Lucilia thatuna

Lucilia thatuna belongs to the family Calliphoridae, the species most commonly referred to as the blowflies, and the genus Lucilia. Along with several other species of Lucilia, L. thatuna is commonly referred to as the green bottle fly. L. thatuna is very scarce and not much is known about this particular fly. It has been noted to reside in mountainous regions of the northwestern United States.

Taxonomy and history

The Lucilia genus was first identified in 1830 by Jean-Baptiste Robineau-Desvoidy, a French entomologist and physician. In 1926, American entomologist Julie Bockman identified the species Lucilia thatuna during his work with the U.S. Bureau of Entomology. The species was also referred to as Bufolucilia thatuna and Phaenicia thatuna until 1991 when Knut Rognes synonymized these genera names with Lucilia. This species can be identified through the Keys to the Genera and Species of Blowflies (Diptera: Calliphoridae) of America North of Mexico (Whitworth 2006).

Morphology

Although other species in the Lucilia genus are called "green bottle flies," L. thatuna can be identified by a shiny, bluish thorax and abdomen (Whitworth 2006). The mature adult, also known as an imago, generally ranges from 4.5 to 10 mm in length (Byrd 2001). Size is strongly correlated with the availability of nutrient rich food and environmental conditions (Florin 2001).

Adult females tend to be slightly larger than males, with smaller eyes placed more laterally on the head and the ocellar triangle not surpassing the halfway point to the lunule. The narrow frons on the male distinguishes it from other common species such as Lucilia cuprina and Lucilia sericata. Other distinguishing characteristics include the presence of three postacrostichal setae and the first flaellomere broader in width than the parafacial at the level of the lunule (Whitworth 2006).

Life cycle and development

Once an adult female has fully developed eggs in her ovaries, she will follow the scent of decay to suitable carrion on which to deposit her eggs. It is theorized that females will feed on the protein secreted from the carrion before depositing a possible 200 eggs through her ovipositor onto carrion. Depending on temperature, the eggs will usually hatch within a day producing the first instar larvae. These larvae will feed continuously upon the decomposing carcass until they are large enough to molt and enter the second instar. This process is repeated again for the third and final instar after which, the larva leaves the corpse to pupate. During this time, L. thatuna actively rearranges its physical composition to emerge as an adult fly after approximately two weeks depending on temperature (Byrd 2001).

Location

L. thatuna is not found in a wide variety of human habitats. Specimen collections have been few and sporadic over a ten-year period. Identification has only been documented in the United States, mainly in northwestern Idaho, Oregon, Montana, California, and Colorado. L. thatuna appears to have a local distribution in mountainous areas of elevation from 4,000 to 5,000 feet. Six specimens have been located on Mt. Moscow, two specimens on Lake Waha, three specimens in Latah County, and two specimens on Craig Mountain, Nez Perce County; all found in Idaho (Hall 1948).

Medical importance

Myiasis

As part of the family Calliphoridae L. thatuna is involved in myiasis, as most other blowflies are. Myiasis is the infestation of live or necrotic tissue on a vertebrate host by fly larvae (Stevens 2003). This disease is initiated by dipterous eggs being laid in natural body openings or exposed wounds (Stevens 2003). As can be imagined, the condition produces a variety of problems depending on the location of the larvae. L. thatuna is described as a facultative ectoparasite; it is able to live as a sacrophage or initiate myiasis. Myiasis caused by a facultative ectoparasite is semispecific (Stevens 2003). Semispecific is synonymous to facultative parasite. These flies do not utilize living organisms to lay their eggs. Rather, they will use dead organic matter; however, when a wound is present the flies will lay their eggs in it, causing myiasis.

Surgical maggots

The genus Lucilia is commonly used in maggot therapy. Maggot therapy is the process of using fly larvae to treat infected wounds; it is also known as Maggot Debridement Therapy. The maggots that are used are mass-produced and disinfected. They are placed into open wounds healing on their own. This type of therapy is effective because the maggots only eat the necrotic tissue, thus cleaning out the wound and promoting healing. The larvae used in therapy use secretions to increase efficacy of their healing properties. They usually produce positive results via three mechanisms of action: Debridement, disinfection, and stimulation of healing properties (The Role of Maggots 2009).

Forensic importance

L. thatuna is of forensic importance because it belongs to the family Calliphoridae which are more commonly known as blowflies. The Lucilia genus is overwhelmingly the first to appear on carrion if left exposed to the elements such as in an outside environment or where the carrion is accessible to insects. Upon reaching the carrion, females will oviposit their eggs in moist openings such as the eyes, nose, mouth, and anus. The reason for this is because the maggots do not regularly burrow through skin and need a soft place to begin feeding. Given an ambient temperature, forensic entomologists can use degree day calculations to produce an accurate PMI, or post mortem interval. PMIs are sometimes referred to as 'time of colonization.' Lucillia thatuna is not as well known as some of the other species, but is comparable in life cycle and forensic importance to that of Lucilia cuprina.

Current research

The most current research, from 1996, revolves around the evolutionary origin of the Lucilia genus regarding their parasitism nature. This was analyzed using mitochondrial DNA and parsimony analyses by construction of phylogenetic trees. These tests were used to consider the relationships between the numerous species within the Lucilia genus and when each species developed a myiasis habit. Although results of the conducted research show timelines of myiasis development within several of the Lucilia species, there was no clear distinction for L. thatuna developing its parasitism behavior (Stevens 1997). This has left the door open for entomologists to carry on this study and determine where L. thatuna lies in the phylogenetic history of parasitism in the genus Lucilia.

There is no documentation of any further research on this species.

Perhaps one day additional information will be discovered that will shed more light on this particular species. This may open doors that expand the forensics field or medical field. There may even be a resource that studies the relationship between L. thatuna and any human interaction that might exist. Until then L. thatuna will remain more of a mystery and lesser-known fly in the field of entomology.

References

• Bland, R. G., and H. E. Jacques. How to Know the Insects. 3rd ed. Dubuque: Wm. C. Brown Co., 1978.
• Borror, D. J., C. A. Triplehorn, and N. F. Johnson. An Introduction to the Study of Insects. 6th ed. Philadelphia: Saunders College, 1989.
• Borror, D. J., and R. E. White. A Field Guide to the Insects. Boston: Houghton Mifflin Co., 1970.
• Byrd, Jason H., and James L. Castner (Eds.). 2001. Forensic Entomology: The Utility of Arthropods in Legal Investigations. CRC. 440 p. ISBN 0-8493-8120-7
• Daly, H. V., J. T. Doyen, and A. H. Purcell III. Introduction to Insect Biology and Diversity. 2nd ed. Oxford: Oxford UP, 1998.
• Florin, Ann-Britt. Bottlenecks and Blowflies Speciation, Reproduction and Morphological Variation in Lucilia. Diss. ACTA Universitatis Upsaliensis, 2001. Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 660.
• Hall, David G. The Blowflies of North America. Vol. 4. Lafayette, IN: The Thomas Say Foundation, 1948.
• Kettle, D. S. Medical and veterinary entomology. Illustrated ed. London: Croom Helm, 1984.
• Stevens, Jamie, and Richard Wall. "The Evolution of Ectoparasitism in the Genus Lucilia (Diptera: Calliphoridae)." International Journal for Parasitology 27 (1997): 51–59. Scribd. Oct. 2008. 21 Mar. 2009 <http://www.scribd.com/doc/7111789/evolucao-lucilia>.
• Stevens, Jamie R. "The evolution of myiasis." International Journal of Parasitology 33 (2003): 1105–113.
• The Role of Maggots in Modern Wound Therapy, http://www.telfordpct.nhs.uk/healthcare_professionals/nursing_services/maggots.pdf, retrieved on 2007–05–06
• Whitworth, Terry (July 2006). "Keys to the Genera and Species of blow Flies (Diptera: Calliphoridae) of America North of Mexico". Proceedings of the Entomological Society of Washington 108 (3): pp. 718–721.