckenar, 1842)" (On-line). Accessed November 13, 2011 at http://rolemodel.uprm.edu/student-outcomes/zoology/reports/Leucauge-argyra-Page-Mendez-Bermudez-Spring2009.pdf.
Shaw, M. 2006. Habitat considerations for parasitic wasps (Hymenoptera). Journal of Insect Conservation, 10: 117-127.