As with many insects, this species apparently communicates mainly by using olfaction and vision. Males are known to release a pheromone that attracts females (and other males), but attracted individuals do not approach closely to artificial sources of the pheromone, and it is presumed that they use visual attraction at close range. Although this has not been studied, the species presumably uses its antennae for olfaction (typical of insects), and probably detects potential prey item using largely scent and, at close range, vision. Typical of all stink bugs, this species has thoracic glands that produce a musty odor when handled, presumably as an anti-predator mechanism.
Communication Channels: visual ; chemical
Other Communication Modes: pheromones
Perception Channels: visual ; chemical
Stiretrus anchorago is not listed as an endangered or threatened species on any international, national, or state lists.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
Stiretrus anchorago has incomplete metamorphosis typical of true bugs (Hemiptera). The egg stage lasts 8 to 11 days, first instar 4 to 8 days, second instar 3 to 8 days, third instar 3 to 7 days, fourth instar 4 to 6 days, and the fifth instar 7 to 15 days. There is no information on the length of the adult stage. The species is presumed to be bivoltine over most of its range because of the appearance of adults twice during the season. Adults diapause over winter and start laying eggs early in the spring. The second generation starts egg-laying in late May or early June. Females lay several egg masses, with about 4 days in between each mass. The eggs are laid in a double row, with a mean of 11.4 eggs per mass. The first instar hatches and remains near the eggs without feeding. After molting to the second instar, the nymphs become predators on smaller insects and this continues through the adult stage. Nymphs stop feeding for about 2 days before each molt.
This species has 14 chromosome pairs, which is the most common number for species in their order (Pentatomidae). Males have XY chromosomes, while females have XX chromosomes.
Development - Life Cycle: metamorphosis ; diapause
There is no indication that this species has a negative impact on humans. People may occasionally experience the musty odor emitted from the "stink" glands, but this causes no real discomfort.
There may be some benefit that this species provides in agricultural fields, at least in southern parts of the United States. It has been noted as a predator in both soybean and alfalfa fields and is known to consume major herbivores on these crops. No controlled studies have documented a significant positive effect on production.
Positive Impacts: controls pest population
This species is one of many fairly generalist insect predators that feed by using sucking mouthparts to take in nutrients from a prey item. It may have an impact in some agricultural settings, where it can be fairly common. It is most likely to have an impact on the specific beetle, moth, or butterfly populations that it utilizes as its main food sources, but it was only a minor source of mortality in one detailed study of survivorship in the Baltimore checkerspot butterfly (Euphydryas phaeton). It also serves as a host for tachinid flies (Cylindromyia fumipennis). The tachinid fly was reared from adults twice, with the larvae emerging from the adult bug, forming its pupa, and emerging about 10 days later.
Commensal/Parasitic Species:
First instars of this species do not feed, but evidently need a source of water for survival. Stiretrus anchorago is a predator from the second instar through adulthood. It is known to be an insectivore, feeding on the larvae of Lepidoptera and Coleoptera. It consumes larvae by stabbing them with its beak (rostrum), secreting digestive enzymes, and then sucking back the digested contents. In the Lepidoptera, it has been found feeding on black swallowtails (Papilio polyxenes), sleepy oranges (Eurema nicippe), Baltimore checkerspots (Euphydryas phaeton), soybean loopers (Pseudoplusia includens), cabbage loopers (Trichoplusia ni), gypsy moths (Lymantria dispar), and tent caterpillars (Malacosoma americanum). Among beetles (Coleoptera), it has been recorded feeding on the larvae of alfafa weevils (Hypera postica), Mexican bean beetles (Epilachna varivestis), squash beetles (Epilachna borealis), Colorado potato beetles (Leptinotarsa decemlineata), sumac flea beetles (Blepharida rhois), green tortise beetles (Nuzonia pallidula), ragweed leaf beetles (Zygogramma suturalis), leaf beetles (Zygogramma heterothecae), spotted asparagus beetles (Crioceris asparagi), cottonwood leaf beetles (Chrysomela scripta), and elm leaf beetles (Xanthogaleruca luteola). At least one species of tortoise beetle (Hemisphaerota cyanea) uses long strands of frass to protect itself from some predators, and Stiretrus anchorago is deterred by this defense, so not all Chrysomelidae are used as prey.
Observations of adults probing the flowers of goldenrod may indicate some nectar feeding, but this has not been confirmed.
Animal Foods: insects
Primary Diet: carnivore (Insectivore )
Stiretrus anchorago occurs in the Nearctic Region from New England and Ontario south to Florida and Mexico. Its range extends as far west as Iowa, Kansas, and Texas. It has also been reported from California.
Biogeographic Regions: nearctic (Native )
Stiretrus anchorago can be found primarily in open areas, including waste areas, old fields and agricultural fields, where it often feeds on pest herbivores. It also occurs along the margins of hammocks and swales in Florida.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: savanna or grassland
Wetlands: marsh
Other Habitat Features: suburban ; agricultural ; riparian
Individuals of Stiretrus anchorago live no more than a few weeks to months. Under captive rearing the egg stage lasts 8 to 11 days, first instar 4 to 8 days, second instar 3 to 8 days, third instar 3 to 7 days, fourth instar 4 to 6 days, and fifth instar 7 to 15 days. No data are available on the length of adult life in this species, but adults have been reported from throughout the summer, indicating an overlap of the generations, and an indication that individuals live at least a few weeks as adults. The last generation of the year overwinters as adults, and thus has a longer adult lifespan, although mostly inactive.
Adult: Stiretrus anchorago is a striking species of stink bug with quite variable coloration. The color ranges from solid steel blue (form violaceus) to blue-black with red, orange and cream markings on the pronotum, scutellum, and sides of abdomen (form anchorago - mainly northern), to reddish brown with mainly yellow markings (form fimbriatus - mainly southern). Other color variants are known, including form personatus, with a red pronotum, a wide, blue-black median stripe extending from the front of the pronotum to the tip of the scutellum, and two spots on each side of the pronotum. The species is easily distinguished by the scutellum, which is unusually large and U-shaped, nearly reaching the end of the abdomen, and resembling a shield bug (Scutelleridae).
Eggs: The eggs are darkly pigmented, nearly black, from 1.24 to 1.35 mm in length (mean = 1.30 mm) and 0.86 to 1.13 mm in diameter (mean = 1.03 mm). Their upright shape is oval, being widest at the middle. They have serrated ridges in a reticulated pattern.
First Instar: The earliest instar is 1.24 to 1.35 mm (mean 1.31 mm) long and 1.27 to 1.30 mm (mean 1.28 mm) wide. It is round or oval and widest at the third or fourth abdominal segment. The dorsal surface is mainly fuscous, with a reddish-orange median marking and reddish-orange eyes. The ventral surface is reddish-orange. The legs are fuscous. The antennae are four-segmented, about 1.10 mm long and lighter colored than the head.
Second instar: The second instar is 2.27 to 2.43 mm (mean 2.37 mm) long and 2.19 to 2.30 mm (mean 2.23 mm) wide. The shape is similar to the first instar. The entire dorsal surface is black, and the eyes are bright red. The ventral surface is mainly reddish-orange. The legs are pale yellow, except for the coxae, the proximal half of the femora, and distal half of the second tarsus, which are all fuscous. The antennae are 1.84 mm long. The first and last segments are fuscous, and the middle two are pale.
Third instar: This stage is 3.46 to 3.89 mm long (mean 3.73 mm) and 3.24 to 3.29 mm wide (mean 3.26 mm). The coloration is very similar to the second instar, but the legs are entirely pale except the distal third of the second tarsus, and the basal segment of the antenna is pale. The antennal length is 2.49 mm.
Fourth instar: The fourth instar is 4.75 o t5.35 mm long (mean 5.00 mm) and 4.21 to 4.64 mm wide (mean 4.44 mm). The coloration is basically identical to the third instar, but the forewing pads extend to the caudal edge of the metatergum. The antennal length is 3.37 mm.
Fifth instar: The final nymphal instar is 6.48 to 8.32 mm long (mean 7.16 mm) and 5.29 to 5.89 mm wide (mean 5.58 mm). The head coloration is similar to the third and fourth instars, with the antennal length 4.39 mm. The thorax is mainly black dorsally, with a yellow, triangular, median mark on the mesothorax, and sometimes with yellowish lateral spots on the pro- and mesothorax. The forewing pads extend to the middle of the third abdominal segment, with the hindwing pads visible between them. The legs are similar to the fourth instar. The dorsal abdomen is still black, but the ventral surface is yellow-orange, with five median spots.
Range length: 7 to 11.5 mm.
Other Physical Features: ectothermic ; bilateral symmetry ; polymorphic
Sexual Dimorphism: female larger
Typical of all stink bugs, this species has thoracic glands that produce a musty odor when handled, presumably as an anti-predator mechanism. No predators have been recorded.
Known Predators:
Anti-predator Adaptations: aposematic
Stiretrus anchorago has two generations per year over most of its range. Both males and females will have multiple matings with different individuals. Individuals are otherwise solitary.
Recently, it has been determined that males have a pheromone-producing structure on the underside of the abdomen. This consists of a set of velvety patches of darker color. These patches emit 6,10,13-trimethyl-1-tetradecanol, with a small amount of other components. This compound has been shown to attract both males and females in the field, but they rarely approach closely to the source. Evidently there are other important cues need for the final attraction, possibly visible cues.
Mating System: polygynandrous (promiscuous)
Adults breed and lay eggs continuously while alive. Females lay a mean of 11.4 eggs per mass, with at least one female recorded laying 6 masses, for a total of about 68 to 70 eggs per female. Although generations may overlap, there are two generations per year, with the first generation reproducing from early spring through May and the second generation reproducing from late May or early June through fall. Immatures are independent, the only adult contribution being nutrients in the egg. Reproduction is only known to be sexual, with internal fertilization of ova.
Breeding interval: Individuals breed continuously as adults, with adults occurring early in the season through about June and starting again in early August. Females lay eggs about every 4 days during the mating season.
Breeding season: Adults mate continuously while alive, from early in season to about June, and then from early August into the fall.
Average eggs per season: about 68-70.
Range gestation period: 8 to 11 days.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous
There is essentially no parental investment in this species, except nutrients deposited in eggs.
Parental Investment: pre-hatching/birth (Provisioning: Female)
Stiretrus anchorago, commonly known as the anchor stink bug, is a species of predatory stink bug in the family Pentatomidae.[1][2][3][4] It is found in Central America and North America.[1] It is known to prey upon Epilachna varivestis and Hypera postica. [5][6]
These five subspecies belong to the species Stiretrus anchorago:
Data sources: i = ITIS,[1] c = Catalogue of Life,[2] g = GBIF,[3] b = Bugguide.net[4]
Stiretrus anchorago, commonly known as the anchor stink bug, is a species of predatory stink bug in the family Pentatomidae. It is found in Central America and North America. It is known to prey upon Epilachna varivestis and Hypera postica.
