First record of Scuttle fly, Megaselia (M) scalaris (Loew) (Diptera: Phoridae) as a parasitoid of Sunn pest, Eurygaster integriceps Puton (Hemiptera: Scutelleridae) from Iran

Abstract

The Scuttle fly, Eurygaster integriceps Puton (Hemiptera: Scutelleridae) is a key pest of wheat and barley. The pest is univoltine and migrates from wheat fields following harvest to high elevations; then, the following spring it moves back to the fields. Natural enemies may have an important role in decreasing the population’s level in overwintering sites. In the present study, adults of E. integriceps were collected from overwintering sites in Isfahan province, Iran, in October 2022 and transferred to the laboratory. One week after sampling, dead adults were isolated and divided into three groups: one group was dissected under a stereomicroscope, and parasitoid larvae were extracted from the cadavers; the second one was incubated in Petri dishes sealed with parafilm, individually for four weeks, and emerged pupae were collected; and the third group was incubated in the closed boxes, and emerged flies were collected for fixing and identification. Assessment of dissected adult E. integriceps under a stereomicroscope revealed that the insect was parasitized with Megaselia scalaris (Loew) (Diptera: Phoridae) larvae. Per adult, up to 13 larvae were found inside E. integriceps. The last instar larvae were pupated outside the E. integriceps body. This study is a new record of M. scalaris as a parasitoid of E. intergriceps in Iran.

The Scuttle fly, Eurygaster integriceps Puton (Hemiptera: Scutelleridae) is an economically important insect pest of wheat and barley in West and Central Asia, Eastern Europe, and North Africa (Davari & Parker 2018). Estimated yield loss caused by high populations of E. integriceps reaches 20–30% in barley and 50–90% in wheat and can reach 100% in the absence of control actions (Davari & Parker 2018). Natural enemies have the greatest effect among the factors restraining the Sunn pest population (Iranipour et al. 2011). Several general and specialized natural enemies attack different life stages of E. integriceps. Hymenopteran egg parasitoids, especially those of the genus Trissolcus sp. (Scelionidae) and tachinid flies (Diptera: Tachinidae) as parasitoids of adults and nymphs, are the most important parasitoids of E. integriceps (Davari & Parker 2018).

Phoridae have more than 4000 world species, and the largest genus in this family is the genus Megaselia with over 1700 species worldwide (Namaki-Khameneh et al. 2021). Megaselia scalaris (Loew) (Diptera: Phoridae) is an omnivorous cosmopolitan species, whose larvae occur in a large variety of environments and ecological niches and develop on living and decayed materials with plant or animal origin (Namaki-Khameneh et al. 2021). Ever more, larvae of M. scalaris can become facultative predators, parasitoids, or animal and human parasites (Disney 2008). This species has medical and forensic importance because of its role in animal and human myiasis and its colonization of human corpses (Varney and Noor 2010). Recently, the use of M. scalaris in genetics and developmental biology studies has increased (Mukherjee et al. 2019). Moreover, parasitism of some insect species of agronomic and medical importance from different orders including Hymenoptera, Hemiptera, Orthoptera, Mantodea, Lepidoptera, Diptera, and Coleoptera has been reported by El-Hawagry et al. (2021).

Megaselia scalaris has been reported from Iran as a button mushroom (Agaricus bisporus) pest (Zamani et al. 2005), as a parasitoid of the Iranian honey bee, Apis mellifera meda (Hymenoptera: Appidae) (Abdi-Goodarzi et al. 2013), human Urogenital Myiasis (Ghavami and Djalilvand 2015) and ectoparasite of larvae of Polyphylla adspersa (Coleoptera: Melolonthidae) (Karimi et al. 2019).

The aim of this study was to report M. scalaris parasitizing E. integriceps, as a new host in Iran. Adults of E. integriceps were collected from Jozdan, Isfahan province, Iran (52°72′N, 35°97′E, and alt. 2250), during October 2022. The insects were transferred to the laboratory and kept in closed boxes with ventilated lids at 25 ± 1 °C and RH = 75%. One week after sampling, dead adults were collected from the boxes; divided into three groups. One group was dissected under an Olympus SZH stereomicroscope and parasitoid larvae were extracted from the cadavers. The second group was incubated in Petri dishes sealed with parafilm, individually for four weeks, and emerged pupae were collected. The third group was incubated in the closed boxes, and emerged flies were collected. The collected insects were fixed in 90% ethanol and used for identification.

Examination of adult E. integriceps under a stereomicroscope revealed insect parasitized with M. scalaris larvae. More than one larva in the body of each dead E. integriceps (Fig. 1) was found (gregarious parasitoid). Up to 13 larvae were found inside the body of one adult E. integriceps. The larvae inside the body were in different sizes ranging from 1 to 4.5 mm in length and 0.2–1 mm in width (Fig. 2). The last instar larvae pupated outside the E. integriceps body (Fig. 3), and the adults emerged from the puparium (Fig. 4) after about 14 days under laboratory conditions. Females were larger than males (Fig. 5).

Fig. 1

Parasitized adult Eurygaster integriceps with Megaselia scalaris larvae in different sizes inside the body (M. scalaris larvae are shown with small black arrows)

Fig. 2

Different larval stages of Megaselia scalaris extracted from adult Eurygaster integriceps cadaver

Fig. 3

Pupae of Megaselia scalaris parasitized Eurygaster integriceps

Fig. 4

Puparium of Megaselia scalaris after adult eclosion

Fig. 5

Adult female and male Megaselia scalaris parasitized Eurygaster integriceps

This study represents a new record of M. scalaris as a parasitoid of E. intergriceps. Parasitism of some insect species from different orders has been reported. However, reports on hemipteran insects are limited to a few species including Triatoma brasiliensis (Reduviidae) (Costa et al. 2007), Palomena prasina (Pentatomidae) (Özdemir and Tuncer 2020), and Nezara viridula (Pentatomidae) (El-Hawagry et al. 2021). In agreement with our results, in all the mentioned studies, the adult hemipterans were parasitized and more than one larva of M. scalaris was found inside the parasitized hemipteran hosts. However, El-Hawagry et al. (2021) reported more than 40 larvae of M. scalaris from one parasitized N. viridula.

Over 15 million hectares in Iran, Turkey, Iraq, Syria, Lebanon, Jordan, Israel, Kazakhstan, Uzbekistan, Kyrgyzstan, Tajikistan, Afghanistan, and Pakistan is infested by the Sunn pest (Davari & Parker 2018). In infested areas, the main control strategies have heavily relied on chemical insecticides (Alizadeh et al. 2022). Considering the overuse of insecticides against E. integriceps, and the problems related to the pest resistance, environmental pollution, and consequently, human health hazards, reconfirm the importance of seeking alternative pest control strategies, especially with the emphasis on natural enemies. M. scalaris was reported in the present study, as a parasitoid of E. integriceps, although further works are expected to be done on the relationship between M. scalaris and E. integriceps, especially the rate of natural parasitism in the overwintering sites of E. integriceps, as well as on the biological parameters of the parasitoid species.