The genus Calliphora contains the familiar bluebottle flies, which are easily recognised by their:
- large size
- dark blue, almost black colour
- broad compact body
- metallic abdomen with silvery dusting
- The first antennal segment (flagellomere) is noticeably large.
- The back of the head (occiput) has pale hairs. Parts of the head and antennae have a reddish ground colour
- Legs are bristly.
- Males have only a very narrow gap between the eyes, females a broad gap.
- Both calypteras brown or at the very least conspicuously pigmented; upper calyptera with dark rim and dark hairs along rim.
- Basicosta yellow or yellowish-brown, never all black.
- Anterior thoracic spiracle orange.
- Frons, upper half of parafacialia, most of face, posterior third of jowls and occiput with dark ground colour.
- Facial ridges, mouth-edge, and anterior two-thirds of jowls with orange ground colour.
- Occiput mostly with pale hairs.
Calliphora vicina is the most common and widespread bluebottle blowfly in the UK, spatially and seasonally, and is the species most likely to be encountered.Also common is the rural bluebottle Calliphora vomitoria, which can be easily distinguished from C. vicina by the conspicuous covering of orange hairs on the occiput.One leading authority on this group has reported that vicina is often confused with uralensis in entomological collections. However, C. uralensis has a dark basicosta, and the anterior thoracic spiracle is also dark.
In Britain, carrion blowflies go through several generations per year, and the breeding season is only restricted by temperature. Males attempt to mate repeatedly, but females may only mate once, shortly after emerging as adults.Once mated, females store the sperm they receive in 3 special organs called the spermathecae and they will repulse further mating attempts for as long as the store lasts. Females require a protein meal to mature an egg batch, and must find a suitable food source to deposit eggs on once they are mature.
Larvae hatch from eggs laid by females. There are 3 larval stages or instars:
- The 1st and 2nd instars are of very short duration.
- Most of the growth takes place during the final, 3rd instar.
Very little is known about the dispersal mechanisms for Calliphora vicina, although bluebottles are certainly capable of prolonged flight and can cover considerable distances.No data is available on distances covered by Calliphora species, but studies that used carcasses to attract flies recovered marked Lucilia individuals as much as 6.5km away from their release point.
- Calliphora vicina flies are generally large, 5-13mm in length.
- Their considerable size range is an adaptation to relying on carrion as a larval food source. The level of competition can be extremely high, and the food source only lasts a short time.
- Within limits, maggots receiving only limited nutrition before the food runs out are able to mature into miniature adults.
The growth rate of C. vicina has been studied in great depth because of the forensic importance of this species throughout temperate Europe. As poikilotherms, temperature has the biggest effect on their rate of growth. Records in the literature give the time needed to develop from egg to adult emergence as 18-24 days at 27oC, compared with 31-35 days at 15oC.Temperature also affects final adult size, with smaller adults emerging from cultures reared at high temperatures. Temperatures above 30oC appear to be lethal to C. vicina.The quality and quantity of the available food also affect growth. Final adult size has a profound effect on the fly's:
Little is known of the life span of British blowflies in the wild. It is thought that the majority of C. vicina females only survive to lay one batch of eggs, which would give them a life span of 1 to 2 months.
- In the south of the UK a small population of flies will over-winter as adults, surviving for 6 months or more.
- In the north, the population over-winters as post-feeding larvae in a state of arrested development known as diapause. The trigger for this is declining day length and low temperatures, and it is broken in the spring when temperatures increase.
Regularity: Regularly occurring
Type of Residency: Year-round
Flowering Plants Visited by Calliphora vicina in Illinois
(observations are from Robertson, Graenicher, and Mehrhoff)
Aceraceae: Acer saccharum [oozing sap] (Rb); Apiaceae: Pastinaca sativa sn (Rb); Asteraceae: Antennaria neglecta [unsp sn/fp] (Gr), Aster lanceolatus sn/fp (Gr), Aster lateriflorus sn/fp (Gr), Aster novae-angliae sn/fp (Gr), Aster puniceus sn/fp (Gr), Erigeron philadelphicus sn/fp (Gr), Euthamia graminifolia sn/fp (Gr); Caprifoliaceae: Symphoricarpos occidentalis sn/fp (Gr); Cornaceae: Cornus obliqua sn (Rb); Orchidaceae: Isotria verticillata exp np (Mhr); Portulacaceae: Claytonia virginica sn (Rb); Ranunculaceae: Clematis virginiana [stam sn] (Rb); Rosaceae: Crataegus intricata sn (Rb), Crataegus mollis sn (Rb), Prunus americana sn (Rb), Prunus serotina [flwr sn] (Rb); Salicaceae: Salix discolor [unsp sn/fp] (Gr), Salix rigida [pist sn] (Rb); Santalaceae: Comandra umbellata sn fq (Rb); Smilacaceae: Smilax ecirrhata sn/fp (Gr); Tiliaceae: Tilia americana sn (Rb)
- the chalcid Nasonia vitripennis - the larvae are external parasites of blowfly pupae within the puparium, and can cause high mortalities in blowfly populations.
- the braconid Alysia manducator - the larvae are internal parasites of the pupae.
Blowflies have a wide range of natural predators. The maggots are probably subjected to the heaviest predation. Their chosen food, carrion, is itself an attractive food source for many animals, and maggots occur in high concentrations on carcasses. In the UK, their main predators are beetles, particularly species of the genera Carabus and Hister. Vertebrate predators include:
- birds such as crows and choughs
In 1957, MacLeod and Donnelly estimated the local population density of C. vicina in an area near Carlisle to be:
- 50 to 200 flies per acre in August
- 400 to 1000 in September
- 700 to 1000 in October
Calliphora vicina is considered to be highly synanthropic in most parts of its range. Overall numbers have probably increased over recent centuries in association with human populations.
Existing management practices are aimed at killing or excluding blowflies (for example, by fly screening) so that they, and others with similar feeding habits, don't impact on food hygiene standards.
Calliphora vicina is widely distributed throughout the Holarctic region. A frequently synanthropic species, it is also an invasive species and has already followed humans into:
- South America
- The Afrotropical region
- Northern India
- New Zealand
C. vicina is a cosmopolitan species found from the lowlands to above the treeline.In Europe it is a very common urban species closely associated with humans.
Blowflies are not the only organisms to feed on carrion and there are a number of other invertebrates, bacteria and fungi that will colonise a corpse. However, in more temperate regions where the action of vertebrate scavengers is less important, blowflies are considered the primary agents of decomposition. They play a central role in the carbon cycle, taking the carbon and other nutrients in the carrion back down the food-chain.
Life History and Behavior
Little is known about the large-scale migrations of blowflies. Calliphora vicina adults have been recorded moving southwards in autumn in a UK study, suggesting the species may be migratory in at least part of its range.
C. vicina has been recorded from cases of myiasis, a parasitic disease condition where fly larvae are found feeding on the tissues of living mammals, including humans. Such cases are not thought to be very common and are:
- generally only reported from small mammals, such as mice and hedgehogs
- occasionally reported from reptiles such as tortoises (Sales et al., 2003)
Evolution and Systematics
Exoskeleton of insects detects strain and load change via campaniform sensilla.
"In insects, the campaniform sensillum is a hole extending through the cuticle arranged such that its shape changes in response to loads. The shape change is rotated through 90° by the suspension of a bell-shaped cap whose deflection is detected by a cell beneath the cuticle. It can be sensitive to displacements of the order of 1 nm. The essential morphology [is] a hole formed in a plate of fibrous composite material." (Vincent et al. 2007:63)
"A campaniform sensillum (figure 1) is a kind of strain sensor found in insects, e.g. the blowfly (Calliphora vicina). The campaniform sensillum is basically an opening in the cuticle (with a size of 5–10 μm in diameter for the circular shape one) covered by membrane layers. The shape of the opening is generally ellipse and sometimes almost circular. Deformation in the insect’s cuticular layer is sensed by the campaniform sensillum using mechanical coupling, transduction and an encoding mechanism to transfer the environmental information to the insect’s nervous system. Previous work by one of the authors (JFVV) showed that the mechanical coupling mechanism was resolved into discrete components: a cap surrounded by a collar, a joint membrane and an annulus-shaped socket septum with a spongy compliant zone (the spongy cuticle). The coupling mechanism is a mechanical linkage which transforms the stimulus into two deformations in different directions: monoaxial transverse compression of the dendritic tip of a sensory neuron cell, which acts as a transducer, and vertical displacement of the cap. The natural campaniform sensilla, regardless of the high Young modulus of the exocuticle layer of the insect (k ≈ 109 Nm−2), can still detect changes. These sensors are as sensitive to displacement in that stiff structure as the receptors in the human ear are to sound . This sensitivity is among others due to their unique membrane-in-recess microstructure. The membrane located inside a blind hole amplifies the strain." (Wicaksono et al. 2005:S72)
Learn more about this functional adaptation.
Fluid secreted from tiny hairs on the feet of the European blowfly help it stick to surfaces via capillary action adhesion.
"A study of fly footprints shows that the offending insect relies mainly on capillary forces generated by fluid secreted from its feet. Mattias Langer et al. used atomic-force microscopy to examine the adhesiveness of tiny puddles of foot fluid left by a fly, Calliphora vicina, as it walked across a glass slide. As the fluid evaporates, its stickiness decreases, showing that the fluid plays an important role in generating adhesion between foot and substrate. Adhesion measured in air was much stronger than that measured in an aqueous environment, indicating that capillary forces are mainly involved in the fly's attachment mechanism." (Hopkin 2004:756)
"The attachment pads of fly legs are covered with setae, each ending in small terminal plates coated with secretory fluid. A cluster of these terminal plates contacting a substrate surface generates strong attractive forces that hold the insect on smooth surfaces. Previous research assumed that cohesive forces and molecular adhesion were involved in the fly attachment mechanism. The main elements that contribute to the overall attachment force, however, remained unknown. Multiple local force-volume measurements were performed on individual terminal plates by using atomic force microscopy. It was shown that the geometry of a single terminal plate had a higher border and considerably lower centre. Local adhesion was approximately twice as strong in the centre of the plate as on its border. Adhesion of fly footprints on a glass surface, recorded within 20 min after preparation, was similar to adhesion in the centre of a single attachment pad. Adhesion strongly decreased with decreasing volume of footprint fluid, indicating that the layer of pad secretion covering the terminal plates is crucial for the generation of a strong attractive force. Our data provide the first direct evidence that, in addition to Van der Waals and Coulomb forces, attractive capillary forces, mediated by pad secretion, are a critical factor in the fly's attachment mechanism." (Langer et al. 2004:2209)
Learn more about this functional adaptation.
Molecular Biology and Genetics
Barcode data: Calliphora vicina
Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Download FASTA File
Statistics of barcoding coverage: Calliphora vicina
Public Records: 50
Specimens with Barcodes: 57
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: NNR - Unranked
Relevance to Humans and Ecosystems
Calliphora vicina is a member of the family Calliphoridae, which includes blow flies and bottle flies. These flies are important in the field of forensic entomology. C. vicina is currently one of the most entomologically important fly species because of its consistent time of arrival and colonization of the body following death.
C. vicina is known as a blue bottle fly because of the metallic blue-gray coloration of its thorax and abdomen. It is distinguished from the commonly known C. vomitoria by its bright orange cheeks. The blue bottle fly is approximately 10–11 mm in length. The sclerites at the base of the coxa are yellow or orange. By chaetotaxy, the study of bristle arrangement, Calliphorids are characterized by having black bristles on the meron and two to three bristles on the notopleuron.
The similarities between the different species of Calliphora can make identification of immature stages nearly impossible. From the first instar to the pupa stage C. vicina is identical to that of C. vomitoria.
C. vicina goes through five generations in a year at a threshold temperature of 27˚ C (81˚ F). A female C. vicina can lay up to 300 eggs, on fresh carrion or on open wounds. The larvae go through three instar stages. The first instar hatches in approximately 24 hours after the eggs are laid. It goes through its second instar in 20 hours and its third instar in 48 hours. Under favorable conditions, the larvae feed for about three to four days. When the larvae complete their development, they disperse to find an adequate place to pupate. The C. vicina pupa stage last about 11 days. At 27˚ C, C. vicina’s life cycle lasts approximately 18 days.
Climatic factors, such as temperature, are known to influence egg-laying and development of instar-larvae. In warmer weather the life cycle can last a little less, and in cooler temperatures the life cycle takes a little longer. Knowing the duration between the three instars and pupa stage and post-feeding larval dispersal can be useful to determine the post mortem interval in a criminal case.
C. vicina are found throughout the U.S. in urban areas and are most abundant in early spring and fall where the temperatures are around 55-75˚F (13-24˚C). The species predominates in Europe and the New World, but has found its way into other countries via harbors and airports. It was first recorded in South Africa in 1965 when a specimen was collected near Johannesburg, but specimen collections have been few and sporadic since then.
Post mortem interval estimation
One of the key characteristics of using blow flies in developing a post mortem interval estimate is the succession of insects that colonize the body. Based on the insects present at the time, a reasonable time frame for death may be established. C. vicina has its own part in the succession of the corpse.
C. vicina plays a major role in corpse colonization during the winter months, with less of a presence during the warmer months when temperature is less of a constraint. This fly has a lower threshold temperature for flight activity than other blow-flies, allowing for greater prevalence during colder periods. This period of activity must be considered when evaluating the presence or absence of this fly.
When using the age of maggots to determine the PMI, the time before arrival is an important factor. The succession of C. vicina involves the arrival of adults two days after death. Therefore, two days must be added to the maximum age determined for flies found on the body.
C. vicina play an integral part in post mortem interval determination. Factors such as region, weather temperatures, time of day and conditions under which the body was found all contribute to determining a post mortem interval (PMI). To complete the calculation the entomologist must consider what is commonly known about C. vicina and integrate it with experimental data gathered from a crime scene. The entomologist must know how the blow-fly behaves specifically in the area where the body was discovered. This involves recording environment temperatures at the crime scene as well as retrieving a history of the climate in the region. C. vicina in particular is adapted to cooler temperatures, appearing most commonly in winter and less often in the summer months. This puts their flight activity threshold at above 55-60 °F (13-16 °C), a lower temperature than most other blow-flies. Knowing the threshold temperature allows the entomologist to calculate accumulated degree days, which in turn helps determine PMI.
Some knowledge regarding C. vicina behavior is well known. Case studies have shown that it is not the first species in arrival. However, it does appear one to two days before Phaenicia sericata. However, determining PMI is an intricate process because there is still much that we do not know about C. vicina behavior. For instance, it is a long held belief that the species is not nocturnally active. Recently, however, it has been shown that C. vicina is indeed active at night under certain experimental conditions.
As C. vicina continues to be researched, more information about the behavior will be gained to allow for a more complete picture of the lifecycle, thereby leading to better estimates of time of colonization. New knowledge, such as the activity of C. vicina at night, will provide forensic entomologists with a better tool for their PMI estimation development.
- Simpson DP (1979). Cassell's Latin Dictionary (5 ed.). London: Cassell Ltd. p. 883. ISBN 0-304-52257-0.
- BCSO Identification - Entomology - Blowfly Life Cycle
- Gomes, L; Godoy WAC; Zuben CJV (2006). "A Review of Postfeeding Larval Disposal: implications for forensic entomology". Naturwissenschaften 93 (5): 207–215. doi:10.1007/s00114-006-0082-5. PMID 16538375.
- Case Studies in Forensic Entomology
- Williams KA, Villet MH. A new and earlier record of Chrysomya megacephala in South Africa, with notes on another exotic species, Calliphora vicina (Diptera: Calliphoridae.) African Invertebrates. 2006 Dec;47:347-50.
- Catts P, Haskell N, Entomology & Death: A Procedural Guide, Joyce's Print Shop, Inc., 1990.
- Arnaldos MI, García MD, Romera E, Presa JJ, Luna A. Estimation of postmortem interval in real cases based on experimentally obtained entomological evidence. Forensic Sci Int. 2005 Apr 20;149(1):57-65.
- Lang MD, Allen GR, Horton BJ. Blowfly succession from possum (Trichosurus vulpecula) carrion in a sheep-farming zone. Med Vet Entomol. 2006 Dec;20(4):445-52.
- Battan Horenstein M, Linhares AX, Rosso B, García MD. Species composition and seasonal succession of saprophagous calliphorids in a rural area of Córdoba: Argentina. Biol Res. 2007;40(2):163-71. Epub 2007 Nov 21
- Gennard D, Forensic Entomology: An Introduction, Wiley, John & Sons, Incorporated, 2007.
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