Megacrania batesii

M. batesii has been observed to feed on three species of Pandanaceae in the wild: Benstonea monticola, Pandanus solms-laubachii, and P. tectorius. The presence of these phasmids can be inferred by detecting the feeding scars they leave on the plants, which are readily distinguishable from those of the few other insects that feed on them. In captivity, they have been observed to feed on unspecified species of Freycinetia, as well as P. gemmifer, P. utilis, and P. whitei.[1]

Although these insects can inflict a great deal of damage to the plants upon which they feed, they are not typically considered to be pests because the host plant is not of significant economic importance.[11] That said, at least one example has been reported in which an infestation of stick insects — possibly M. batesii — in Capiz Province on Panay Island in the Philippines has resulted in the destruction of pandanus plants used in the manufacture of mats.[4][5]

Predators of this insect include huntsman spiders, jumping spiders, scolopendrid centipedes, green tree ants, mantises, katydids, and black butcherbirds. Throughout their distribution within Queensland, eggs of M. batesii have been observed to be parasitized by eupelmid wasps of genus Anastatus.[1]

The vast majority of specimens observed and collected in the wild are female, with male specimens being uncommon. Parthenogenesis appears to be the primary means of reproduction in some populations of M. batesii,[10] although sexual reproduction has been observed in other populations, including in captivity.[1]

There are roughly 2500 known species of stick insects. These large and often apterous insects are vulnerable to predators because they are slow and clumsy. Most species employ crypsis (for example, they are usually colored and shaped like twigs and leaves) as a primary defense mechanism. Only a few known species are aposematically colored or protected by defensive scent glands.[12]

In addition to its aposematic coloration, M. batesii possesses a robust chemical defense mechanism.[13] When sufficiently provoked (especially when the thorax and abdomen are touched) or when cornered by a perceived predator, these insects can spray an aerosolized cloud of noxious sticky white fluid from a pair of glands located at the prothorax.[13]

In an early description of a closely related species (Megacrania wegneri) in the Maluku Islands of Indonesia, Wegner reported that even immature phasmids were already in possession of a well-developed chemical defense mechanism. He noted that the noxious effluvium could be directed in front of the insect as well as to the rear. He further noted that the female was able to eject the substance as far as 75 centimeters (30 in), and even the considerably smaller male can spray up to 50 centimeters (20 in). Wegner also carefully described the paired prothoracic glands — these are pits located on the left and right side, dorsolaterally, at the anterior margin of the prothorax. When threatened, the phasmid contracts a muscle that extrudes a dome-shaped membrane through these pits. This membrane serves as a nozzle through which two jets of aerosolized fluid can be sprayed in either a forward or backward direction, depending on from where the insect perceives the threat.[14][15]

A few other phasmid species possess a chemical defense mechanism involving the secretion of a noxious fluid from a pair of prothoracic glands when disturbed. In nearly every species of phasmid studied thus far, the active components of these secretions appear to be cyclopentanoid monoterpenes.[12] The only known exceptions to this rule are Oreophoetes peruana and Cryptophyllium westwoodii. Quinoline is the active component in the former,[12] while the secretions of the latter contain various alkylpyrazines.[16]

Examples of phasmids which secrete cyclopentanoid monoterpenes from their prothoracic glands include several species of genus Anisomorpha, which secrete anisomorphal.[17][18][19] Other examples include Megacrania alpheus, Megacrania nigrosulfurea, and Megacrania tsudai, three species closely related to M. batesii that possess a nearly identical chemical defense mechanism. Actinidine is the chief component of the substance secreted by the prothoracic glands of these three species.[20][21][22][23]