Scuttle fly Megaselia scalaris (Loew) (Diptera: Phoridae) endoparasitoid as a novel biocontrol agent against adult American cockroaches (Periplaneta americana)

Abstract

The American cockroach, Periplaneta americana (Linnaeus, 1758) (Blattodea: Blattidae), is one of the most common pests that thrive in diverse environments and carries various pathogens, causing critical threats to public health and the ecosystem. We thus report in this study the first observation of decapitated American cockroaches as a result of infestation with scuttle fly parasitoids. Interestingly, behavioral alterations in the form of zombification-like behavior could be observed in cockroaches reared in the laboratory before being decapitated, implying that the insect targets cockroach heads. To identify this parasitoid, cockroaches' corpora were isolated in jars, and apodous larvae were observed. Larvae developed into small coarctate pupae, and adults emerged. The scuttle flies were collected and exhibited tiny black, brown, to yellowish bodies. The fly was initially identified based on its morphological properties as a member of the order Diptera, family Phoridae. To provide further insights into the morphological attributes of the phorid species, the fly was examined using a scanning electron microscope (SEM) and then identified as Megaselia scalaris accordingly. SEM analysis revealed the distinctive structure of M. scalaris concerning the head, mouth parts, and legs. Specifically, the mouth parts include the labrum, labellum, rostrum, and maxillary palps. Although further investigations are still required to understand the complicated relationships between M. scalaris and American cockroaches, our findings provide a prominent step in the control of American cockroaches using M. scalaris as an efficient biological control agent.

Keywords: Periplaneta americana; American cockroach; Biological control; Scanning electron microscope; Scuttle fly Megaselia scalaris; Zombification behavior.

Figure 1

(A–D) Photographs of yellowish-black larvae of M. scalaris reared from dead cockroaches corpuses in jars.

Figure 2

(A) Adult female M. scalaris is on the left side and male M. scalaris is on the right side. (B) abdominal tergites of the M. scalaris female.

Figure 3

SEM micrograph of the adult female M. scalaris showing the ventral view of the whole fly body.

Figure 4

SEM micrograph of the mouthpart structures of female M. scalaris illustrates the labrum (red arrow), labellum (blue arrow), rostrum (white arrow), and maxillary palp (dark arrow).

Figure 5

SEM micrograph of the mouthpart structures of the female M. scalaris. The ventral view at higher magnification shows the medius membranous lobe (yellow arrow), long trichoid sensilla in a lateral position (black arrow), short in the ventral position (red arrow), the smooth labellum surface without microtrichia (star), and hooks in the food channel (blue arrows).

Figure 6

SEM micrographs of the M. scalaris head structure show the third antennal segment or the first flagellar segment (red arrows), the arista (white arrows), and the compound eyes (blue arrows). (A) and (B) Frontal views of the head structure, while (C) merged SEM micrographs for both (A) and (B) for better visualization of the whole head region of the fly. (D) Lateral view of the head region.

Figure 7

(A) and (B) SEM micrographs of female M. scalaris Illustrate ventral view of female ovipositor.

Figure 8

(A) SEM micrograph of male M. scalaris shows the whole bodies of the male scuttle flies and (B) SEM micrograph of male M. scalaris displays the apex of the male abdomen.

Figure 9

SEM micrograph of the M. scalaris shows haltere.

Figure 10

SEM micrographs of M. scalaris hind leg structure. (A) Hind femur, tibia, and tarsus. (B) and (C) SEM micrographs of M. scalaris hind tarsus, with enlarged pretarsal segment, respectively.

Figure 11

Several characteristics of P. americana were observed in this study as a consequence of infection with scuttle flies. (A) Decapitated P. americana with the entire body present. (B) P. americana with only the metathorax and abdomen present. (C) Separated head of the P. americana. (D) P. americana with only the pronotum and wings present.