To the biology of Acerocnema breviseta (Zetterstedt, 1846) (Diptera: Scathophagidae), with description of immature stages

Russian Entomol. J. 33(3): 401–406 © RUSSIAN ENTOMOLOGICAL JOURNAL, 2024 ABSTRACT. The biology of Acerocnema breviseta (Zetterstedt, 1846) was studied. Larvae were collected in Moscow Region (Russia) in May by the way of sorting the seeds of Corydalis solida (Papaveraceae). Mature larvae at that moment left the fruits before pupation. The morphology of the third instar larva and puparium was studied and described for the fi rst time for the genus and species. РЕЗЮМЕ. Изучена биология мухи-скатофагиды Acerocnema breviseta (Zetterstedt, 1846). Личинки были обнаружены при сортировке семян хохлатки плотной Corydalis solida (Papaveraceae). Взрослые личинки в тот момент покидали плоды перед окукливанием. Изучена морфология личинки 3-го возраста и пупария, которые впервые для рода и вида описываются в данной работе. Introduction Acerocnema Becker, 1894 is one of the small genera within the family Scathophagidae, which until the present time has comprised 15 species distributed in the Holarctic Region [Iwasa, 2014; Ozerov, Krivosheina, 2018; Chagnon, Sinclair, 2021]. Nine species are registered in Russia [Ozerov, Krivosheina, 2023]. The data on the biology of Acerocnema species are very poor. Adults were mainly captured on fl owering Corydalis plants but only for Acerocnema macrocera (Meigen, 1826) females ovipositing eggs on fruits of Corydalis solida were observed in Europe [Mortelmans, Devillers, 2014]. Our study is related to the description of the third instar larva and puparium of the Acerocnema breviseta (Zetterstedt, 1846), which is done for the fi rst time for the genus and species. Terminology follows Zimin [1948] and Teskey [1981]. Material and Methods The collection of the imaginal material took place in 2012, 2019, 2023 and 2024 in the Moscow region (Shakhovskoy district, outskirts of Andreevskoe village (55.9815°N 35.5972°E), Burtsevo vicinity (55.9814°N 35.5972°E) and the outskirts of Rozhdestveno village (55.9349°N 35.6289°E), as well as in Moscow in Filevsky Park (55.7424°N, 37.4 392°E) on fl owering plants of Corydalis solida (Papaveraceae) or near them. In total, 12 ♂♂ and 13 ♀♀ were collected. All adults of both sexes were determined as Acerocnema breviseta (Figs 1–3). The fi rst 6 larvae were collected 15.V.2023 in Moscow region, Burtsevo vicinity (55.9814°N 35.5972°E)) during sorting of seeds of Corydalis solida; 5 larvae pupated; one larva and one puparium were fi xed in alcohol [alcohol 1]. On the 17.V.2023, at the same place, three more larvae were added to this test tube with a larva in alcohol. Two more larvae were found in Moscow region, env. Rozhdestvenno (55.9349°N 35.6289°E) on the 18.V.2023. One of the larvae was eating a Corydalis seed (Fig. 12); both larvae were fi xed in alcohol [alcohol 2]. On the night of 30.VI.2023 out of four puparia, two were placed in the refrigerator (upper compartment in the door, To the biology of Acerocnema breviseta (Zetterstedt, 1846) (Diptera: Scathophagidae), with description of immature stages Ê áèîëîãèè Acerocnema breviseta (Zetterstedt, 1846) (Diptera: Scathophagidae), ñ îïèñàíèåì ïðåèìàãèíàëüíûõ ñòàäèé A.L. Ozerov1*, M.G. Krivosheina2 À.Ë. Îçåðîâ1*, Ì.Ã. Êðèâîøåèíà2 1 Zoological Museum, Moscow Lomonosov State University, Bol’shaya Nikitskaya 2, Moscow 125009, Russia. 1 Зоологический музей, Московский государственный университет им. М.В. Ломоносова, Большая Никитская ул., 2, Москва 125009, Россия. 2 A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Leninsky prospect, 33, Moscow 119071 Russia. 2 Институт проблем экологии и эволюции им. А.Н. Северцова РАН, Ленинский проспект, 33, Москва 119071 Россия. Andrei Ozerov [email protected] ORCID 0000-0003-0889-5024 Marina Krivosheina [email protected] ORCID 0000-0001-9064-1378 *corresponding author KEY WORDS: Diptera, Scathophagidae, Acerocnema, breviseta, larva, puparium, description, biology. КЛЮЧЕВЫЕ СЛОВА: Diptera, Scathophagidae, Acerocnema, breviseta, личинка, пупарий, описание, биология. How to cite this article: Ozerov A.L., Krivosheina M.G. 2024. To the biology of Acerocnema breviseta (Zetterstedt, 1846) (Diptera: Scathophagidae), with description of immature stages // Russian Entomol. J. Vol.33. No.3. P.401–406. doi: 10.15298/rusentj.33.3.13 A.L. Ozerov, M.G. Krivosheina 402 t° = 4.8–5.8 °C), the other two were left in test tubes in a room at a temperature of ~20 °C. On the 16.VII.2023 puparia from the refrigerator (two puparia) were moved to the freezer (t° = –15 … –18 °C) for a period of 4 weeks (until 13.VIII.2023). On the 13.VIII.2023 the puparia from the freezer were moved below to a compartment with a temperature of 4.8–5.8 °C for a period of 4 months (until 13.XII.2023). Then the larvae were kept at temperature 23–25 °C. Special care was taken to ensure that the substrate in which the larvae were located (Sphagnum sp.) was moist. We managed to hatch only one fl y which emerged on the 13.I.2024 and was determined as Acerocnema breviseta. Results BIOLOGY. Adults of both sexes (Figs 1–3) are found during spring (last April – early May). The fl ies are encountered in places with Corydalis solida (L.) Clairv., 1811 (fam. Papaveraceae) (Figs 4–6). The life history of this species can be summarized as follows: adults emerge from overwintering pupae from the middle of April and, after mating, lay eggs to seeds of Corydalis solida from the late of April to early of May. Larvae apparently penetrate the seed of Corydalis solida (Fig. 4) to consume its contents through the micropyle (Fig. 12). Mature (three instar) larvae leave the fruit and form their puparia in wet soil. There is only one generation a year; puparia are formed in middle–late May and overwinter at this stage. DESCRIPTION OF IMMATURE STAGES. Third instar larva. Body length 4.7 mm, maximal width 1.2 mm. Body shape cylindrical, tapering anteriorly. Creamy white, integument regularly covered with transparent spinules (Fig. 11). Creeping welts are not developed. Anterior spiracles bicornuate, each cornu with 7–8 papillae (Fig. 9). Cephalopharyngeal skeleton strongly sclerotized and massive (Fig. 8). Mandibles large without accessory dents. Hypopharynx short. Pharyngeal sclerite with dorsal cornu longer than the ventral. Dorsal cornu with narrow thin long window. Ventral cornu with large open window. Terminal segment of the body with two short respiratory tubes. Spiracular plates fl at without developed spines, each with three identical radial spiracular openings (Fig. 10). Terminal segment with 5 pairs of tubercles. Perianal pad transverse, anus is situated in a longitudinal cleft. Puparium. Body length 4.0 mm, maximal width 1.1 mm. Body shape cylindrical, tapering and bilobed anteriorly (Fig. 16). Brown, integument regularly covered with dark spinules. Creeping welts are not developed. Anterior spiracles bicornuate, each cornu with 7–8 papillae. Cephalopharyngeal skeleton as in third instar larva (Fig.8). Terminal segment of the body (Figs 13–15) with two short respiratory tubes. Spiracular plates fl at without developed spines, each with three radial spiracular openings (Fig. 10). Terminal segment with 5 pairs tubercles 4 of them (dorsal, lateral, subventral, subanal) are large and fl eshy, ventral tubercles are small (Figs 13–15). Perianal pad brown, transverse, anus is situated in a longitudinal cleft (Figs 15, 16). Figs 1–3. Acerocnema breviseta (Zetterstedt), adults: 1 — male (collection specimen), lateral view; 2 — male on a stem of Corydalis solida; 3 — female in grass near Corydalis solida. Рис. 1–3. Acerocnema breviseta (Zetterstedt), имаго: 1 — самец (коллекционный экземпляр), сбоку; 2 — самец на стебле Corydalis solida; 3 — самка на траве около Corydalis solida. To the biology of Acerocnema breviseta (Diptera: Scathophagidae) 403 Figs 4–7. Corydalis solida (L.) Clairv.: 4 — general view; 5 — infl orescence with fl owers; 6 — same, with fruits; 7 — fruits (on the left, an open fruit with seeds). Рис. 4–7. Corydalis solida (L.) Clairv.: 4 — общий вид; 5 — соцветие с цветками; 6 — то же, с плодами; 7 — плоды (слева вскрытый плод с семенами). A.L. Ozerov, M.G. Krivosheina 404 Discussion Despite the name of the family Scathophagidae, or “dung fl ies”, larvae only from genera Scathophaga Meigen, 1803 and Scatomyza Fallén, 1810 live in dung; the known representatives of the other genera are mainly phytophagous [Ferrar, 1987]. Larvae of the genus Cordilura Fallén, 1810 in fi rst instar are phytophagous, but in second and third instars are saprophagous [Wallace, Neff, 1971]; some larvae, for example Cleigastra apicalis (Meigen, 1826), inhabiting tunnels of other insects, are supposed to be saprophagous, although some authors consider them to be scavengers or predators [Ferrar, 1987; Grochowska, 2006]; larvae of Cosmetopus longus are detritophagous [Ferrar, 1987]; larvae of the genus Spaziphora Rondani, 1856 are predaceous [Ferrar, 1987]. Depending on the type of diet and life habits, the larvae have morphological differences in the structure of the cephalopharyngeal skeleton and general morphology. Figs 8–12. Acerocnema breviseta (Zetterstedt), third instar larva: 8 — cephalopharyngeal skeleton; 9 — cephalic segment, ventral view; 10 — posterior spiracles; 11 — general view, laterally; 12 — larva eating the seed of Corydalis solida. Рис. 8–12. Acerocnema breviseta (Zetterstedt), личинка 3-го возраста: 8 — ротоглоточный скелет; 9 — передний конец тела, снизу; 10 — задние дыхальца; 11 — общий вид, сбоку; 12 — личинка, поедающая семя хохлатки Corydalis solida. To the biology of Acerocnema breviseta (Diptera: Scathophagidae) 405 Larvae of A. breviseta are carpophagous and share most of the morphological characters with phytophagous larvae of the family Scathophagidae. Anterior spiracles of A. breviseta are of a shape close to those of Norellisoma spinimanum (Fallén, 1819), differing from it by the number of papillae: 7–8 on each cornu in A. breviseta and 13 in N. spinimanum [Ferrar, 1987]. Massive mouthhooks are typical of many phytophagous larvae, such as Neochirosia atrifrons (Coquillett, 1910), most species of Cordilura, Cleigastra armillata (Zetterstedt, 1846), N. spinimanum. Species of fi rst three genera have additional tooth on the mouth hooks Figs 13–16. Acerocnema breviseta (Zetterstedt), puparium: 13 — terminal segment, lateral view; 14 — same, posterior view; 15 — same, ventral view; 16 — general view, ventrally. Abbreviations: an pl — anal plate; dor tub — dorsal tubercle; lat tub — lateral tubercle; suban tub — subanal tubercle; subv tub — subventral tubercle; ven tub — ventral tubercle. Рис. 13–16. Acerocnema breviseta (Zetterstedt), пупарий: 13 — задний конец тела, сбоку; 14 — то же, сзади; 15 — то же, снизу; 16 — общий вид, снизу. Сокращения: an pl — анальная пластинка; dor tub — дорсальный бугорок; lat tub — латеральный бугорок; suban tub — субанальный бугорок; subven tub — субвентральный бугорок; ven tub — вентральный бугорок. A.L. Ozerov, M.G. Krivosheina 406 [Ferrar, 1987]. Mouthhooks of A. breviseta larvae lack such tooth and this character makes them similar to the larvae of N. spinimanum. However ventral cornua of pharyngeal sclerite in A. breviseta are relatively shorter and less massive, than in N. spinimanum, and with open, not closed, window. Spiracular plates of posterior spiracles are without spines, each with three identical radial spiracular openings (Fig. 10). The puparium is cylindrical in shape, uniformly tapering anteriorly, and is most similar to puparia of the genus Cordilura Fallén, 1810. Similar shape of the puparia is known also for Cleigastra apicalis, described by Grochowska [2006]. However the puparia differ in the morphology of creeping welts, well developed in C. apicalis, but absent in A. breviseta. This can be explained due to the differences in the larvae habits: C. apicalis move actively inside tunnels of other insects and A. breviseta leads a semisubmerged mode of life. Competing interests. The authors declare no competing interests. Acknowledgements. The investigation was fulfi lled within the State project of Lomonosov Moscow State University No 121032300105-0 (A.L. Ozerov) and the state project of the Institute of the Ecology and Evolution RAS (M.G. Krivosheina). References Chagnon M.-E., Sinclair B.J. 2021. Revision of Nearctic species of Acerocnema Becker (Diptera: Scathophagidae) // Zootaxa. Vol.4952. No.3. P.523–539. doi: 10.11646/zootaxa.4952.3.5 Ferrar P. 1987. A guide to the breeding habits and immature stages of Diptera Cyclorrhapha // Entomonograph. Vol.8. Part.1–2. 907 pp. Grochowska M. 2006. Remarks on the morphology and biology of Cleigastra apicalis (Meigen, 1826) (Diptera, Scathophagidae) // Acta Zoologica (Stockholm). Vol.87. P.247–252. Iwasa M. 2014. Three new species of the genus Acerocnema Becker (Diptera: Scathophagidae) from Japan, with a key to the Palaearctic species // Studia Dipterologica. Vol.20. No.2. 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