Insects engage in a broad range of approaches to attracting and courting a potential mate. There’s singing, gift giving, caressing, and even dancing! While we can’t attribute human emotions like LOVE to wildlife, we do know that the primary purpose of most adult-phase insects is to reproduce, and mate selection is key to species survival.
Let’s start by clearing away any preconceived notions about courtship in insects. First, most insect (and arachnid) species have both males and females that must mate to reproduce. They have to find each other. Then they need to make sure they are the same species. From there, mate selection (or rejection) may be involved. Courtship helps with the selection process. Either the male or the female can lead all or part of the mating ritual’s steps (attraction, courtship, and even the mate selection decision), depending on the species. When there is an abundance of males, she may pick the one with the best traits for her offspring. Or, the males may fight each other to prove their worth. Or the males may hold a singing competition! Or a rejected male may try again by offering a larger gift!
This male beetle’s antennae help him find a mate by detecting her pheromones.
Attraction Methods
Attraction methods are about how males and females find each other. It’s pretty remarkable that tiny insects can find mates across long or short distances—while we don’t even see them! Methods include using species-specific pheromones, visual displays, and acoustic signals.
Pheromones are chemicals that are usually released by the female. They become airborne as a call of readiness to mate. A male insect can detect the pheromone from a female of his species, sometimes from great distances expanded by wind transport, using olfactory organs such as on antennal plumes.
Lightning bugs (they are really beetles) may be our most renowned example using visual display. Mates find each other using a species-unique bioluminescent signal that can vary by patterns of pulses, color, duration of the overall display, time of night or season, and flight pattern. Males patrol by flying about while flashing. The female is stationary in low vegetation and flashes a response if she’s interested. They begin a flashing “dialogue” that can continue for some time. Stronger flashing males are usually more successful. New research is showing that pheromones may be involved in lightning bug attraction too.
Acoustic signals include our sounds of summer. Cicada, grasshopper, cricket, and katydid males’ songs fill the air during days and evenings until a hard frost. These songs are accomplished by rubbing body parts and amplifying that sound on their bodies, or by using plants. It’s up to her to select and approach him. Broad-winged Tree Cricket males rub their forewings to create a prolonged trill, amplified by using twigs or leaves. Humans can hear his loud trill 200 feet or more away.
Other acoustic signals defy human hearing. Tree hoppers are tiny little insects that can communicate with each other with sounds made using the stems and vascular system of their host plant. Courtship duets between the male and female are just one type of the communication purposes of tree hoppers.
The light area on the abdomen of lightning bugs is their “lantern” for signal flashing.
These Two-marked Treehoppers may be singing a duet through the stem.
Courtship Rituals
Courtship rituals are next, and are about mate selection. They include serenades, dances, giving of nuptial gifts, and physical touching.
Nuptial gifts come in different forms, but typically involve the male providing a nutrient-rich food that keeps her preoccupied during mating and supports egg laying. Dance Flies are a family demonstrating a range of approaches that varies by species. Courtship often involves a swarm of males “dancing.” The female selects a mate from the swarm, usually based on the size of the prey he’s carrying to demonstrate the worthiness of his genes. One species of Dance Fly has evolved to carry a nuptial gift wrapped in silk that looks like a balloon. However, many of the “balloons” are empty! Other species offer inedible objects. Still another Dance Fly species switches things around, with the females doing the swarming and competing against other females by inflating body ornamentation, while the males make the mate selection.
The male Dance Fly is at top, coupled with the female in the middle. She’s feeding on her nuptial gift (a March fly) at bottom.
The male Broad-winged Tree Cricket is a master of seduction, bringing many of the courtship approaches together. After he has attracted her with his singing, she climbs onto his back and they physically touch their antennae to confirm their species and intent. Then he raises his wings, exposing a gland with a highly desirable secretion. This “honey pot” nuptial gift attracts and entices her into a position to keep her occupied. Next, he places a spermatophore, which is a protein capsule containing sperm, onto her body for sperm transfer. She’ll eventually eat the capsule, but he needs to keep her occupied so she leaves it alone until the transfer is complete.
These Broad-winged Tree Crickets are in the final stage of their ritual where he has exposed his “honey pot” and the spermatophore (upper right) is in place.
My all-time favorite courtship belongs to a tiny fruit fly, Euaresta festiva, that has no common name. Their courtship takes place on Giant Ragweed, their host plant, during flowering. Achoo! Like many fly species, they move their wings from front to back singly, one side at a time. (Wing movement may produce sounds of serenade too.) But their amazing dances go beyond those of other flies. They do a distinctive dance shaking their wings and booty as they chase each other around the plant, and will also face each other and lock their mouth parts while continuing the wing movement. Such fun!
Tiny fruit flies locked in a “kissing” display waving their wings, and a pair dancing.
Unfortunately, mating can be a dangerous activity, particularly for some predator species. Females are often significantly larger than males and can be the physical aggressor. For mating to take place, the male needs to not only convince her of his worthiness, but make sure she doesn’t decide to eat him! Some Araneus species spider males like the Marbled Orbweaver are strictly nomads, searching for females (with the aid of her pheromones). When he finds her, one approach is to spin a “mating thread” across her web and attempt to calm her by plucking it. He’ll test her intent by caressing her legs. Failure can result in his death.
The Marbled Orbweaver male (left) touched her legs cautiously on several approaches. She appeared calm, but then—he was GONE! I found him hanging on a silk lifeline just above the ground, having made a life-saving escape. She went back to her retreat.
Post-mating Behaviors
There are a few post-mating behaviors to note. Males sometimes “mate guard.” For example, when damselflies mate, the male connects to the female with a “lock” that is unique to the species. A damselfly male of the Dancer genus often remains connected until she lays her eggs (oviposits) to guard against male rivals, thereby ensuring his progeny. This guarding behavior also helps protect her from predation. I have observed these males pull females away from water striders and out of spider webs.
Lastly, on a morbid note, some females cannibalize their accepted mates. While this seems horrifying, his life purpose is now complete, and his sacrifice provides her nourishment to support egg laying.
Dancer damselfly males remain attached to the female throughout her laying of eggs.
This female cabbage butterfly’s position on the ground denotes rejection. She may have already mated or not been interested in this male.
This non-native Chinese Mantid has eaten the head and upper body of her mate (upper left).
Conservation of Insects
We know insect populations are in serious decline. The primary reasons are usually attributed to the same ones as birds and other wildlife – habitat loss and degradation, pesticide use, invasive species including disease, and climate change. As we learn more about insect courtship, it’s easier to appreciate how pollution also obstructs insect reproduction and so contributes to insect decline.
- Light pollution obliterates dark evening skies for visual displays and navigation to find mates,
- Particulate matter and specific air pollutants can mask chemical communication, and
- Noise pollution destroys acoustic signals and sound communications.
You can do your part by keeping the sky dark at your home and in your community. Check out our previous articles on reducing outdoor lighting and reducing noise pollution for ideas on what you can do. Insects and arachnids may not feel love the way we do, but we certainly can show love towards them!
Karen Campbell, a member of Lehigh Valley Audubon, PA Master Naturalist and Certified Pollinator Steward, provided the content and images for this article. Follow Karen on Instagram @kareninnature or visit her website at focusonnatives.com.