Thrips: The Insects Hidden Within Dow Gardens

August 4, 2022

While walking through the winding paths of Dow Gardens, we, the interns from Michigan State University (MSU) St. Andrews research facility, were determined to find and record the wide diversity of pollen that surrounded us. What we didn’t realize when collecting samples, however, was that there was a hitchhiker we often brought with us. When examining the flowers we collected, on the petals and anthers there was a little traveler: an insect known as a thrips.

Thrips are an insect in the order Thysanoptera, the name originating from the Greek “Thysanos,” meaning fringe, and “Ptera,” meaning wings, referring to the long hears fringing their wings (very visible in the images). The word thrips can be used to describe both single and multiple insects—meaning, one of these is still called a thrips, not a thrip. Like most insects, their body structure consists of a head, thorax, and abdomen. The thrips head is host to antennae and two compound eyes, comprised of dozens of smaller ones, and three ocelli: simple eyes that detect basic shapes. The thorax, in the middle, is separated into three subsegments: prothorax, mesothorax, and metathorax. The first pair of legs is attached to the prothorax, the 2 pairs of wings are attached to mesothorax, and the last two pairs of legs are attached to the metathorax. You can see for yourself that the front pair of legs emanate from a different spot than the back pairs. The abdomen is the largest segment and handles much of the thrips’ major bodily functions (e. g. digestion and gas exchange). Adults have thin, hair-covered wings, whereas the pupae and larva do not. In our experience in the lab, these wings can sometimes be absent, giving the thrips a degree of uniqueness.

Highlight of a thrips’ head. Note the 2 compound eyes with 3 ocelli.

A close-up of a thrips’ abdomen showing good anatomical detail.

Their preferred sources of food include garden crops and fruits, but they will resort to flowers and foliage in a pinch. A thrips life lasts about 30 days, and in that time they hatch from eggs layed on a leaf, go through two instars (development checkpoints), become pupas and fast (do not eat), and become an adult. Adulthood lasts about 11 days, during which they spend their time eating, mating, and laying eggs. Thrips mostly reside on leaves and within flowers, being found on every continent except Antarctica, where even these resourceful little insects cannot survive.

After finding our first thrips, we were curious as to what other insects we would find. The answer turned out to be… more thrips! Out of a total of about 50 creatures that we found on our slides, 45 were thrips, and one was a mite attached to a thrips. Most of these thrips were still alive and moving. Our group is convinced that we found at least two different species of thrips because some had a different shape between their thorax and head. It appears that these small bugs rule the microscopic world of flowers within Dow Gardens.

A thrips with the side of a dime for reference.

While these little bugs may seem like a cute addition to a garden landscape, thrips are not necessarily beneficial insects. Despite their small size (all were under 2 mm), their impact can be felt across the garden in the health and well-being of plants and flowers. Thrips can be a problem for plants in many ways. They enjoy feasting upon parts of plants, including their leaves, pollen, fruit, and buds. The females of most species mainly feed on pollen, which explains why we found so many on our flowers. However, more concerning is the fact that they vector dozens of diseases, meaning that they pass on illnesses from one plant to the next. The most troublesome disease thrips carry is Tomato Spotted Wilt Virus. This virus turns tomatoes into a wilted, shriveled, sickly version of their original forms. Thrips are not always good guys, but they have some redeeming properties, including their ability to act as a pollinator. Thrips encounter multiple flowers in their lifetime, and though they do not possess hair like bees and butterflies, we have seen several with pollen grains attached to them.

Thankfully, thrips have not simply been allowed to roam in private and commercial gardens. Predators of thrips have been used to limit the number of thrips throughout their crops. These predators include such as the green lacewing larvae (Chrysoperla rufilabris), the pirate bug (Orius spp.), traditional pesticides, and mites released to parasitize them. We found two pirate bugs and a mite in various flowers we brought back to our lab. Additionally, there are some types of predatory thrips that can be used to limit the number of harmful thrips. These heroic double-crossers attack and kill thrips, limiting their populations to manageable proportions.

Our experience with thrips was an interesting surprise in parallel to the work we did with flowers and pollen. Each new thrips we found provided a sense of elation and discovery. Seeing two antennae wave at you through the microscope was quite unexpected. We even had them receive a name, examples include Leche and Johnson. Upon further research as to their impact, their presence began to be concerning. None the less, these discoveries were still important to understand the interactions that take place in the complex ecosystem that makes up Dow Gardens. So, the next time you happen to be strolling along the gorgeous trails, if you look more closely at the sweet-smelling flowers, check to see if one of these little imps are hidden among the petals.