ACHERONTIA STYX MEDUSA Moore, [1858] -- Eastern Death's Head hawkmoth

Adult Acherontia styx medusa. Photo: © NHMUK

TAXONOMY

Acherontia medusa Moore, [1858], in Horsfield & Moore, Cat. Lepid. Ins. East India Company 1: 267. Type locality: [Indonesia,] Java [Jawa]; [Malaysia,] Pinang; [Central India,] Dukhun [Deccan]; [India, Tamil Nadu,] Madras [Chennai].

Synonym. Acherontia pseudatropos Röber, 1933.

Synonym. Acherontia styx crathis Rothschild & Jordan, 1903.

Synonym. Acherontia styx septentrionalis-chinensis Pavlov, 1932.

Note. Separation of Acherontia styx medusa from Acherontia styx styx Westwood in China is problematic because the two taxa appear to intergrade along a wide front. Specimens in the IZAS from Shanghai, Guangdong and Hong Kong are all typical Acherontia styx medusa, whereas those from Xizang/Tibet, Sichuan and Shaanxi are typical Acherontia styx styx. The intervening populations along this east-west divide are, to a greater or lesser extent, intermediate. Consequently, we do not allocate the following records to subspecies. Furthermore, Kitching & Spitzer (1995) stated that "specimens from Vietnam are somewhat intermediate between subspecies styx and medusa". It seems, therefore, that Acherontia styx medusa may just be a wet zone/season form.


ADULT DESCRIPTION AND VARIATION

Wingspan: 89--120mm. Although individually variable in colour and pattern, differs from Acherontia styx styx in having the tawny russet scaling of the forewing upperside reduced or absent. Similar to the European Acherontia atropos but differs in having two medial bands on the underside of the forewing, instead of one, and usually no dark bands across the ventral surface of the abdomen. The skull-like marking is darker and there is a faint blue tornal dot enclosed by a black submarginal band on the hindwing upperside. The forewing discal spot (stigma) is orange; in Acherontia atropos it is usually white.


Adult Acherontia styx medusa, Singapore. Photo: © Leong Tzi Ming

ADULT BIOLOGY

An avid robber of honey in bee hives (Pittaway, 1993); also, a fruit-piercing pest of yuzu (Citrus junos) in South Korea (Choi, Kim & Lim, 2000). Although not a regular migrant, limited numbers are found each year as far north as Heilongjiang. It favours hot, open, low-lying country, usually under semi-cultivation.


FLIGHT-TIME

Due to the difficulty of assigning many specimens to either Acherontia styx styx or Acherontia styx medusa, the below flight-times are a combination of both subspecies. (See "Global Distribution" for more details.)

China: iv (Jiangxi); vi (Guangdong; Jiangxi; Shandong); vii (Hainan); viii (Hubei); 7-9.viii (Zhejiang); 24-31.viii (Shanghai); ix (Jiangxi; Shaanxi); 1.x (Zhejiang). Taiwan: 2.vii (Kaohsiung Hsien); 12.vii (Chiai Hsien). South Korea: 3.viii. Japan: 26.vii (Shikoku); 22-23.viii (Shikoku; Honshu).

In both northeastern and southern China, there are two generations a year, with adults flying in May/June and August and larvae generally found from June until September.

Park et al. (1999) give late July until mid September as the flight period in Korea.


EARLY STAGES


A plate from Bainbrigge Fletcher, 1914

OVUM: Pale green, changing to yellowish green just before hatching. Oval (1.2 x 1.5mm), shiny and smooth. Laid singly on the under and upper surfaces of leaves on peripheral twigs, usually hatching three to five days later.

In India, the eggs of this species are often attacked by a hymenopterous parasite, which lays its eggs in or on those of the moth. Infected eggs become gradually mottled black and white as the larvae of the parasite develop. As many as twenty parasites may emerge from one egg (Bell & Scott, 1937).

LARVA: Full-fed 90--120mm. Trimorphic: green, yellow or brown.

The newly-hatched, 5mm-long larvae immediately consume their eggshells. At this stage they are 'frosty' yellowish green with a long, black, fork-tipped horn. In the second instar white lateral stripes and numerous small white tubercles appear. It is not until after the third moult that the final colours become apparent. Fully-grown larvae closely resemble those of Acherontia atropos except that the dark blue dorsal speckling is more pronounced on the anterior half of each abdominal segment, and the horn is less curved and lacks a reflexed tip.

In the green form, head dark green, with a broad, shiny black stripe down the cheek; labrum whitish with a black spot in the middle of each half; ligula whitish, the lobes streaked with black; basal segment of antenna white, middle segment white with black base, third segment pale red, mandible pale green with the tip broadly black. Segments 2 to 4 of body yellowish-green, but rest of body grass-green. Dorsum and sides of 5 to 11 with dark bluish dots along each secondary ring. There are seven sharply defined yellow oblique lateral stripes on 5 to 11, each stripe extending upwards and backwards to near the dorsal line of the segment behind, that on 11 extending backwards to the base of the horn; each stripe edged above with dark blue, sharply defined at the common edge but diffuse dorsad. Horn canary-yellow; true legs black; prolegs and claspers green; anal flap green edged with yellow. Spiracles oval, yellowish-white with the central slit black, the whole bordered with brownish-green (Bell & Scott, 1937).

In the yellow form, the green colour of head and body replaced by canary-yellow, but with the markings remaining the same.

In the brown form, head ochreous with the stripe dark brown. Body brown, with a broad black dorsal stripe onsegments 2 to 4 and below it a broad ochreous stripe. The subspiracular area dotted and streaked with brown; a brown oval marking on each side of the dorsum of 2. Oblique lateral stripes purple; horn ochreous, legs and prolegs black, claspers brown (Bell & Scott, 1937).

Larger larvae are lethargic and confine their strip-feeding to two or three shoots. At 40°C, growth is exceedingly rapid, ovum to pupa taking as little as 10 days.


Final instar light green form larva of Acherontia styx medusa. Image: Mell, 1922b Final instar dark green form larva of Acherontia styx medusa. Image: Mell, 1922b Final instar pale form larva of Acherontia styx medusa on Solanum torvum, Singapore. Photo: © Leong Tzi Ming Final instar pre-pupation form larva of Acherontia styx medusa, Singapore. Photo: © Leong Tzi Ming Final instar pre-pupation form larva of Acherontia styx medusa. Image: Mell, 1922b

PUPA: 50--60mm. Similar to, but paler than that of the European species Acherontia atropos. Antenna slightly longer than fore-leg. Cremaster stout, triangular, dorsal surface rugose, tip ending in two teeth, each bearing a bristle. However, unlike Acherontia atropos, rarely formed more than 10cm below the surface of the soil, in a smooth-sided chamber. The main overwintering stage. Very tolerant of extremes of moisture or dryness.


Pupa of Acherontia styx medusa (ventral view), Singapore. Photo: © Leong Tzi Ming Pupa of Acherontia styx medusa (lateral view), Singapore. Photo: © Leong Tzi Ming Pupa of Acherontia styx medusa (dorsal view), Singapore. Photo: © Leong Tzi Ming Pupa of Acherontia styx medusa (ventral view). Image: Mell, 1922b Pupa of Acherontia styx medusa (lateral view). Image: Mell, 1922b

Larval hostplants. Recorded in China from Clerodendrum, Ligustrum, Lycopersicon, Sesamum, Solanum and various Fabaceae (Mell, 1922b; Yang, 1978; Li & Guo, 1990).

Recorded in Korea on Solanum melongera, Solanum tuberosum, Capsicum annuum, Pisum sativum and Paulownia tomentosa (Park et al., 1999).

In Metro-Manila, the Philippines, uncommon in drier urban areas on compact saplings of the African ornamental tree Spathodea campanulata. However, this host is secondary to Vitex parviflora (Dvořák, 2014).

Elsewhere, most larval hostplants are Bignoniaceae, Fabaceae, Oleaceae, Pedaliaceae, Solanaceae and Verbenaceae, with occasional records from eleven other families. Solanum torvum and Clerodendrum have been recorded from Singapore (Leong & Tay, 2011).


PARASITOIDS

Unknown.


LOCAL DISTRIBUTION

Due to the difficulty of assigning many specimens to either Acherontia styx styx or Acherontia styx medusa, the below distributions are a combination of both subspecies. (See "Global Distribution" for more details.)

China: Hebei; Beijing; Shandong (Jinan; Yantai); Shanxi (Taigu; Xiaxian; Jiexiu; Changzhi); Shaanxi (Yangling; Xunyang, 1380m); Henan; Jiangsu; Shanghai; Zhejiang (Ningpo; Tianmu Shan); Hubei (Changyang; Yichang); Sichuan (Emei Shan; Gao Xian; Hongyuankun; Huili); Yunnan (Gaoligong Shan); Xizang/Tibet (Zhangmu, 2200m); Hunan; Jiangxi (Jiujiang; Nanchang); Guangdong (Foshan; Guangzhou; Shantou); Hong Kong; Guangxi; Hainan.

Taiwan: Chiai Hsien (Alishan); Kaohsiung; Kaohsiung Hsien (Liukuei).

North Korea. South Hamgyong Prov. (Wonsan).

South Korea: Seoul; Kyonggi Prov. (Suwon; Gwangleung; Deokeun-ri; Cheonma-san; Asan Bay; Ganam-myun; Geumdang-ri); Kangwon Prov. (Seolak-san; Chiak-san; Shillim; Yangyang; Daeam-san); North Chungchong Prov. (Chupungryung; Minjuji-san); South Chungchong Prov. (Gongju; Gyeryong-san); North Cholla Prov. (Byunsan; Mujugucheondong; Jiri-san; Naebyun-san; Unjang-san; Muju); South Cholla Prov. (Baekam-san; Baekyang Temple; Naju; Wolchul-san; Jogye-san; Geumo-do; Gurye; Yeocheon; Haenam); North Kyongsang Prov. (Daegu; Sobaek-san; Gimcheon; Juwang-san; Naeyon-san; Seongju; Cheongdo); South Kyongsang Prov. (Baekun-san; Gibaek-san; Hamyang; Jinyang; Muhak-san; Jinju; Geoje-do; Goseong; Namhae; Milyang; Sacheon; Sancheong; Uiryong; Hadong; Hapcheon); Cheju Prov. (Cheju-do).

Japan: Honshu (Mt. Mikabo); Shikoku (Matsuyama; Kajigamori); Kyushu; Tsushima; Ryukyu Archipelago (Okinawa).


GLOBAL DISTRIBUTION

The core distributions of the two subspecies are as follows. Acherontia styx medusa occurs throughout eastern continental Asia, from northeastern China (to where it is a migrant) and Japan, south through eastern China and Vietnam to Peninsular Malaysia and peninsular Thailand. Also found throughout the islands of the Malay Archipelago, from Sumatra, Borneo and the Philippines, east to the Maluku Islands. Acherontia styx styx occurs from north-central and western China westward across northern Thailand, Burma/Myanmar, Bangladesh, India, Nepal, Pakistan and Iran to Saudi Arabia and Iraq (Pittaway, 1993).


Global distribution of Acherontia styx medusa. Map: © NHMUK.

BIOGEOGRAPHICAL AFFILIATION

Palaeotropical; Oriental region.



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© A.R. Pittaway & I.J. Kitching (The Natural History Museum, London)