Do they spit the acid from their mouths, or from a separate sac or what, do you know?
*shudder*
This is a pair of Two-lined Walkingsticks, Anisomorpha buprestoides, also known as Musk-Mares or Devil Riders because of their habit of remaining in coitus for extremely long periods of time. The male is much smaller than the female. Beware!! They do not bite but they can spray a noxious substance from their necks that is painful if it gets in your eye.
Eisner (1965) reported that the stick insects generally discharged the secretion as a result of certain perceived threats. They can aim up to 30 to 40 cm with accuracy: "Anisomorpha discharges instantly in response to mild traumatic stimulation as, for example, when individual legs are pinched with forceps, or when the body is tapped or persistently prodded . . . Marksmanship is precise: the spray invariably drenches the particular instrument used for stimulation." Although most discharges required actual physical contact, Eisner (1965) found that the stick insects often would discharge at birds before being contacted by the bird. In trials, Eisner (1965) found the secretion to be an effective defense against ants, beetles, mice and birds; mouse- opossums (Marmosa sp.), however, managed to withstand the spray and consume the stick insect once its reservoir was depleted after up to five discharges from the larger females. One to two weeks are required to replenish the depleted reservoirs (Eisner 1965). Carlberg (1985) found that rats (Rattus norvegicus (Berkenhout)) initially were repelled, but some individuals managed to overcome the defense in subsequent attacks.
Although Gray (1835) mentioned the defensive secretion of A. buprestoides, the first account of its effect on humans that could be located was by Stewart (1937), who wrote about an incident in Texas: "The victim was observing a pair of Anisomorpha buprestoides . . . with his face within two feet of the insects, when he received the discharge in his left eye. . . The pain in his left eye was immediately excruciating; being reported to be as severe as if it had been caused by molten lead. Quick, thorough drenching with cool water allayed the burning agony to a dull aching pain. The pain eased considerably within the course of a few hours. Upon awakening the next morning the entire cornea was almost a brilliant scarlet in color and the eye was so sensitive to light and pressure for the next forty-eight hours that the patient was incapacitated for work. Vision was impaired for about five days." Symptoms gradually disappeared and there were no lasting effects. Albert (1947) described a similar but less severe incident.
Recent accounts (Dziedzyc 1992, Hatch et al. 1993, Paysse et al. 2001) report incidents with essentially similar symptoms, the first and most severe involving a dog. In that case, the dog suffered an ulcerated cornea, although the damage could have been self-inflicted after the encounter with the stick insect (Dziedzyc 1992). The recommended treatment includes immediate irrigation of the eye with large amounts of water, followed by administration of over-the-counter analgesics if needed for pain. Medical attention should be sought if more severe symptoms, such as decreased vision or light sensitivity, are present.
