Kingdom Animalia Order Coleoptera Family Meloidae Higher classification Darkling beetle | Phylum Arthropoda Suborder Polyphaga Subfamily Meloinae Rank Species | |
Similar Beetle, Insect, Lytta magister, Cysteodemus armatus, Arthropod | ||
The Iron Cross Beetle is a species of blister beetle that is often detrimental to humans and their livestock and is in general a pest. They do not deliberately harm humans but they usually venture in alfalfa fields. The beetle is dangerous to eat because it contains high amount of cantharidin toxins.
Contents
Etymology
Word History: The genus Tegrodera was named by Le Conte in 1851 (Blaisdell SR., Frank E.). The species name T. aloga was coined by Skinner in 1903.
Distribution
Iron cross beetles live all over the world except in New Zealand and Antarctica. There are more than 300 blister beetle species in the continental United States. New Mexico has at least 28 species in eight genera, including some found in alfalfa. Some blister beetle species are gregarious, congregating in large numbers, especially near field margins. Livestock poisoning cases are probably a result of baling parts of these swarms into alfalfa hay. It is unlikely that individual beetles will fatally poison livestock [1].
Although the larvae of blister beetles parasitize bees or feed on egg masses of other insects such as grasshoppers, adult blister beetles feed principally on various plant flowers and foliage. As the beetles’ primary weedy hosts mature and dry, beetles can enter lush alfalfa fields. Data from New Mexico State University Cooperative Extension Service indicate blister beetles are found sporadically in alfalfa from June through August, usually in low numbers. However, blister beetle swarms have been reported in isolated alfalfa fields in several counties in New Mexico as early as May and as late as October, requiring constant grower vigilance. [2].
Description
The Iron Cross beetle is generally about 2 cm long; it has a long, narrow and cylindrical body and a wide head. The beetle is easily recognizable due to its contrasting yellow and red spots found on its black body. The brightness of the spots is due to the cantharidin toxins the beetle carries; this coloration is known as aposematism, and it works as a warning signal to protect itself from predators. It is more common to find these beetles in larger groups rather than individually.
Behavior
A few adults are nocturnal, but most are diurnal or show no cycle. Since adults are gregarious (socioable) and often highly colored, they tend to be conspicuous.The iron cross beetle love palo verde trees and they usually lay their eggs at the base of the flower buds. The eggs then lend to hatch when the flower bud opens. They pupate in the nest and emerge as adults the next spring. [3]. The iron cross beetle like most beetles have sexual reproduction. The species is very gender-scripted, with the male fighting to mate the female. Eggs are laid by the female in protected areas like under stones.
Diet
Iron Cross beetles eat mostly flowers and some vegetables. They also eat the leaves of some plants, as well as tomatoes, clover, alfalfa, potatoes, beans and peas. It is also said that some of the larvae eat grasshopper eggs.
Relationship to Humans and Livestock
The Iron Cross beetle Tegrodera aloga (also known as blister beetle or soldier beetle) is more harmful to humans than helpful. This is primarily due to a poisonous chemical called cantharidin. Cantharidin is one of the most widely known natural products of insects; in the Iron Cross beetle it is excreted through the leg joints and/or the antennal pores. (Ghoneim, Karem S.) It has drawn a lot of attention due to its toxicity to humans and the painful/fatal diseases it inflicts upon certain livestock. This chemical, C10H12O4, causes severe skin blisters (dermatosis) to humans within hours of exposure to it; it is not known how much of this substance it takes to cause a skin blister. The insect secretes this substance as a defense mechanism, or it can happen if it is crushed and comes in contact with skin. (Ghoneim, Karem S.)
Cantharidin is a poisonous substance which can prove fatal to humans if ingested. The lethal dose for humans when ingested is 10 mg,or 0.5 mg/kg of a human’s body weight. The main concern revolves around when the beetle is ingested by livestock, in particular horses. (Pinto, John D.) The lethal dose for horses in regard to their body weight is 1 mg/kg which sounds like a better case than for humans, but the horses have a higher chance of actually ingesting the beetles since they are known to be found in horses’ food, especially alfalfa. “Potential New Insect Pests of Forage Crops in California,” by Charles G. Summers, states that these beetles are starting to pose a problem for farmers in California due to them being “killed during harvest and incorporated into baled hay, or indirectly by transfer of the hemolymph [blood of the beetles] from crushed beetles onto forage.”
On the other hand, this beetle is also considered beneficial because cantharidin is used in the medical field as a topical medication in the removal of warts, removal of tattoos, and has even been looked into for certain cancer treatments. (Chao, Zhang, Peng Yi, Wang Fengchao, Tan Xu, and Liu Nan) Its use in the treatment of removing warts has been common for many years, and is still used by dermatologists (skin doctors).