Ladybugs have a pair of antennae, which they use to perceive scents. This can help them in finding mates and food and avoiding predators. Their antennae are attached to their head, and because there are two of them they can help the ladybug work out where a smell is coming from.
What is an antenna?
Antennae are fascinating appendages, though they may often be one of the last things we notice on an insect, colourful wings or large eyes being much more attention-grabbing. Antennae are sensory organs that are common to many, but not all, arthropods. Like crabs and lobsters, crustaceans actually have two sets of antennae, a short primary and a long secondary. However, some arthropod groups, such as spiders, don’t have any antennae at all. Arguably, the most famous for their antennae are the insects, from those amazing plume-like antennae on a moth to the hair-like antennae on a grasshopper. They come in all different shapes and sizes, depending on the purpose the insect has for them. A common use is to detect scents, but they can also be used to feel, sense humidity and heat, feel vibrations, navigate, and so much more. Even beyond their sensory perceptions, they can be used as part of mating rituals or to grasp onto objects.
All insects are made up of a head, thorax and abdomen, with the antennae being attached to the head. Although the form varies wildly between insects, all antennae have three essential parts, the scape, pedicel and flagellum. The scape is the part that attaches to the insect itself, sitting within a socket that allows it to have a full range of movement. This is the only part of the antenna with its own muscles, which enable it to move. In other types of arthropods, such as the two-pronged bristletails, the flagellum also have a muscular system. The pedicel is the next segment and contains a collection of sensory cells. The rest of the antenna is made up of sections of the flagellum. How many there are and how they look is highly variable.
There are around fifteen different types of insect antennae. It is mostly the flagellum that varies in look, with the scape and pedicel often remaining a fairly similar shape, though there are some exceptions. Some forms are very understated, like the thread-like ‘filiform’, whilst serrated and ‘moniliform’ (beaded) antennae are more interesting to look at. Perhaps the most spectacular are the ‘pectinate’ (comb-like) and ‘plumose’ (long haired) antennae typical of male moths and mosquitos. Even more simplistic forms of antennae can be eye-catching if they’re long enough, such as those of the aptly named longhorn beetles.
Antennae have a number of different sensory receptors on their surface, as well as fine hairs. These can pick up all kinds of chemical compounds, which can tell the insect where to find food, where there are mates, or even whether a breeze is blowing. Many species of ants set chemical trails for their companions to follow to indicate where they might find food or how to get home. How strong the chemical signal is will tell the insects how big a prize there might be at the end of it. In order to be able to get up close and personal to these signals or to other smells, ants are able to bend their antennae like an elbow. Male moths also famously follow scents, and moth catchers often use manufactured female pheromones to lure in the males for surveying or observation.
A ladybug’s antennae might not be the easiest things to spot, being much smaller than those of many other beetle species. Like all insects they have two antennae, these are situated in front of the eyes on the head. Although many people think the area immediately next to the elytra (wing casings) is the head, this is actually the pronotum, a part of the thorax. The ladybug’s head is much smaller and sits just in front of this. The pronotum helps to shield the head, and the ladybug can pull its head slightly underneath it for protection like a tortoise. The head itself is relatively small and contains the mandibles, eyes and antennae.
The ladybug’s antennae have eleven segments and are club-shaped, with the last few segments being significantly wider than the rest. Though there is slight variation in antennae between species, most antennae are roughly as wide as their pronotum, if pointing straight out and brown in colour. If looking at a photo of a ladybug, you may mistake their mandibles as their antennae at first, but these are much larger.
What do ladybug’s use their antennae for?
Like most insects, the ladybug’s antennae’s primary use is for a sense of smell. Smell is very important to a ladybug, in part because their eyesight isn’t that great. Ladybugs have small black compound eyes. A compound eye is made up of lots of smaller eyes, which together give the insect a much clearer picture. Like many animals, ladybugs see in black and white; however, unlike many animals, they don’t have the luxury of night-vision. This means that a ladybug is pretty much as blind as you or me when the lights go out. However, poor eyesight isn’t going to hold a ladybug back, not when they have their fantastic antennae.
Ladybugs, like all insects, do not communicate verbally. They’re also not that great at body language, given the restrictions of their exoskeleton. Therefore, the language of love is very much a signature scent rather than a sonnet or a ballad. In order to attract a mate, ladybugs release a hefty dose of pheromones to call in others from nearby. However, this doesn’t mean that you could be walking by a rose bush and get a sudden waft of a ladybug. The scents that most insects release are too subtle or minuscule for our noses to detect, yet luckily an insect’s antenna is much more sensitive. Once the antennae pick up the right chemicals, it will send an electric signal down to the ladybird’s brain, calling it to action. In fact, there’s a whole section of an insect’s brain devoted to its antennae, to interpreting signals and controlling their movements.
The wonderful thing about antennae is that, because they come in pairs, they can also help insects to detect where a scent is coming from, so they don’t just head off in any old direction. This is similar to our ears, which are placed on either side of our heads, and at slightly different heights to allow us to pinpoint where a sound is coming from. As well as searching for romance, the ladybug’s antennae are important for picking up chemicals given off by their prey. This helps them hone in on plants infested with aphids or other pests, rather than trying to spot the often well-camouflaged individuals by eye. Ladybugs will also often spend their winters somewhere dark and out of the way. Although their eyes aren’t good enough to see at night, their antennae can allow them to sense if there might be unwelcome visitors waiting for them in the dark. So though we might be most interested in the bright colours and patterns of our ladybug’s, a ladybug’s most vital and most exciting tool may well be its antennae.