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Neotropical Entomology

Print version ISSN 1519-566XOn-line version ISSN 1678-8052

Neotrop. entomol. vol.36 no.6 Londrina Nov./Dec. 2007 



First record of Megaselia scalaris (Loew) (Diptera: Phoridae) infesting laboratory colonies of Triatoma brasiliensis Neiva (Hemiptera: Reduviidae)


Primeiro registro de Megaselia scalaris (Loew) (Diptera: Phoridae) infestando colônias de Triatoma brasiliensis Neiva (Hemiptera: Reduviidae) em laboratório



Jane CostaI; Carlos E. AlmeidaI, II; Gleidson M. EsperançaI, III; Nínive MoralesI, II; Jacenir R. dos S. MalletIV; Teresa C.M. GonçalvesIV; Angelo P. do PradoV

ILab. da Coleção Entomológica, Depto. Entomologia
IIBolsista do CNPq;
Bolsista Tec-Tec, Fiocruz/Faperj
IVNúcleo de Ultraestrutura, Lab. Transmissores de Leishmanioses. Instituto Oswaldo Cruz, Fiocruz, Av. Brasil 4365, C. postal 926, 21045-900, Manguinhos, RJ
VDepto. Parasitologia, Instituto de Biologia, Univ. Estadual de Campinas, C. postal 6111, 13083-970, Campinas, SP




Megaselia scalaris (Loew) is a cosmopolitan and synanthropic scuttle fly, eclectic in its feeding habits and acts as detritivore, parasite, facultative parasite, and parasitoid. Here we report for the first time M. scalaris infesting laboratory colonies of Triatoma brasiliensis Neiva, the most important Chagas disease vector in semiarid areas of Brazil. M. scalaris larvae were found feeding inside bugs; pupae were found in the esophagus and intestinal regions of T. brasiliensis through dissection. Other relevant information about this finding is also described in this note, including some preventive measures to avoid laboratory colonies infestations.

Key words: Phorid, infestation, triatomine


Megaselia scalaris (Loew) é uma mosca cosmopolita, sinantrópica e eclética quanto aos seus hábitos alimentares, tendo sido descrita como detritívora, parasita, parasita facultativa e parasitóide. Nesta nota, registra-se pela primeira vez, M. scalaris infestando colônias de laboratório de Triatoma brasiliensis Neiva, o mais importante vetor da doença de Chagas no semi-árido brasileiro. Larvas de M. scalaris foram encontradas alimentando-se dos órgãos internos dos triatomíneos; pupas foram encontradas na região intestinal e esofagiana de exemplares de T. brasiliensis dissecados. Outras informações relevantes sobre o achado são descritas nesta nota, bem como medidas preventivas para evitar infestações por M. scalaris em colônias de triatomíneos.

Palavras-chave: Forídeo, infestação, triatomineo



Phorids are small flies (1-6 mm) found worldwide, which are most diverse in the tropics. They are known as "scuttle fly" because they move in rapid bursts with short pauses. The genus Megaselia includes around 1,400 species distributed in tropical and subtropical areas. Megaselia scalaris (Loew) is cosmopolitan and synanthropic. The brown spots on its humped thorax, the dark eyes, and its white eggs presenting the upper side covered by thorns are some important distinctive characteristics (Furukawa & Kaneko 1981, Brown 1996). It is capable of exploring a large variety of environments and ecological niches. It has already been recorded as a polyphagous species acting as saprophagous, sarcophagous and necrophagous. It has also been described as an important detritivore species that consumes both animal and plant material (Tumrasvin et al. 1997, Koller et al. 2003, Disney 2007).

Macieira et al. (1983) and Rocha et al. (1984) emphasized the possibility of M. scalaris to act as a parasitoid in beehive of the subfamily Meliponinae and colonies of the European honey bee, Apis mellifera L. (Hymenoptera: Apidae), respectively.

Rocha et al. (1984) found well fed cattle-tick females, known as "carrapato-do-boi" (Boophilus microplus) infested by M. scalaris. They concluded that the flies were attracted by both dead and live ticks. Later, additional records of M. scalaris acting as a parasitoid of B. microplus in Brazil were presented (Veríssimo 1995, Andreotti et al. 2003).

The occurrence of M. scalaris acting as a parasitoid of insects of agronomic importance, was reported by several authors, such as: (i) grasshoppers Zonocerus variegatus (L.) by Gregorio & Leonide (1980), (ii) pre-pupae of the butterfly Peridroma saucia (Hb.) by Ulloa & Hernandez (1981), (iii) adults of the Curculio caryae (Coleoptera: Curculionidae) by Harrison & Gardner (1991), and (iv) the beetle Macrodactylus marinus (Coleoptera: Scarabaeidae) by Arredondo-Bernal & Trujillo-Arriaga (1994).

A case of animal myiasis caused by M. scalaris in Crotalus durissus terrificus (Serpentes: Viperidae) was reported in Brazil (Silva et al. 1999). The finding of this species on myiasis in nasopharyngeal, intestinal, and leg wound in hospitalized patients in Kuwait and Egypt was recorded by several authors. However, most of the cases were considered as facultative and accidental (Singh & Rana 1989, Hira et al. 2004, Mazayad & Rifaat 2005).

In addition, according to Miller et al. (1994), specimens of M. scalaris obtained from corpses might be useful in forensic investigations to evaluate the post mortem interval and in toxicological analysis by using their puparium.

In this note, we present the first report of M. scalaris infesting colonies of Triatoma brasiliensis Neiva, the most important Chagas disease vector in the semiarid zones of northeastern Brazil (Costa et al. 2003).

The triatomine bugs were identified according to Lent & Wygodzinsky (1979) and the samples of M. scalaris were identified according to Disney (1994). Specimens of M. scalaris invaded the quadrangular plastic containers (10×10×10 cm) with perforated lids where two years-old colonies of T. brasiliensis (X = 40 samples) were being reared under laboratory conditions (temperature: min. 21.5ºC, max. 32ºC, X = 27.63ºC, relative humidity: min. 52%, max. 96%, X = 77.5%). Two weeks later, some triatomines with atypical darker color with stretched out proboscis and legs, were found moving slowly at the bottom of the containers. All the developmental stages of M. scalaris were found inside the containers of the triatomine colonies. Dead insects with these symptoms presented a strong putrid odor.

Eleven insects (two fifth-instar nymphs and nine adults) displaying the symptoms described above were isolated until death and then dissected, and internally observed using stereoscopic microscope Zeiss SV11, (X20). This procedure confirmed that larvae of M. scalaris were feeding inside T. brasiliensis. Two nymphs and four adults had their internal organs destroyed and no viscera could be found. Two other adults had semi-destroyed viscera where two pupae were found along the remains of the post mesenteric part of both specimens. Another adult had partial damage at the promesenteric portion, trachea, Malphigian tubules and rectal ampoule. Two pupae were found between the thoracic and abdominal portion where the connection between the esophagus and promesenteries should be seen. The remaining two specimens examined presented only a portion of the digestive system destroyed, and no pupae were found. All specimens had their thoracic muscles destroyed, even the specimens presenting visceral remains. This finding corroborates the supposition that insects infested by M. scalaris present difficulty to move due to the progressive loss of muscle tissue. Fig. 1 shows one of the specimens found at the bottom of the container after being infested by M. scalaris.

Due to the wide geographic distribution and ecologic plasticity of this phorid we suppose that M. scalaris specimens occurring naturally in the surroundings of the laboratory have invaded the colonies. As observed by Garris (1983) in tick colonies and also in our triatomine colonies, the presence of a double layer of organdy cloth did not prevent larvae of M. scalaris from invading the containers with the colonies. Eggs of M. scalaris were deposited through the cloth by penetration of the female ovipositor. In addition, this phorid has a short life cycle, 20 days or less in average, depending on temperature conditions (Rits 1997).

Because M. scalaris life cycle requires considerable levels of moisture to larval development (Trumple & Pienkowsky 1979) it is possible that the high density colonies of triatomines, presenting urine and bug excrements in the bottom of the container, may be an attractive condition and suitable for females to lay their eggs, as already indicated by Garris (1983). Here we suggest keeping the triatomine colonies in low population density and in drier conditions in order to impair M. scalaris infestations. Daily observation is required to avoid loss of large number of specimens from the triatomine colonies.

Thus, the finding of M. scalaris infesting colonies of T. brasiliensis brings up relevant aspects that must be investigated such as: (i) a surveillance to evaluate whether this phorid could also infest colonies of other triatomine species; (ii) the eventual possibility of M. scalaris to vehicle T. cruzi, the causative agent of Chagas disease; and (iii) the originator's factor responsible for the infestation of the colonies of T. brasiliensis by M. scalaris.



To Dr. Renato Andreotti e Silva, and Dr. Wilson Werner Koller, from the Empresa Brasileira de Pesquisa Agropecuária (Embrapa), for sending specific bibliography, and suggestions. To Dr. Brian Brown (Natural History Museum of Los Angeles County) for the valuable comments. To CNPq, Capes and Faperj for financial support.



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Received 29/X/06. Accepted 04/VI/07.

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