Glow-Worms' Population is Dimming
Fri, December 9, 2022

Glow-Worms' Population is Dimming


A new study published in the journal Insect Conservation and Diversity reveals that the population of glow-worm has been dimming since 2001. A glow-worm is a luminous insect larva that emits light from its abdomen to warn-off predators, attract prey, or attract mates.

The research highlights that the climate crisis is a clear factor in why there has been a plunge in glow-worm numbers. According to The Wildlife Trusts, a movement of people that gather together to make a positive difference for wildlife and future generations, glow-worms are not worms but a beetle. The males look like the typical beetles but it is the female glow-worms that light up to attract their mate in the darkness of their grassland habitats. They are usually found in parts of England, such as Wales and lowland Scotland. The Wildlife Trusts is not a part of the recent study.

Non-departmental public body Environment Agency’s Tim Gardiner, who led the research, said via world news provider The Guardian that the population of glow-worms has been declining for decades now but no single hard evidence has just been presented. This led them to conduct the study on the long-term changes in the insect’s population. Gardiner went on to say that a big decline of glow-worms’ population is observed in several sites in Essex, a county in Southeast England.

The team shared that they used the data gathered by citizen scientists during their nighttime walks between June and August every year. When these scientists go out, they only record finding one or two glow-worms. Changes in the weather accounted for the glow-worm population decline. Gardiner said that if their number already declined in the last 18 years, there is a possibility of more local “extinctions” in the next 18 years.



Importance of insects

Insects offer useful services to the environment and mankind in general in various ways. For example, they help pollinate crops that people rely on as food and insects also act as sanitation experts by cleaning up some waste in the world. Experts from different countries have also previously said that the fates of insects and humans are intertwined. They warned the public that the insect extinction crisis is worrisome to mankind that solutions should be made immediately. The decline of their population would mean a loss of irreplaceable and essential services to humanity. Their paper has also noted that the British butterflies are “fast disappearing.”

Gardiner and colleagues said that there was a 75% fall in the population of glow-worms since 2001. “Wouldn’t it be sad if there weren’t these things anymore?" Gardiner said. He recalls that the first time he saw glow-worms, the moment was “magical” and he still gets excited to see the insect glow every summer. In the United States, the population of Poweshiek skipperling butterfly has also shrunk dramatically. In a total of 217 sites, where the butterfly was historically seen, their population declined rapidly since 1872 as their habitat was destroyed. Now, the butterfly is extinct.



Insect: statistics

The world’s largest museum and research complex, the Smithsonian Institution, said that there are about 900,000 different kinds of living insects that are known in the world and it is a representation of about 80% of the world’s species. According to studies conducted by Terry Erwin of Smithsonian Institution’s Department of Entomology in Latin America, there are now 30 million species of insects living and there are some 10 quintillion individual insects that are alive.

In the US, there are about 91,000 described species and some 73,000 undescribed species of insects. The largest numbers of described insect species in the US include Lepidoptera (moths and butterflies) at 11,500, Hymenoptera (ants, bees, wasps) at 17,500, Diptera (flies) at 19,600, and Coleoptera (beetles) at 23,700.

There are social insects that come in large numbers in their nests. For instance, an ant nest found in Jamaica contained about 630,000 individuals. Locust swarms can hold up to one billion of their species. Several factors create these numbers of insect species and individuals, such as their capacity of a flight, small size that enables survival in different habitats, their long geological history, their general adaptive abilities to the environment, and their ability to store sperm for delayed fertilization. Insects have remarkable reproductive and fertility abilities, which led to their vast numbers.



Fireflies and glow-worms

There are about 2,000 species of fireflies and glow-worms. Although both fireflies and glow-worms belong to a group of luminous beetles, their only difference lies in their wings. Fireflies are the winged forms, so they are capable of flight. Glow-worms are wingless, thus the flightless members of their insect family. Each adult female glow-worm lives only for a few weeks until she mates and then dies soon after she lays her 75 to 100 eggs in the ground. The eggs will then hatch into larvae in a few weeks and that larva will remain as such for one or two summers. Glow-worms, although not yet considered an endangered species, are already declining in population for unexpected and expected causes. The increased use of night lighting and the destruction of wetlands impact their population and reproduction activities. Fewer flying males (lighting bugs) and wingless females (glow-worms) are also observed in suburban and urban settings. The unnecessary use of pesticides in suburban areas also impacts their population.

Michael C.R. Alavanja, Dr.P.H., who was not involved in the study, shared in research that approximately 1.8 billion people engage in agriculture worldwide and most of them use pesticides to protect the commercial products and food they produce. Over 1 billion pounds of pesticides are used in the US every year and 5.6 billion pounds worldwide.

Database company Statista shares the following percentages of decline in selected global insect populations in the past decade: caddisflies (68%), butterflies (53%), beetles (49%), bees (46%), mayflies (37%), dragonflies (37%), stoneflies (35%), and flies (25%).

People can help glow-worms by practicing careful grazing, land and garden clearance, and hay-cutting at the right time. These things keep grasslands in good condition to make it a good habitat for glow-worms. Educating the public on the importance of glow-worm conservation also helps protect their colonies. Increasing academic knowledge on glow-worm species is also encouraged.