Dorsal fin with 13 spines and 9-11 rays (usually 10); anal fin with 3 spines and 6 rays; pectoral fins with 13-15 rays (usually 14); scales cycloid and small, 90-120 in longitudinal series; suborbital and preopercular bones of adults with spinous points; supraocular tentacle of variable length, rarely with faint bands; dorsal spines long, the longest clearly longer than body depth, each with membrane to tip but isolated from other spines except basally; pectoral membranes of adults broad and plumelike; numerous dark red to black bars of variable width on head and body (bars increasing in number with growth); small dark spots on soft rays of median fins; dorsal spines and membranes with dark red cross bands.

Reaches at least 30 cm.

From Red Sea and Arabian Gulf south to South Africa and east to Sumatra. At least 3 specimens have been reported from the east Mediterranean (Bariche at al. 2013). This species also represents a smaller part of the Pterois volitans/miles population in the western Atlantic that extends from Cape Hatteras (North Carolina) in the north to Venezuela in the south.

Usually found on coral reefs and rocky bottom or sand and seagrass in the vicinity of hard substrata from the shallows to at least 50 m. Individuals remain in the same general area of the reef a probably never leave it. It has been reported that in the Red Sea it feed on a variety of benthic fish, such as damselfish, cardinal fish and anthias. It stomach can expand more than 30 times when consuming a large meal. (Morris at al., 2009)
Morrris at al. (2009) with reference to Fishelson (1975) mentions that lionfish courtship includes circling, side winding, following, and leading. It begins shortly before dark and extends well into nighttime hours. Following the courtship phase, the female releases two buoyant egg masses that are fertilized by the male and ascend to the surface. The eggs and later embryos are bound in adhesive mucus that disintegrates within a few days, after which the embryos and/or larvae become free floating.
Most of the day the fish spend in caves and under ledges but later in the afternoon they come out. However, young specimens may be seen hunting in water column in shallow lagoons even during the day. It is not an exception that more individuals rest or hunt together. If approached when resting, an adult specimen usually raises its dorsal spines but otherwise remains calm. Also during the active period it reacts to human presence by raising the dorsal spines but usually moves around and may even move slowly toward the intruder. It is advisable to go out of its way. If the fish stands on its head, so to say, and points the dorsal spines toward the intruder, it may well be the last warning before it attacks. It can strike very rapidly. P. miles as well as its close relative P. volitans should always be treated with extreme caution.

Lionfish spines (i.e. 13 dorsal spines, 3 anal spines, and 2 pelvic spines) contain apocrine-type venom glands. The toxin in lionfish venom contains acetylcholine and a neurotoxin that affects neuromuscular transmission. The venom causes cardiovascular, neuromuscular, and cytolytic effects ranging from mild reactions such as swelling to extreme pain and paralysis in upper and lower extremities. Antivenom of the related stonefish (Synanceia ssp.) is highly effective in neutralizing lionfish venom activity. The severity of sting reactions in humans is dependent upon such factors as the amount of venom delivered, immune system of the victim, and the location of the sting. The probability of lionfish envenomation is higher when handling smaller-sized lionfish because the venom glandular tissue is closer to the tip of the spine and the spine tip is smaller and sharper.
It is of interest that lionfish venom (P. volitans) contains antitumor, hepatoprotective, and antimetastatic effects in mice suggesting a promising application for cancer research.

P. volitans is almost identical but it usually has 11 dorsal and 7 anal fin rays while P. miles specimens usually have 10 dorsal and 6 anal fin rays. Also, P. volitans has significantly larger pectoral fins and larger spots on the soft vertical fins (Schultz 1986). The native geographic range of P. miles extends from South Africa north and east along the coasts of southern Asia to Indonesia in the Indian Ocean. Pterois volitans is found in the tropical Pacific from the Pitcairn group in the east to Indonesia in the west, and along the western coast of Australia in the Indian Ocean. Randall (1995) makes the following observation: "At present there is no overlap in their distributions. It will be of interest to see if they coexist in the present gap of their distribution in Indonesia between Sumatra and Sulawesi." Recent studies (Freshwater at al. 2009; Kulbicki at al. 2012) indicate that the range of these two species overlap in western Indonesia, namely in the waters of Java, Sumatra, and Malay Peninsula.
The correct identification of the species may be based on geographic location. For example, a diver in the Red Sea can be sure that what he sees is Pterois miles. However, in the relatively small area where the range of the two species overlap or in the western Atlantic where these two species have become invasive, the correct identification is next to impossible.

In connection with the taxonomy of P. miles and P. volitans, Gonzáles at. al (2009) note: "While traditional taxonomy indicates that Pterois volitans (Linnaeus 1758) (or red lionfish) and P. miles (Bennett 1828) (or devil firefish) comprise two different valid species (Schultz 1986), recent molecular studies suggest that there is uncertainty in determining whether the two entities represent species or populations (Kochzius et al. 2003; Whitfield et al. 2007)." Freshwater at al. (2009) report: "Specimens with counts typical of both species as well as mixed meristics – P. volitans dorsal fin ray count and P. miles anal fin ray count, and vice versa – have been collected (Whitfield unpubl. data, Morris unpubl. data, Freshwater unpubl. data)."