Urban Knowledge Master

Isometrus maculatus (De Geer)

Lesser Brown Scorpion
Author Hosts Distribution Damage Biology Behavior Management References


Julian R. Yates III

Extension Urban Entomologist

College of Tropical Agriculture and Human Resources

University of Hawaii at Manoa


Insects, spiders, millipedes, small rodents


Tropical areas worldwide; in Hawaii reported from Oahu, Maui, and Hawaii.


The sting of the scorpion is situated at the tip of the "tail" and it is made up of a very sharp, curved tip attached to a bulbous organ containing the poison secreting gland and reservoir. The sting is injected into the flesh of the prey by means of a quick, spring-like flick of the "tail." The sting curves upward when the "tail" is extended but downward when the scorpion poses for attack or defense. The victim is struck quickly and repeatedly with the thrust of the sting being made forward over the scorpion's carapace. Muscular pressure forces the poison into the wound through two small openings near the sting tip. Since the poison is inoculated beneath the skin, first-aid treatment becomes difficult since the impervious skin renders surface application ineffective. While the poison of the non-deadly species of scorpions is local in effect and causes swelling and discoloration of the tissues in the area of the puncture, the poison of the deadly species circulates generally over the entire body of the victim. There will be intense pain at the site of the sting but very little inflammation or swelling.

Generally speaking, the medical importance of the species of scorpion is determined not by its size but by the potency of the venom and its habitat. As with most venomous animals, young children and debilitated persons suffer the most severe symptoms when stung. The non-neurotoxic sting of our sole Hawaiian scorpion species produces a severe pain and swelling at the site of the puncture although the swelling on occasions spread over a wide area. Muscle pain and nausea have also been reported but these symptoms usually disappear after 24 hours. In Hawaii, there have been no reported fatalities due to scorpion stings.


Scorpions are easily recognized by their crablike appearance and their long, fleshy five-segmented tail-like post abdomen which ends in a bulbous sac and a prominent sting. The pedipalps are greatly enlarged so it appears clawlike. The true jaws (chelicerae) are small and partly hidden from the top by the front portion of the carapace (hard covering of the thorax). These creatures also have four pairs of terminally clawed legs.

Scorpions have a long life. A life span of 3-5 years is normal for many species. The male and female scorpions go through a courtship similar to that of spiders. After mating is completed, the female often eats the male. Scorpions do not lay eggs; their young are born alive. After birth, the youngsters climb onto the back of the mother where they remain until the first molt. The immature scorpions are nourished by yolk material stored in their bodies. They do not eat the body of their mother as it was once commonly believed. However, scorpions are cannabilistic and will feed on other scorpion species, smaller individuals of their own species, and/or individuals of their own size which they may catch while in the process of molting or soon after when the exoskeleton is soft. The mother scorpion may at times feed on her own young.


Scorpions prefer to live in warm areas. They are nocturnal creatures. They hunt and feed during the night while they rest during the day, hiding beneath loose rocks, loose bark of fallen trees, boards, piles of lumber, floors of outbuildings, and debris. The areas in a home where scorpions are usually found are under the house and in the attic. They usually invade the attic by climbing between the wall partitions. They are also found in kitchens, washrooms, or bathrooms where water is available and during the daytime, they hide in closets, shoes, folded blankets, etc. Some species even bury themselves in sand or loose earth up to a period of 6 months without food and water. The scorpion feeds upon insects, spiders, millipedes, and even small rodents.



The scorpion hazard around homes can be minimized to a great extent by getting rid of favorable hiding places such as rubbish, boards, loose rocks, bricks, lumber, and other materials. Adobe brick dwellings such as found in the S.W. U.S. have cracks and crevices that will provide harboring spaces for scorpions. These creatures may hide deep in the recesses and actually go without food and water for as long as 6 months.

The placement of damp burlap or heavy cloth on the ground may induce the scorpions to congregate so they can then be readily destroyed. Cats are quite effective predators. Poultry such as ducks and chickens are also efficient predators but the latter are more apt to be stung, sometimes with fatal results.


Chemical treatment within the dwellings should consist of spot treatment of baseboards, under furniture, in crevices and closets, around plumbing or any other areas where the scorpions are observed. Attics, crawl spaces, and basements also should be sprayed. Outdoor structures (foundations, porches, etc.) that is in contact with the soil should be treated to a height of 2 feet above grade if possible.


Vector Control Branch. 1982. Vector control manual (Chapter XIII, G. Komatsu). Hawaii State Health Department, Honolulu.

Scorpions. Cooperative Extension Entomology Notes No. 12. Cooperative Extension Service, College of Tropical Agriculture and Human Resources, University of Hawaii






Back To:

Urban Menu

Knowledge Master Home

Pest Search