Katydids are large, typically green insects belonging to the order Orthoptera, closely related to grasshoppers and crickets. Often mistaken for their relatives, they are identified by their long antennae and leaf-like appearance, which serves as camouflage. Although their size and nocturnal habits sometimes cause concern, katydids pose no significant threat to human health or established garden ecosystems. Concerns usually center on physical interaction, potential plant damage, or the loud sounds they produce at night.
Threat to People and Pets
Katydids possess strong mandibles, which are the chewing mouthparts typical of herbivorous insects. These mouthparts are designed to process plant matter, not to inflict injury on large animals like humans or pets. A katydid will only attempt to bite if it feels trapped or is mishandled, and this action is purely reflexive.
When a bite does occur, it registers as a harmless pinch that does not typically break the skin or require medical attention. Katydids do not carry venom, making the interaction non-toxic. The concern for people is usually the startling sight of the large insect, not its physical capability to cause harm.
There is no evidence that katydids serve as vectors for diseases transmissible to humans or household pets. They do not feed on blood or waste, and their life cycle does not involve carrying pathogens of concern. If a pet eats a katydid, the insect is non-toxic and poses no internal threat.
Katydids as Garden Pests
Katydids are herbivores, utilizing their mandibles to consume soft plant tissues, including leaves, flowers, and the skin of developing fruits. Their feeding habits are sporadic and localized; they do not swarm or congregate in numbers sufficient to defoliate large areas rapidly. This contrasts sharply with true agricultural pests, such as locusts, which destroy entire fields overnight.
The most common sign of katydid feeding is irregular holes within the center of leaves or scalloping along the margins of the foliage. They favor the newest, softest growth where cell walls are less rigid. While this damage can be unsightly, it is cosmetic and does not compromise the health or long-term survival of a mature plant.
In fruit and vegetable gardens, katydids occasionally target ripening fruits, particularly those with thin skins, chewing shallow feeding pits. The injury often heals over, but resulting scars can enlarge into brownish, corky patches that distort the fruit’s appearance. However, their populations rarely reach outbreak levels in residential settings, meaning control measures are unnecessary and the damage is tolerable, as the internal quality of the fruit is unaffected.
Understanding the Noise
The loud, characteristic nocturnal sound associated with katydids is produced exclusively by males through stridulation. This sound is generated by rapidly rubbing a file-like structure on one forewing against a scraper on the other, creating the distinct, rhythmic “katy-did, katy-didn’t” call. The frequency and pattern of the call are species-specific.
The function of this acoustic display is reproductive, allowing males to attract females and establish spacing between competing individuals. While the volume can be high, reaching up to 98 decibels in some species, the noise represents zero physical threat. The sound is a form of communication that can become an annoyance, especially when an insect resides near a bedroom window during the summer.