Living With Mate Guarding

Cricket

In many cricket species the male transfers nutrients to the female during mating. Females who mate with multiple males can produce more eggs. However, a male will produce the most eggs if all his sperm fertilize the eggs of the female. Male crickets package their sperm in a structure called a spermatophore. Once it is attached to the female, the sperm must leave the spermatophore to fertilize the eggs. This process requires time. Females will remove and consume the nutrient-rich spermatophore. How can the male protect his sperm? Males engage in a behavior known as mate guarding.

After mating, males will remain in contact with the female for an extended period. Male house crickets, Acheta domesticus, will remain with the female for about 30 minutes, maintaining antennal content and blocking the female from prematurely removing the spermatophore. Males of the decorated cricket, Gryllodes sigillatus, transfer a gelatinous spermatophylax in addition to the spermatophore. The female first consumes or discards the spermatophylax before removing the spermatophore. Females will spend more time consuming more nutritious spermatophylaxes, giving the male sperm more time to leave the spermatophore.

Battling Invasives

We hear most often about the invasive species that overwhelm all our efforts to halt their spread and takeover. There are some instances of success. The Asian Longhorned Beetle, Anoplophora glabripennis, is a native of China that attacks hardwoods. The successful eradication from Manhattan Island, New York was announced in May 2013.

Asian Longhorned Beetle
Image: Donald Duerr, USDA Forest Service, Bugwood.org

The Asian Longhorned Beetle was first detected in North America in Brooklyn, NY in 1996. Later it was detected in Chicago, IL in 1998, several counties in New Jersey between 2002 and 2004 and in the area around Worcester, MA between 2008 and 2010. Compared to other invasive beetle pests, the Asian Longhorned Beetle is larger, does not spread rapidly and increases its population more slowly. Its biology is amenable to eradication efforts. Asian Longhorned Beetle has been eradicated from Chicago; New Jersey was declared beetle free in April 2013; As of May 2013, it has been eradicated from Manhattan Island in New York where it threatened trees in Central Park.

Eradication is expensive, labor intensive and time consuming. However, eradication, once achieved reduces the need for future inspections and control efforts. Eradication requires that all trees in the area be extensively surveyed for signs of the beetle. Surveys often require tree climbers to inspect the upper reaches of trees for signs of beetle damage. Insecticide treatments can prevent nearby trees from becoming infested, however, the insecticides are not as effective against large beetle larvae. Those beetles must be controlled by destruction of the tree that harbors them, sometimes to the consternation of homeowners. The beetles migrate a limited distance of less than one mile per year. This delimits the initial area for eradication.

Eradication is cost effective compared to the potential damage this beetle could cause. Even more cost effective are efforts to prevent the entry of invasive species into North America.

Living With Entomologist Communication

People ask entomologists many questions about pest insects and random insects they encounter. The Insect IQ (knowledge about insects) matters. The more someone knows about insects, the easier it is to give them an answer. People who know more about insects are likely to provide more detailed and pertinent information. People who know little about insects can pose impossible questions. We are asked, “I found a little brown moth. Can you tell me what it is?” The questioner probably has little idea that there are thousands of “little brown moths” that fit the description. Cell phone cameras improve communications. A picture may show details useful to identification that escape the observer.

The internet is great for communication. We can post pictures that convey far more information than a written or spoken description. Visual information allows many curious people to answer their questions in a more timely and efficient manner. New pests can create communications issues. For example, most of the Public is unfamiliar with Emerald Ash Borer, an invasive species. People are concerned (rightly so) about their ash trees and inspect them for culprits. Any shiny green insect, no matter how little it resembles emerald ash borer, can generate a report that may require investigation. Entomologists need to both inform the public and focus on solving real problems. University of Nebraska has published a guide called “Emerald Ash Borer Look-Alikes”. The guide will hopefully communicate to an anxious public that not all shiny green insects are Emerald Ash Borers. Entomologists, known for a warped sense of humor may find this amusing.

http://extension.entm.purdue.edu/eab/images/eab_lookalikes.jpg

BioControl Evolution

Salt cedar (Tamarisk) was introduced to North America as an ornamental. Unfortunately, Salt Cedar is an invasive species that causes a variety of ecological and economic problems. Salt Cedar grows along river and stream banks and displaces native species important for wildlife habitat. Salt Cedar reduces available water by high evaporation rates. In dry areas, it can be a forest fire hazard.

Once established, invasive plants are difficult to eradicate but they may be controlled by importation of natural enemies such as insects. Diorhabda carinulata, an Asian beetle that feeds only on species of Tamarisk was imported as a possible control agent. Early releases were disappointing. Beetle populations rarely increased to levels high enough to give the desired level of control. Why were the beetles not effective?

Salt Cedar Beetle
Photo: werc.usgs.gov

Bean, Dalin and Dudley have been studying the biology of Diorhabda carinulata. They found that the beetle uses photoperiod cues to time its diapause (the dormant overwintering period). Initially released beetles would enter diapause as early as August in some areas, even though environmental conditions would allow additional generations to successfully develop. In 2012, some areas experienced more desirable beetle populations. This is attributed in part to the warm conditions during 2012. However, Bean and colleagues* have found that the beetles have been adapting to their new home. In one field site, the beetles are active for 16 additional days. This may not seem like a long time, but beetle populations reach their peak in the last generation. An additional generation can mean much larger populations.

This rapid evolution is the result of natural selection. In their home range, beetles that failed to enter diapause on time had offspring that did not have enough time to fully develop before adverse winter conditions arrived. Thus, beetles that delay diapause produce offspring with lower rates of survival. In their new home, beetles that diapause at a later date produce many more offspring than beetles that diapause early. Over several generations, the time when most beetles diapause shifts to a later date.

Will this beetle be the answer to Salt Cedar control? Only time will tell. Understanding the biology of insects used for biocontrol informs future efforts to control many of our invasive species.

*Bean, Dalin and Dudley. July 2012. Evolution of critical day length for diapause induction enables range expansion of Diorhabda carinulata, a biological control agent against tamarisk. Volume 5, Issue 5, pages 511–523.
DOI: 10.1111/j.1752-4571.2012.00262.x

Living With Science Patrons

Prior to the era of the modern government research grant, art and scientific research were largely funded by subsidies from wealthy patrons. Many of the Great Scientists and Artists of the Renaissance were supported by Patrons. However, Patrons were few and many budding (but poor and hungry) scientists abandoned their interests for lack of support. As a result, many of the problems of science and industry went unsolved. For the past two centuries, the government of the United States has promoted scientific discovery and applied science through the establishment of institutions such as Land Grant Colleges and Agricultural Experiment Stations. In recent years, governments have been sidetracked by focus on deficits and have allowed funding for scientific discoveries to decline.

In an age of declining support from government, where can scientists turn? Patrons still exist and can be cultivated. Researchers and their institution are turning more of their creative talents to fund raising. Businesses have made money from “Star Registry” that sells certificates to people who wish to name a star, often for a loved one. Why not allow people to pay to have an insect named after them? This is the approach being tried by the Bohart Museum. Through their “Biolegacy” program, Patrons can donate a minimum of $2500. The donation supports the work of the Museum with the potential to have a species named for the Patron. Groups might gather donations to honor a friend or mentor such as a retired science teacher. Could there be money in the darker side? Would an jilted lover get pay to name a cockroach after the Ex to exact revenge? Would political groups pay to have a pest insect named for an opposition politician?

The potential to raise money is enticing. What could be lost? Naming species based on obvious characters can be helpful to students learning a group for the first time. Fewer species might be named in honor of entomologists who devoted their careers to the taxonomy of a group. Will public support for science erode if the public perceives that science is a playground for the wealthy? In the short run, scientists need to replace funds lost to sequesters and cuts. The longer run funding questions will remain.

Part of the Purdue Entomology Research Collection

Living With Insect Media

Jussi Parikka has written a thought provoking and compelling book, Insect Media that explores the relationships between insects and technology. The idea of using nature as a model for human machines has a long standing history. As technology has advanced our ability to miniaturize our human creations, the usefulness of insect models has expanded.

Honey Bee

Insect Media explores in depth the use of insect metaphors during the emergence of Modern Biology in the 1800s. In the mid to late 1800s, the Darwinian concept of evolution replaced the idea of insects as the handiwork of a creator. Modern biology views living organisms as the result of adaptation to environment. Although the concept of living organisms changed during the 1800s, many of the ideas surrounding insects as models for technology and society survived the Darwinian revolution. Many amateurs took up the study of insects in the 1800s. Books about insects were popular best sellers of the time. As a result of popular entomology, sufficient numbers of people possessed a knowledge and interest in insects that allowed insect metaphors to be a used as a means to conceptualize and discuss emerging technologies.

Insect Media explores the idea of non-human means of communication. It is clear that insects can communicate using techniques, channels that are not available to humans. However, these communication techniques and channels can be and have been used by the computers and other machines that humans create. We often communicate about our machines using insect metaphors. Insect Media provides a context that explains why insects are so entwined with communication about our technology.

Friday Cat-erpillar Blogging: Living With Medication

Humans are successful as a species, in part because we find ways to treat and rid ourselves of parasites. Traditionally, many of our medicines come from plants. Can insects use plant “medicines” to treat their parasites?

Banded Wooly Bear Caterpillar

One of the wooly bear caterpillars, Grammia incorrupta, can be parasitized by the Tachinid fly, Exorista mella. Grammia incorrupta feeds on a variety of plants some of which contain potent toxins. Singer, Mace and Bernays* studied the effect of caterpillar diet on survival. They found that only 80 percent of the caterpillars survived on diet containing toxic pyrrolizidine alkaloids compared to 100 % on an optimal diet. However, if the caterpillars were parasitized by flies, over half the caterpillars feeding on pyrrolizidine alkaloids survived, while fewer than half the parasitized caterpillars survived on the optimal diet. When given a choice of diet, parasitized caterpillars consumed more pyrrolizidine alkaloids than unparasitized caterpillars. The study suggests that some caterpillars may respond to parasites by self-medication to improve their chance of survival.

*Singer MS, Mace KC, Bernays EA (2009) Self-Medication as Adaptive Plasticity: Increased Ingestion of Plant Toxins by Parasitized Caterpillars. PLoS ONE 4(3): e4796.
doi:10.1371/journal.pone.0004796