Calliphora vicina

Calliphora vicina
Calliphora vicina
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Diptera
Suborder:	Brachycera
Infraorder:	Muscomorpha
Subsection:	Calyptratae
Superfamily:	Oestroidea
Family:	Calliphoridae
Genus:	Calliphora
Species:	vicina

Calliphora vicina is a member of the family Calliphoridae, also known as the blow-flies. These flies are important in the field of forensic entomology.

Biology

Calliphora vicina is commonly 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 buy its bright orange cheeks. The blue bottle fly is approximately 10-11 mm in length. The sclerite at the base of the coxa are yellow or orange. By chaetotaxy, Calliphorids are characterized by having black bristles on the meron and 2-3 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.

Lifecycle

Calliphora vicina goes through 5 generations in a year at a threshold temperature of 27 degrees Celsius. A female Calliphora 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 3-4 days. When the larvae complete their development, they disperse to find an adequate place to pupate. The Calliphora vicina pupa stage last about 11 days. At 27 degrees Celsius, Calliphora vicina’s life cycle last 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.

Distribution

The Calliphora 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 Fahrenheit.

Behavior

Calliphora 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 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 found. 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, a lower temperatures than most other blow flies [3]. 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 first in arrival, but rather appears 1 to 2 days before Phaenicia sericata [4]. 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.

Post mortem interval estimation

One of the key characteristics of using blow flies in developing a post mortem interval (PMI) 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. Calliphora vicina has its own part in the succession of the corpse.

Calliphora 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 blowflies, 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 Calliphora 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.

Conclusion

Calliphora vicina is currently one of the most entomologically important fly species because of its consistent time of arrival. New strategies for determining PMI and better ways of interpreting entomological evidence from crime scene continue to be developed. The better entomologists understand the behavior patterns of C. vicina the more accurately they can determine pertinent information about a homicide.