ACHERONTIA STYX (Westwood, 1847)


ACHERONTIA STYX STYX (Westwood, 1847)

GB: Eastern Death's Head hawkmoth

Sphinx styx Westwood, 1847, Cabinet oriental Ent.: 88.

Type locality: East Indies.


A plate from Walker & Pittaway (1987).

BIOGEOGRAPHICAL AFFILIATION

Palaeotropical; Oriental region.


ADULT DESCRIPTION AND VARIATION

Female Acherontia styx, Ras Tanura, eastern Saudi Arabia.

Wingspan 90--120mm. Similar to A. 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 A. atropos it is usually white. Variation as in A. atropos.


Acherontia styx. Photo: © Jean Haxaire.

ADULT BIOLOGY

In behaviour, very similar to that of A. atropos. An avid robber of honey in bee hives in Oman (Pittaway, 1993). Although not a regular migrant like A. atropos, limited numbers are found each year throughout the Middle East. It favours hot, open, low-lying country, either under semi-cultivation, or with oases.


FLIGHT-TIME

February, May, July and September, occurring in four generations, although in Saudi Arabia, adults and larvae may be found until November in small numbers (Pittaway, 1979b).


EARLY STAGES

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

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


Full-grown larva of A. styx, Ras Tanura, eastern Saudi Arabia. Photo: © Tony Pittaway

As in A. atropos, 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, many more than in A. atropos. Additionally, young larvae of A. styx never bear the dorsal, thoracic, thorn-like tubercles so pronounced in that species. As in A. atropos, it is not until after the third moult that the final colours become apparent. Fully-grown larvae closely resemble those of A. 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 colour forms and behaviour, A. styx also resembles the previous species, being, if anything, more lethargic and confining its strip-feeding to two or three shoots. At 40 degrees C, growth is exceedingly rapid, ovum to pupa taking as little as 10 days. Usually found from March to mid-November. (For more information see Harbich (1978a, 1978b, 1980c, 1981).)

Major Hostplants. Solanaceae (especially Lycopersicon, Solanum, Lycium and Withania somnifera) and some Verbenaceae, such as Clerodendrum inerme, a common hedging plant in the Arabian Peninsula (Pittaway, 1981).

Minor Hostplants. Oleaceae, Cucurbitaceae, Fabaceae and Sesamum indicum, and, in the gardens of Saudi Arabia, Spathodea campanulata, Tecoma stans, Tecomaria capensis, Lantana camara, Vitex agnus-castus and Duranta erecta (Pittaway, 1993). The last also in Iraq.

PUPA: 50--60mm. Similar to, but paler than that of A. atropos. However, unlike that species, 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 styx, Saudi Arabia. Photo: © Tony Pittaway. Pupa of Acherontia styx styx. Image: © Tony Pittaway.

PARASITOIDS

Tachinidae: Drino (Zygobothria) atropivora (Robineau-Desvoidy), D. (Z.) ciliata (Wulp) (Whitcombe & Erzinclioglu, 1989).


Tachinid fly (Drino (Zygobothria) atropivora) reared from the final instar larva of Acherontia lachesis lachesis, Singapore. Photo: © Leong Tzi Ming.

DISTRIBUTION

Lower Mesopotamia (Wiltshire, 1957), Saudi Arabia (Pittaway, 1979b; Wiltshire, 1980a), eastern Oman (Wiltshire, 1975a), western and southern Iran (Ghassemi, Alemansoor & Alehossein, 2009) and eastern Afghanistan (Ebert, 1969); as a migrant, it has been found in Turkey, Syria (Wiltshire, 1980b) and Jordan (Pittaway, 1993; Müller et al., 2005a). A. styx has recently (1982) spread right across Saudi Arabia to Jeddah (Wiltshire, 1986), and may well colonize the African mainland in the near future.

Extra-limital range. Pakistan (Rafi et al., 2014), India, Sri Lanka, Bangladesh, Myanmar, Thailand and Yunnan Province, China.



OTHER SUBSPECIES

Southern Japan, central and eastern China, Indo-China, Philippines, Malaysia and western Indonesia as subsp. medusa Butler, 1877.


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