Friday Cat-erpillar Blogging: Seriously Disturbed

Smartweed Caterpillar

Smartweed Caterpillar

Caterpillars are adpated to rapid growth, development and continuous feeding. In the presence of predators, engaging in feeding behavior may attract predator attention and therefore not be adaptive. A group of Australian scientists* studied the behavior of gumleaf skeletonizer caterpillars, Uraba lugens, before and after “attacks”. The researchers “attacked” caterpillars by pinching them on the head or the abdomen, two or six times. In their experiment, the numbers of caterpillars that did not feed during the 3 hours after attack increased for the disturbed caterpillars compared to undisturbed controls. Caterpillars that were “attacked” six times were less likely to feed during the next 3 hours than those only attacked twice. The authors concluded that the caterpillars “assess the risk” of predation from and delay feeding to avoid predators.

*Petah A. Low, Clare McArthur, Dieter F. Hochuli.2014 Dealing with your past: experience of failed predation suppresses caterpillar feeding behaviour. Animal Behaviour 90:337e343

http://dx.doi.org/10.1016/j.anbehav.2014.02.020

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Species Identification

Halloween Pennant

Halloween Pennant

Insect taxonomists seek to delimit, describe and identify species. The tools of molecular biology can be useful in cases where species cannot be readily identified based on morphological characters. Some insects are only known from collected adults and have never been clearly associtated with an immature. The sure way to associate adults and immatures is to rear the insects from eggs and describe the immature stages. For many insects, especially many aquatic insects, eggs are difficult to obtain and immatures are difficult to rear. Adult hymenopteran parasitoids may be captured in traps but the host unknown. This complicates the process of linking adults and immatures. Immatures of some species may have multiple forms or be nondescript. Scale insect immatures start life as mobile “crawlers” but settle onto plants and secrete a waxy covering. In some cases, including agricultural pests, the scale insects cannot be identified in the immature stage. Identification requires waiting until adults emerge and identifying the adults.

DNA markers are proving useful tools in many otherwise intractible cases. A species has the same chromosomes, genes and DNA sequences as an adult as it does as an immature. A DNA sequence that is diagnostic of an adult insect is diagnostic for all stages of immatures as well. DNA markers are useful for linking immatures and adults and can speed the process of identification.

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Insects in Spittle

Spittle bug

Spittle bug

Spittle bugs (Cercopidae) produce a frothy spittle that can give protection from predators and parasitoids. Small insects may become trapped in the spittle or potentially use it as food. J.B. Whittaker* collected the spittle from over 1300 spittle bugs of two cercopid species and found 158 invertebrates, most probably trapped in the liquid. The most numerous were moth flies (Psychodidae), other small flies, springtails and mites constituting two thirds of individuals collected. Smaller numbers of springtails, tiny wasps, thrips, other homoptera, spiders and even two tiny caterpillars were found in spittle.

Whittaker, J.B. 1970. Cercopidspittleas a microhabitat. Oikos 21:59-64.

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Relapsing Fever

Body louse

Body louse

One of the diseases that is transmitted by the body louse is relapsing fever. Beginning in the late 1800s, biting insects were shown to be capable of human disease transmission. An outbreak of relapsing fever at a mission school near Bombay, India in 1907 was investigated by an army medical officer, Percival Mackie*. Mackie noted that the relapsing fever quickly spread through the boys dormitory. He also noted that the boys were infested with many body lice. The girls and the girls dormitory had few body lice. The epidemic spread slowly to the girls dormitory, appearing first in girls who and aided nurses in the boys dormitory. The increase in relapsing fever in the girls dorm was accompanied by an increase in body lice. Mackie examined body lice collected from the dorms and found clear evidence of spirilla in the lice. Mackie concluded, “…the above facts are sufficient to throw grave suspicion on the body louse as a transmitter of relapsing fever.”

Relapsing fever is called “yellow plague” as it can damage the liver and produce a yellow skin tone. It is associated with war and poor sanitary conditions for civilian refugees. During WWI, a half million Serbian people contracted relapsing fever. A short period later, from 1919 to 1923, war in Russia and Eastern Europe led to massive outbreaks; 13 million cases that left 5 million dead. Today, outbreaks can be managed by lice control through pesticide use. Prevention of war and refugee crises is preferable.

* Percival Mackie. 1907. THE PART PLAYED BY PEDICULUS CORPORIS IN THE TRANSMISSION OF RELAPSING FEVER. British Medical Journal. pp 1706-1709

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Lice History

The relationship between lice and Homidae

The relationship between lice and Homidae Image: Boutellis &c

Obligate parasites attached to a single host species will adapt to the host and form new species as its host forms new species. The evolutionary history can be traced through the changes in the DNA sequences of the genes. Boutellis and colleagues* review the history of lice in humans and our closest relatives. Humans have two species of lice; Pthirus pubis, the crab or pubic louse and Pediculus humanus, the head and body louse. Lice in the genus Pthirus diverged from the genus Pediculus over 13 million years ago on a common ancestor of gorillas, chimpanzees and humans. The lineage leading to gorillas lost the lice genus, Pediculus after it had diverged from the lineage leading to humans and chimpanzees, but retained lice of the genus Pthirus. Modern gorillas may be infested with Pthirus gorillae, which resembles the human crab louse.

The lineage leading to Humans and chimpanzees lost the lice genus, Pthirus. The genus Pediculus diverged in tandem with the split in the chimpanzee and human lineages about 6 million years ago. Modern chimapanzees may be infested with a relative of the human head lice, Pediculus schaeffi. Sometime after the split in the lineages of chimpanzees and humans, a little more than 3 million years ago, the human lineage reaquired Pthirus, through contact with gorillas. In the current state of affairs, gorillas have only the genus, Pthirus, chimpanzees only the genus, Pediculus and humans have both Pediculus and Pthirus.

*Amina Boutellis, Laurent Abi-Rached, Didier Raoult. 2014. The origin and distribution of human lice in the world. Infection, Genetics and Evolution: Volume 23, April 2014, Pages 209-217.

http://dx.doi.org/10.1016/j.meegid.2014.01.017.

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Better Head Lice Management

Head Lice Cartoon

Head Lice Cartoon from BusinessWeek
Illustration: Kelsey Dake

Head lice is a public health issue and requires participation from the public to be effective. If all groups are engaged in checking and eliminating head lice, then the public will experience reduction in risk of infestation. The most effective transmission of head lice occurs from direct head to head contact. Schools can be a significant site of transmission from family to family. A group of Norwegian scientists* surveyed practices among schools, ethnic and socioeconomic groups in Norway. They found differences in the responses among the groups.

They found that prior experience to head lice was correlated with more frequent inspection for lice. However, the frequency of checking was noted to have declined 1 year after an infestation. Immigrants from countries where lice are more prevalent inspected more frequently. However, they were less likely to notify authorities and more likely to purchase peduclicides (lice pesticides) than native Norwegians.

The scientists made several recommendations for a lice reduction program. Most important is early detection and elimination. Cases of lice infestation in schools should be immediately communicated to the community and more frequent inspections made. They recommended written and video communication at the start of school to emphasize the need to frequently inspect for lice (monthly) targeted at natives, and the advantages of reporting targeted especially to immigrants. The information should inform parents of the best practices and encourage rational rather than emotional responses to the problem. In their words “unnecessary negative emotions” are counterproductive. They inhibit communication in times of increased risk, discourge seeking help and advice from lice experts and in some cases result in children missing a large number instructional days. They suggest making available pest control advice to families that are affected by lice so families can avoid excess cleaning that is ineffective, reduce their workload and use the most effective means of lice control.

Western culture is gradually breaking the taboos about health issues communication. US First Lady, Betty Ford talked openly about her breast cancer and broke the silence around this important health issue. The US was forced to become more open about a number of health issues in order to combat the AIDS epidemic. Lack of open communication at the start of the epidemic led to worse results. Parasites, including insects, are a public health issue. Head lice is another public health issue that could benefit from more open discussion.

*Bjørn Arne Rukke, Arnulf Soleng, Heidi Heggen Lindstedt, Preben Ottesen & Tone Birkemoe. 2014. Socioeconomic status, family background and other key factors influence the management of head lice in Norway. Parasitology Research.
DOI 10.1007/s00436-014-3833-9

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A Lousy Problem

Head Lice.  Photo: John Clark, UMass

Head Lice.
Photo: John Clark, UMass

In the United States today, most people are free of head lice. That has not been true for most people in human history. The keys to a lice free society are effective lice treatments used in conjunction with prompt detection and steps to eliminate a lice infection. Many schools use quarantines, banning children with lice infestations from returning to school until lice are eliminated.

Recently, the use of quarantines has been questioned. Theoretically, quarantines could be effective lice control. In reality, they are not because school children rarely get the prolonged close contact necessary for transmission. Quarantines do not substantially improve the effectiveness of other control measures.

Health organizations no longer promote quarantines. Children may be harmed by missing school due to improper diagnosis. School nurses and other officials sometimes misidentify dirt and debris in the hair as lice eggs. Many lice treatments will kill all the active lice but not kill lice in the egg stage. The survivors are killed with a subsequent treatment after the eggs hatch. In the meantime, the child may still have some nits, but is unlikely to spread lice to others.

The Broward County School District near Miami Florida changed their lice policy based on scientific evidence. Children with lice would require treatment, but not be sent home from school. This policy ignited a storm of protest from parents. This is understandable. Lice cause revusion and can be difficult to elimate. Parents don’t want to take a chance that their children might get lice. Then they would have a big job (not so fun) of eliminating lice. In response to parental protest, Broward County reversed its lice policy. It will be interesting to compare rates of lice infestation between districts that use quarantine and those that do not.

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