Northern stick insects (Diapheromera femorata) are one of the most common insects I encounter walking through the shaded woodlands. In small patches I’ve been able to spot a dozen or more male nymphs congregating to feed, not counting the numerous others that evade my detection. Though we usually think of stick insects as shy and cryptic animals, competition for females is fierce. Because of high local abundances, males engage in extended pairings with females by clasping her abdomen tightly with modified hooked cerci. These pairings can last over five days in Diapheromera, but remarkably in other species pairings can last over two months at a time. This mating behavior serves to guard females from sperm competition, and males will physically strike and wrestle intruder males in attempts to dislodge the competitors.
Molting (ecdysis) is a risky and taxing process— pumping delicate soft tissues out of an old crinkly chitinous shell only to be left vulnerable to predation. Most diurnal arthropods perform this task at night, where their light fresh bodies are perhaps less conspicuous to predators. But the process doesn’t always go according to plan. “Mismolting” can occur when the arthropod gets stuck and fails to expand properly, resulting in a disfigured state which is often fatal. Finding mismolted animals in the field is uncommon, but it happens, and I’m always impressed to see just how much they can survive with a handicap. In flying insects any deformity whatsoever usually renders them incapable of performing the daily habits needed to sustain themselves, but in more sedentary and cryptic insects like this northern walkingstick, they can usually make it by. I have seen many mantids and phasmids with deformed legs and antennae, but this is only one of a few I’ve found with a curved thorax. Through subsequent molts, arthropods can actually regenerate lost limbs and correct deformed body parts. Given that the digestive tract has remained functional, this phasmid will probably make it to the next molting cycle where it will have another go at ecdysis.
