December | 2016 | Pest Control India

Beetle Fossil Nearly Doubles the Age of Known Parasites of Social Insects

When ancient insects first evolved eusocial behavior and began forming colonies, it didn’t take long, paleontologically speaking, for parasites of those resource-rich colonies to evolve, as well. A newly discovered ancient species of beetle found preserved in amber dates this apparent parasitic behavior to at least 98.8 million years ago.

In a paper published in Nature Communications this month, researchers from Kyushu University and Columbia University detail a new species of rove beetle, Mesosymbion compactus, found in a Burmese amber specimen housed at the American Museum of Natural History, that exhibits the hallmark traits of previously known parasitic beetles from the family Staphylinidae, subfamily Aleocharinae. These beetles have specialized to live inside the colonies of social insects such as ants or termites and often feed on eggs, larvae, and pupae in brood galleries.

As revealed through advanced imaging of the fossilized specimen, M. compactus, like modern aleocharines, has a teardrop-shaped body resembling a horseshoe crab, a head hidden below the pronotum when viewed from above, mandibles pointing rearward, and short, compact antennae. “Together, the suite of characters presented by Mesosymbion define an ecomorphology that has arisen numerous times in Aleocharinae, and suggests a non-integrated social parasite that was probably treated aggressively by its hosts, potentially targeting colonies as a brood predator,” the authors write. They also posit that M. compactus was a parasite of termites.

The M. compactus specimen comes from the very same amber deposit in Burma that provided the earliest known fossils of social termites, estimated to be 99 million years old. Previously, however, the earliest known social parasite was a rove beetle dated to approximately 52 million years ago (discovered by the same researchers), meaning M. compactus signifies a significantly earlier beginning to the evolution of parasitism of social insect colonies, placing it much closer to the rise of social insects themselves.

“Mesosymbion reveals that this adaptive versatility extends deep into the Mesozoic, when eusocial colonies presented novel niches for occupation that few other taxa were equivalently predisposed to fill. The notion of Mesozoic social parasitism by aleocharines implies that ant and termite societies were subject to exploitation during most of their evolution, including a long period when both social insect groups are inferred to have been rare and ecologically insignificant,” the authors write.

Source: Entomology Today

Ants communicate by mouth-to-mouth fluid exchange

The study from the University of Lausanne, Switzerland, suggests Florida carpenter ants can collectively influence their communities by shifting the cocktail of proteins, hormones and other small molecules that they pass mouth-to-mouth to one another and their young through a process called trophallaxis.

“Food is passed to every adult and developing ant by trophallaxis. This creates a network of interactions linking every member of the colony,” says senior author Laurent Keller, Professor in the Department of Ecology and Evolution.

“A lot of researchers consider trophallaxis only as a means of food-sharing,” adds Professor Richard Benton of the Center for Integrative Genomics, also a senior author of the study. “But trophallaxis occurs in other contexts, such as when an ant is reunited with a nest-mate after isolation. We therefore wanted to see if the fluid exchanged by trophallaxis contains molecules that allow ants to pass other chemical messages to each other, and not just food.”

To answer this question, the team, led by first author and postdoctoral researcher Dr Adria LeBoeuf, analysed fluid from pairs of ants engaged in trophallaxis. Surprisingly, they identified a large number of proteins that appear to be involved in regulating the growth of ants, along with high levels of juvenile hormone, an important regulator of insect development, reproduction, and behaviour.

To see what effect this hormone has on the growth of larvae fed by trophallaxis, the scientists added it to the food of larvae-rearing ants and discovered that the hormone made it twice as likely that the larvae would survive to reach adulthood.

“This indicates that juvenile hormone and other molecules transferred mouth-to-mouth over this social network could be used by the ants to collectively decide how their colony develops,” says LeBoeuf. “So, when the ants feed their larvae, they aren’t just feeding them food, they are casting quantitative ballots for their colony, administering different amounts of growth-promoting components to influence the next generation.

“The effects of juvenile hormone that we see are consistent with previous studies in other ants and in bees where larvae treated with an analogue of this hormone tend to develop into larger workers and even queens.”

Along with growth proteins and juvenile hormone, the team also identified small molecules and chemical signals in the carpenter ants’ trophallactic liquid that help them recognize their nest-mates. They demonstrated for the first time the presence of chemical cues in the fluid that are known to be important in providing ants with a colony-specific odour that allows them to distinguish family from non-family members.

“Overall, we show that liquid transmitted among ants contains much more than food and digestive enzymes,” adds LeBoeuf. “Our findings suggest that trophallaxis underlies a private communication channel that ants use to direct the development of their young, similar to milk in mammals.”

“More generally, this opens the possibility that the oral exchange of fluids, such as saliva, in other animals might also serve previously unsuspected roles.”

Source : ScienceDaily

Common insecticides are riskier than thought to predatory insects

Neonicotinoids — the most widely used class of insecticides — significantly reduce populations of predatory insects when used as seed coatings, according to researchers at Penn State. The team’s research challenges the previously held belief that neonicotinoid seed coatings have little to no effect on predatory insect populations. In fact, the work suggests that neonicotinoids reduce populations of insect predators as much as broadcast applications of commonly used pyrethroid insecticides.

“Predatory insects contribute billions of dollars a year to agriculture through the elimination of crop pest insects,” said Margaret Douglas, postdoctoral researcher in entomology, Penn State. “We have found that neonicotinoid seed coatings reduce populations of these natural enemies 10 to 20 percent.”

According to John Tooker, associate professor of entomology, Penn State, the use of neonicotinoids has risen dramatically in recent years, especially for large-acreage crop species like corn, soybeans and cotton. The insecticide is most often applied to seeds as a prophylactic coating. When the seeds are planted, the insecticide enters the soil where some of it is taken up by plant roots. The chemical then runs systemically through the plant, protecting young seedlings from insect pests.

“Applying insecticides to seeds rather than broadcasting them across a field was thought to reduce unwanted effects on natural enemies,” said Douglas. “But we found that seeds treated with neonicotinoid insecticides reduced populations of natural enemies by 10 to 20 percent in North American and European farming systems. Surprisingly, this effect was about the same as that associated with broadcast applications of pyrethroids.”

The team’s research appeared in the online journal PeerJ.

The team used a statistical method, called meta-analysis, to combine the results of more than 1,000 observations from 20 field studies across North America and Europe that tested the effects of seed-applied neonicotinoids on predatory insects. “Unfortunately, the available literature is difficult to interpret,” said Tooker. “Some studies show little influence of neonicotinoids presented as seed treatments on arthropod predators that are common in crop fields, whereas others show a strong influence of these seed treatments. By using a meta-analysis approach, we were able to combine the results of many studies to quantitatively reveal the overall influence of neonicotinoids on predator populations.”

Not only did the researchers find that neonicotinoid seed coatings significantly reduced natural enemy populations, they also found that the insecticide acted more strongly on insect predators than on spiders. In other words, spiders appeared to be less susceptible to neonicotinoids than insects, which is consistent with previous research.

“This result suggests that neonicotinoids are reducing populations of natural enemies at least partly through their toxic effects rather than simply by reducing the availability of their crop pest foods,” said Douglas. “After all, insects are more susceptible to these toxins than spiders, whereas the two groups should be similarly affected by a lack of food.” The researchers note that their results may help farmers and pest management professionals better weigh the costs and benefits of neonicotinoid seed treatments versus alternatives.

“Several governments have restricted the use of neonicotinoids out of concern for their possible effects on pollinators,” said Douglas. “But this raises the questions, ‘What will farmers do without these products? If they switch to broadcast applications of pyrethroids, will those products be better or worse for predatory insects?’ While our results do not speak to the pollinator issue, they do suggest that predatory insects are affected similarly by seed-applied neonicotinoids and broadcast pyrethroids.”

The answer to the problem, noted Tooker, lies in the application of integrated pest management (IPM), a strategy that uses a combination of techniques — which may or may not include the targeted use of insecticides — to control pests, rather than universally deploying prophylactic tactics like insecticidal seed coatings.

“Substantial research exists supporting the value of IPM for pest control,” he said. “It is the best chance we have of conserving beneficial insect species while maintaining productivity in our agricultural systems.”

Source: Science Daily

Dengue cases in Mumbai highest in 6 years

MUMBAI: The number of dengue cases recorded in the city this year has been the highest in the last six years. However, the good news is that fatalities have declined significantly over the last three years.

According to figures recently released by the state, Mumbai has recorded 1,088 cases so far this year and four confirmed deaths. The last time dengue cases had crossed the 1,000mark was in 2012. Within the state too, the highest number of cases were reported from the city. Dengue infected 6,376 people and claimed 26 lives in Maharashtra between January 1 and November 21this year. Doctors say the increase in incidence is a reason for concern as it can lead to longer hospital stays, lost manhours and bigger hospital expenses. “Dengue causes mortality in merely 1%-3% of cases. It is the morbidity that needs to be looked into closely,” said infectious disease consultant Dr Om Srivastava. He said that patients this ye ar had complained of pro blems in resuming their routine lives long after they had recovered from the mosquitoborne illness.

A senior physician from KEM Hospital in Parel too added that patients came to the hospital three months after recovering from the disease with complaints of lethargy . “In a few cases, the symptoms had persisted from six weeks to three months,” the doctor said. Srivastava added that many patients fail to follow the post-recovery regimen like drinking water and taking adequate rest which prolong their suffering.

Source: Times Of India