Complaints by workers at a food-processing plant of “invisible insects” led to the discovery of an infestation of springtails.
Here in southwest Michigan we have — most of the time — a fairly consistent layer of snow from December through mid-March. Our days, like the rest of the United States, grow longer after December 21 of each year. With increased sunlight, the ambient temperature of exposed surfaces such as homes, driveways, other structures and even our blanket of snow rises. Increasing the temperatures even more is the dust, dirt and airborne “stuff” that lands on the snow. Since these substances are usually darker in nature, they absorb more UV light and heat.
This brings us to springtails. These extremely small (1/32 to 1/8 inch) insects get their names from the species’ furcula/spring-like appendage that allows them to jump. They’re mostly considered to be a pest of nuisance value only, and are attracted to areas of high moisture. They have a simple metamorphosis and are usually white or gray in color. These insects are the source of the term “snow flea,” due to the fact that they can jump, withstand colder temperatures and will invade structures simply to get warm.
Their development time (egg to adult) usually requires two t three months, but it varies greatly with species and temperature — it can range from one week to more than two years.
They feed on decaying vegetation, fungi, bacteria, pollen, algae, lichens, arthropod feces, and carrion. They often invade structures in search of moisture when their natural habitat dries up. Areas of high moisture such as bathrooms, crawlspaces and areas where leaking water has not been addressed and corrected are common areas of infestation. Overwatered house plants, as well as plantscapes and water features in office buildings, are also areas of concern.
Control is usually accomplished by drying up areas of infestation and or removing objects that are moist.
They do not bite or transmit diseases although Entomobrya nivalis has been reported as causing an itching type of dermatitis in humans. Currently there is no accurate scientific evidence that supports that these insects can cause dermatitis or other actual medical concerns. There are reports that delusions of parasitosis (DOP) cases are on the rise, probably due to the resurgence of bed bugs, and care must be taken to positively identify probable sources and causes of these types of issues and concerns.
A Springtail Problem.
Near the end of February a few years ago, a customer called with the report of invisible, biting insects in its warehouse. Initially, before an inspection, it was theorized that the probable cause was dry skin, or some other environmental issue — not very likely pest-oriented. The warehouse in question was owned and operated by a dry food manufacturer. Dried food products and the boxes, pallets, skids and other supplies needed in such a facility were all present. The facility’s pest management program abided by the audits of both Siliker and AIB, so all monitors, insect light traps and other devices were in place. As well, a review of the electronic reporting showed no unusual findings or any reports.
An inspection was scheduled for a supervisor to go with a service technician to see what was going on.
Several warehouse employees complained of bites that were always on bare skin, and not underneath clothing. The warehouse was in good condition — floors were cleaned regularly, no litter or clutter was noted. Lighting was adequate, spacing of products was good and HVAC systems were in good shape.
This warehouse was about 500,000 square feet, constructed with block wall, poured and polished concrete floors and a flat top, or slightly canted aluminum roof with appropriate gutter lines and drainage lines.
The initial inspection turned up no insect or arthropod pests in any of the areas inspected. No evidence of a rodent or other mammal population was found (to help rule out the possibility of fleas). Locker rooms, break rooms, offices, warehouse offices and the general floor space were among the areas inspected at the time.
Sticky boards — some left uncovered and some in cardboard stations — were placed throughout the facility. This warehouse, belonging to a food processor, had the requisite insect light traps in place and were being serviced. No pests were found in the ILTs at this time. The target date to inspect these monitors was 10 to 14 days after the placement.
Over the next two weeks, our weather was unseasonably sunny although not quite warm — temperatures remained around 40°F.
Our return visit showed dust and miscellaneous debris but no signs of insects or other arthropods, such as spiders, on the monitors. These monitors were examined under the microscope.
Further monitoring was put into place at this time and another inspection date set. A team consisting of myself, a supervisor and the quality assurance leader for the customer was involved this time. During our inspection, it was noted that in two areas near the middle of warehouse areas, there appeared to be a stain of some sort on the floor. No employee had any idea about the issue, so we turned to the company’s internal records.
It turned out that several of the workers had noted a slow leak from the ceiling and had been vacuuming up the water as it dripped. They had indeed turned this in to the maintenance department for investigation. Since, however, the roof was covered with ice and snow, it was decided that the inspection of the roof was to be postponed until the dangerous conditions subsided and a worker could safely inspect the roof and take appropriate measures.
A final inspection found that in both areas where the stains were found, the expansion joints and the absorptive material used in those joints was moist, with a reading of around 75 percent humidity. Using a small vacuum kit for collecting insects, several yards of this crack were vacuumed — there we found the springtails.
These insects were identified using the key found in the Mallis Handbook of Pest Control as Entomobrya sp. It was noted that further away from the stains, the numbers of springtails decreased dramatically. From about 50 feet, the insects were not present at all.
During an inspection of the roof, we found debris and ice caused standing water to accumulate directly over the area where the stains were found inside the building. It was theorized that the insects were simply drawn through the leak by the water through the leak, fell to the floor and migrated to the moist expansion joints. A temporary fix to the leak on the ceiling dried up the water source and the removal of the damaged caulking material virtually eliminated the insect population within a few days. Subsequent monitoring over the next several weeks showed no further presence of insects.
The moral of the story is this: Always think outside the box and never go in with blinders on. During the ongoing training of technicians, supervisors and inspectors sessions should always include the lesson of going across the street to look at the “whole picture,” not just the sites of infestation.
References: NPMA Field Guide to Structural Pests; Mallis, Ninth edition; Goddard, Arthropods of Medical Importance.
The author is director of sales for Rose Pest Solutions in Chicago. He can be reached at firstname.lastname@example.org.