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What kind of caterpillar type bug is this?

What kind of caterpillar type bug is this?


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I've made a photo using the reversed 58 mm lens and my cropped DSLR:

Could you please help? I really don't know where this came from.

I found it in Russia.


Likely to be a black carpet beetle larvae

http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7436.html

For more facts try: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7436.html Don't worry though, they live everywhere!

Wikipedia has some info on the family of beetles that they belong to (http://en.wikipedia.org/wiki/Dermestidae). I don't think they really cause any harm, except in natural history museums where they tend to munch the collections of animals… although this can also be a good thing:

'They are used in taxidermy and by natural history museums to clean animal skeletons' 1

1 VanClay, Mary. "Bitten By the Bug". www.johnsonstring.com. Retrieved November 10, 2012.


Caterpillar

Caterpillars ( / ˈ k æ t ər p ɪ l ər / CAT -ər-pil-ər) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths).

As with most common names, the application of the word is arbitrary, since the larvae of sawflies are commonly called caterpillars as well. [1] [2] Both lepidopteran and symphytan larvae have eruciform body shapes.

Caterpillars of most species are herbivorous (folivorous), but not all some (about 1%) are insectivorous, even cannibalistic. Some feed on other animal products for example, clothes moths feed on wool, and horn moths feed on the hooves and horns of dead ungulates.

Caterpillars are typically voracious feeders and many of them are among the most serious of agricultural pests. In fact many moth species are best known in their caterpillar stages because of the damage they cause to fruits and other agricultural produce, whereas the moths are obscure and do no direct harm. Conversely, various species of caterpillar are valued as sources of silk, as human or animal food, or for biological control of pest plants.


Control

The single attack of a leaf-feeding insect will seldom kill a healthy tree or shrub. Repeated defoliations, however, may weaken and make them susceptible to destruction by other insects, diseases, severe cold weather, drought, etc. Most of those listed above are not a serious threat.

Try to identify the specific insect before taking control measures. Your local Cooperative Extension center can help. Further information about some of the more serious caterpillar pests is contained in other specific insect pest notes.

Some pesticides are labeled for "caterpillars." Other pesticides may be labeled for certain types of caterpillars such as armyworms, bagworms, cankerworms, webworms. Some pesticides are even labeled for specific caterpillars such as yellownecked caterpillars or eastern tent caterpillars. A complete list of all such pesticides and all of their target pests is too long for this insect note. The Southeastern US Pest Control Guide for Nursery Crops and Landscape Plantings has a more complete list of pesticides and target pests. Bacterial insecticides such as Bacillus thuringiensis (B.t.) are useful only when caterpillars are small.


Caterpillars on cole crops in home gardens

Adult butterflies are commonly seen flying around plants during the day.

  • Adults are white butterflies with black spots on the forewings.
  • Eggs are yellow and oblong, and are on both upper and lower sides of leaves.
  • Caterpillars can grow up to 1 inch in length and are velvety green with faint yellow stripes running lengthwise down the back and sides.
  • They move sluggishly when prodded.

Cabbage looper (Trichoplusia ni):

Adults are nocturnal moths with a 1½-inch wing span.

  • Adult moths have mottled grayish brown wings.
  • A small silvery white figure 8 is in the middle of each of the front wings.
  • Eggs are creamy white, aspirin-shaped, and about the size of a pin head.
  • Adults lay eggs on the undersides of the lower leaves.
  • Caterpillars are pale green with narrow white lines running down each side.
  • Full grown caterpillars are about 1½ inches long.

Cabbage looper caterpillars have no legs in their middle sections and make a characteristic looping motion as they move across vegetation.

Diamondback moths (Plutella xylostella):

Adult moths are nocturnal flyers.

  • Moths are light brown and slender.
  • The folded wings show a pattern of three white diamonds.
  • Eggs are laid near leaf veins on the leaf, and are creamy white and tiny.
  • Caterpillars are light green, tapered at both ends and grow up to 1/3 inch long, much smaller than imported cabbageworms and cabbage loopers.
  • They wiggle vigorously when touched.

All three species have similar life cycles.

  • Eggs hatch into caterpillars and then damage plants.
  • After feeding for weeks on cole crops, the larvae change into pupae in protected areas on the plants.
  • Then they emerge as adults.

Imported cabbageworms

In the upper Midwest, they live through the winter in green pupal cases.

  • Adults begin to appear in gardens in mid-May.
  • They are a problem through the rest of the growing season.
  • 3 to 5 overlapping generations a year.

Cabbage loopers

They do not survive the winter in the upper Midwest.

  • Moths migrate from the south into Minnesota from early July to late August.
  • 1 to 3 generations a year during the growing season depending on their arrival time and late summer temperatures.

Diamondback moths

In the upper Midwest, they live through the winter as adults in protected locations.

  • Moths begin to appear in mid-May.
  • Can be pests through the remainder of the growing season.
  • Generally 3 to 5 generations a year.

Damage caused by caterpillars

The caterpillars of all three species feed between the large veins and midribs of cole crops.

Imported cabbageworm and cabbage looper feeding

  • Young caterpillars produce small holes in leaves that do not break through to the upper leaf surface
  • Larger caterpillars chew large, ragged holes in the leaves leaving the large veins intact

In cabbage, broccoli or cauliflower, larger caterpillars crawl toward the center and leave large amounts of frass (fecal matter).

Diamondback larva feeding

  • Starts feeding inside the leaves, then moves to the outside of the leaves.
  • Eats all the leaf tissue except the upper layer, giving a windowpane look.

Cole crops can tolerate some feeding damage.

  • Young seedlings and transplants are most susceptible to injury.
  • Severe defoliation of young seedlings and transplants can cause distorted growth or even death.
  • Extensive feeding can also prevent the head formation of cabbage, cauliflower and broccoli.
  • Older plants can tolerate some defoliation, with little effect on yield. Do not allow defoliation to exceed 30 percent of leaves.

How to protect your garden from caterpillars

Check for caterpillars and their feeding damage on both sides of leaves on cole crops. Check at least once a week right after planting and more often as the season progresses.

Make gardens less welcoming to pests

  • Destroy crop residue immediately to eliminate protected sites that imported cabbageworms may use to survive the winter.
  • Remove weeds from the Brassicaceae family like wild mustard, peppergrass and shepherd's purse, as they are alternate hosts for these pests.

Handpick and drop the caterpillars into a pail of soapy water to kill them.

Floating row covers made up of lightweight all-purpose garden fabric keep the adult moths from laying eggs on plants.

  • Fit the row covers directly over garden plants or over metal hoops/wooden frame to cover the cole crops at seeding or transplanting.
  • Remove row covers after harvesting the crop.

Natural enemies can reduce caterpillar numbers

Predators such as, paper wasps, and parasitic flies and wasps, such as the parasitic wasp, Cotesia glomerata, are natural enemies of cabbage looper, imported cabbageworm and diamondback moth.

  • These small wasps and flies do not sting or bite people and occur naturally in gardens.
  • They develop within the caterpillar, pupae or eggs, and eventually kill their hosts.

The best time to treat caterpillars is while they are still small and before they cause too much feeding damage. Pesticides are less effective in killing larger caterpillars.

There are several low risk pesticide options that have less impact on natural enemies and pollinators such as bees and flies.

  • Pyrethrins need to be sprayed directly on the caterpillars to be effective
  • Neem is a plant-based pesticide that does not kill insects, but it causes them to stop feeding and they eventually die.
  • Spinosad is derived from a naturally occurring soil-dwelling microorganism, that is effective against chewing insects like caterpillars.
  • Bacillius thuringiensis (Bt) is a bacterium that occurs naturally in the soil. Caterpillars must eat it to be effective. Get good coverage on the leaves when spraying.

Conventional, or broad-spectrum pesticides, are longer lasting but they can kill natural enemies. Common examples of broad spectrum pesticides include permethrin, beta-cyfluthrin, and lambda-cyhalothrin.

Jeffrey Hahn, Extension entomologist and Suzanne Wold-Burkness, College of Food, Agricultural and Natural Resource Sciences


Discussion

In this study, we investigated the phenomenon of clicking caterpillars in the superfamily Bombycoidea and focused primarily on one silkmoth species, A. polyphemus. Upon disturbance, A. polyphemus produce airborne sounds that often precede or accompany defensive regurgitation. Our hypothesis that sound production warns predators of an impending regurgitant defense was supported by several lines of experimental evidence. In the following discussion we examine our results with respect to the testable predictions outlined in the introduction, propose alternative hypotheses for the function of signaling in A. polyphemus larvae, and discuss the concept of sound production in caterpillars by examining the advantages of acoustic, rather than visual, aposematic signals.

Fifth instar (A) Actias luna and (B) Manduca sextalarvae. Scale bars, 1 cm. (C,D) Oscillograms of sounds produced by A. luna and M. sexta, respectively, showing the typical click patterns of larvae after being pinched with forceps. (E,F) Clicks from the trains in C and D, respectively, with an expanded time scale showing that clicks generally have two components.

Fifth instar (A) Actias luna and (B) Manduca sextalarvae. Scale bars, 1 cm. (C,D) Oscillograms of sounds produced by A. luna and M. sexta, respectively, showing the typical click patterns of larvae after being pinched with forceps. (E,F) Clicks from the trains in C and D, respectively, with an expanded time scale showing that clicks generally have two components.

Aposematism

The term aposematism was coined by Edward Poulton in 1890. In its original context, he defined `aposematic colouration' as “an appearance which warns off enemies because it denotes something unpleasant or dangerous or which directs the attention of an enemy to some specially defended, or merely non-vital part or which warns off other individuals of the same species” (Poulton,1890). In recent years, it has been shown that aposematism evolved because predators learn to avoid brightly patterned or otherwise conspicuous prey more rapidly than cryptic prey(Gittleman and Harvey, 1980 Gittleman et al., 1980 Sherratt, 2002). Many experimental studies on aposematism have focused primarily on systems involving brightly patterned visual displays (for reviews, see Cott, 1940 Wickler, 1968 Guilford, 1990). However, the displays of aposematic animals do not always rely on colouration. In fact, the term aposematism has often been used to describe warning odours (e.g. Nishida et al., 1996 Schmidt, 2004) and sounds(e.g. Dunning and Krüger,1995 Kirchner and Röschard, 1999 Hristov and Conner, 2005). Therefore, we will use the term acoustic aposematism synonymously with warning sounds.

Are clicks emitted by A. polyphemus acoustic aposematic signals?

Our experimental results support several predictions designed to test the acoustic aposematism hypothesis. The first prediction, that sound production is associated with a predator attack, was supported. Many forms of disturbance, including blowing on the larvae or jarring their enclosures,caused the larvae to produce sound. In addition, simulated predator attacks with forceps and attacks by chicks strongly associated sound production with physical disturbance. The second prediction, that escalation in attack rate is positively correlated with the amount of signaling, was also supported. An increase in the number of pinches administered to the larvae was significantly associated with an increase in the number of acoustic signals produced. On average, larvae that were administered five consecutive pinches produced more than twice as many clicks over a 60 s period than did larvae that were pinched only once or twice.

Our third prediction states that natural predators should be capable of hearing the acoustic signal. The clicks produced by A. polyphemuslarvae are broadband in structure, with an upper frequency limit that extends into ultrasound. A broad bandwidth is a distinguishing feature of insect disturbance sounds (Masters,1979). Warning sounds typically display average bandwidths of approximately 40 kHz at 10 dB below peak frequency(Masters, 1980). Several clicks analyzed in this study had bandwidths at –12 and –18 dB that spanned greater than 40 kHz. The broad nature of A. polyphemusclicks permit them to be perceived by a diversity of predators whose optimal hearing ranges may not coincide. Larval Lepidoptera are common prey items of gleaning bats (e.g. Kalka and Kalko,2006 Wilson and Barclay,2006). Thus, the high frequency component of clicks (20 kHz and above) may be perceived by bats whose best hearing range extends into the ultrasound spectrum (e.g. Neuweiler,1989). Likewise, the lower frequency component of clicks (20 kHz and below) is within the optimal hearing range of avian predators (e.g. Schwartzkopff, 1955 Frings and Cook, 1964 Dooling, 1991). It is also possible that praying mantids can hear clicks. Mantid hearing, believed to function primarily in bat detection, is most acute at ultrasonic frequencies,generally between 25 and 50 kHz (Yager,1999). The sound intensity of clicks was determined to be 58.1–78.8 dB peSPL at 10 cm. Upon attack, most predators would be even closer to the larvae than 10 cm. It is therefore reasonable to assume that clicks are well within the hearing threshold of their natural predators.

The fourth prediction, which states that regurgitant is adverse to predators, was supported by results obtained from the invertebrate and vertebrate bioassays. Mice preferentially consumed control diet over diet containing regurgitant. Similarly, ants were quicker to accept control mealworms than those coated in regurgitant, and were more likely to preen following contact with regurgitant. These results demonstrate that the regurgitant does afford some degree of protection against natural enemies. In addition, the fact that two predators as distantly related as ants and mice were deterred to some degree suggests that the regurgitant is effective against a range of predators. Both mice and ants did accept a portion of food items containing regurgitant, suggesting that regurgitating larvae may still experience moderate levels of predation. Two possible reasons account for the adverse quality of the regurgitant, which are not mutually exclusive. The regurgitant itself may gum up the mouthparts of attacking predators (like ants), or it may contain chemical compounds that render it distasteful. The composition of A. polyphemus regurgitant is currently unknown. If the adverse nature of the regurgitant is related to chemistry, it remains to be seen whether the defensive compounds are synthesized de novo or acquired through host plant secondary chemistry.

To our knowledge, regurgitation had not been previously reported in A. polyphemus larvae. Defensive regurgitation is widespread in insects(Eisner, 1970 Blum, 1981), but is not necessarily a ubiquitous defense strategy of caterpillars(Grant, 2006). Despite this lack of ubiquity, several studies have demonstrated the effective use of regurgitation by certain species of larvae in interactions with natural enemies (e.g. Gentry and Dyer,2002 Peterson et al.,1987 Cornelius and Bernays,1995 Theodoratus and Bowers,1999). Because regurgitation can be an energetically costly defensive response (Bowers,2003), A. polyphemus larvae attempt to reduce the cost by re-imbibing their regurgitant and accurately directing their mouths towards their attacker.

The final prediction states that the acoustic signal will most often precede or accompany regurgitation. In attack experiments with forceps, larvae predominantly produced sound prior to regurgitation. When attacked by chicks,many larvae responded with simultaneous sound production and regurgitation. Although force was not quantitatively measured in attack experiments, it was evident that chicks attacked the larvae much more forcibly than the pinches administered by forceps. Presumably, a forceful attack might result in a more aggressive defensive response, thereby necessitating larvae to produce sound in conjunction with, rather than, preceding defensive regurgitation.

Alternative hypotheses

Our hypothesis has been strongly supported in this study. However, it is prudent to consider alternative hypotheses, since airborne sound production by caterpillars has never been experimentally examined before. What are other possible functions for clicking by A. polyphemus larvae? First, they may be producing sounds in social interactions with conspecifics. However, in this study, sound production was not observed during any interactions between caterpillars. In addition, A. polyphemus larvae are insensitive to airborne sounds and appear to lack hearing organs, which strongly suggests they would be unable to detect the clicks of nearby caterpillars. Furthermore, A. polyphemus larvae are not gregarious as late instars, casting further doubt that the intended receiver of the acoustic signals would be a conspecific.

Second, sound production may be an incidental sound caused by regurgitation. However, as was demonstrated in the attack experiments with forceps, larvae are capable of regurgitating without clicking, and clicking without regurgitating. Furthermore, results from the comparative study indicate that several species of Bombycoidea readily regurgitate without producing sound. Since the ability to produce sound is independent from the ability to regurgitate, this hypothesis has little merit. While it is evident that clicking is not a by-product of regurgitation, an interesting possibility remains that sound production may have evolved from movement of the mouthparts while regurgitating or biting in response to an attack.

A third alternative hypothesis is that the clicks function as startle sounds. In fact, the first three predictions discussed here also provide support for this hypothesis. However, an important prediction to support the startle hypothesis would be that larvae attempt to escape following sound production. We did not observe any form of dispersal behaviour following attacks with forceps or by chicks, casting doubt on the validity of the startle hypothesis. In numerous field studies with A. polyphemus,larvae tend to move very little, even when attacked by multiple parasitoids(G.H.B., unpublished observation).

Comparative study

Comparative evidence suggests that the phenomenon of clicking caterpillars is widespread. In addition to A. polyphemus larvae, mandibular clicking has been reported in a number of species from the families Saturniidae and Sphingidae, two of which were identified for the first time in this study. A. luna and M. sexta produced broadband clicks with their mandibles when disturbed, clicking typically preceded defensive regurgitation, and no form of escape behaviour followed sound production. These observations provide additional support that clicks function as acoustic aposematic signals. It is surprising that other studies have not previously reported on sound production in these two species, particularly for M. sexta. In 2001, a detailed account of the defensive responses of laboratory-reared and wild M. sexta larvae following a series of simulated attack experiments was published(Walters et al., 2001). Although thrashing, striking and defensive regurgitation were reported, no mention was made regarding sound production.

One interesting difference between A. polyphemus clicks and the clicks produced by A. luna and M. sexta larvae is the spectral qualities of the signals. A. luna and M. sextaproduce clicks with most energy at 21.5 kHz and 38.0 kHz, respectively. Both values are considerably higher than the peak frequency produced by A. polyphemus (13.8 kHz). The high frequency component of clicks produced by A. luna and M. sexta larvae may be an incidental result of structural differences in mouthparts, or may lend additional support to the idea that clicks are directed towards gleaning bats.

Several species of Bombycoidea that we tested did not produce sound(Table 2). In fact, in one instance, sound production was not present in a species previously reported as sound-producing. Mandibular clicking was described in Smerinthus geminatus (reclassified as S. jamaicensis), when disturbed(Sanborn, 1868). In our study,sound production could not be induced in any of the S. jamaicensislarvae. It is possible that sound production is a regional characteristic in certain populations. This might account for the exclusion of sound production as one of the defensive responses of M. sexta larvae(Walters et al., 2001). However, sound production is not a regional characteristic for A. polyphemus, since larvae from Ontario and Prince Edward Island, Canada,and Massachusetts, USA all produce sound. The incongruence of our results with the observations of Sanborn necessitates that more S. jamaicensislarvae be tested for sound production in the future.

Currently, airborne sound production has been reported (including our data)for at least nine species belonging to the superfamily Bombycoidea. However,sound production does not occur in all species. Although it may be too early to make generalizations about why some larvae produce sound while others do not, possible explanations include the size of larvae and their mouthparts,the degree of warning colouration (see below) and taxonomy. To date, sound production has only been reported in species from two of the nine Bombycoidea families, namely the Saturniidae and Sphingidae, possibly because larvae from the other families are too small to make audible sounds.

The evolution of acoustic, rather than, visual aposematic signals

Many animals employ the use of sounds in conjunction with aposematic colouration. It is thought that additional signal components act to reinforce the association between colouration and unpalatability, a strategy referred to as multicomponent or multimodal signaling(Partan and Marler, 1999 Rowe, 1999). The use of multiple signals increases the efficacy of information transfer by acting on several sense modalities in the predator (e.g. Rowe and Guilford, 1999). However, if pairing a visual cue with an acoustic one helps to reinforce the message of unprofitability to potential predators, it begs the question: why are A. polyphemus and other sound-producing larvae cryptically coloured? One reason might be that clicks produced by Bombycoidea larvae are primarily directed towards auditory predators, rather than visual ones. This is similar to the argument (Ratcliffe and Fullard, 2005) that the brightly coloured dogbane tiger moth, Cycnia tenera, produces ultrasonic clicks that serve as defensive signals against vision-poor insectivorous bats. However, it is possible that the use of acoustic signals without conspicuous colouration is advantageous because it does not compromise the caterpillars' ability to remain camouflaged. Acoustic warnings, unlike visual ones, are not `on' all the time. Rather, they are only employed once an attack by a predator has been initiated, presumably because the continuous production of sound, unlike the continuous display of colour, is energetically costly. Cryptic colouration permits vulnerable larvae to remain as inconspicuous as possible up until the moment of attack. This allows for protection against an entire range of predators that vary in their degree of visual acuity. However, for our reasoning to be upheld, it must be shown that A. polyphemus (and other sound-producing larvae) are, in fact, visually cryptic to their predators.

Conclusion

Upon discovering that A. polyphemus larvae produce sound, the aim of this study was to identify the mechanism of sound production, to characterize the acoustic signals and to test the hypothesis that A. polyphemus larvae and several other species of Bombycoidea are producing sounds that function as acoustic aposematic signals. Several lines of experimental evidence were provided to lend support to our hypothesis. In the future, it will be important to demonstrate the effectiveness of sound production and regurgitation at deterring natural predators from attacking larvae. An experiment that monitors the behaviours of experienced predators who have previously encountered the regurgitant will be significant in lending support to the acoustic aposematism hypothesis. Furthermore, chemical analysis of the regurgitant with bioassay-guided fractionation might help to resolve its deterrent qualities. Lastly, an investigation into additional sound-producing species will assist in providing insight into the evolution of this interesting phenomenon.


Tent Caterpillars

Several types of caterpillars create tentlike webs in tree and shrub branches in spring. Known collectively as tent caterpillars, they weave unsightly webs and devour plant leaves. The protective webs grow along with the hungry larvae. Depending on the species, these pests may favor small fruit trees such as cherries and crabapples, but they attack many other trees and ornamental shrubs. Defoliated plants are left weakened and susceptible to other insect pests and diseases.

Identification: Eastern tent caterpillars, often mistaken for gypsy moth larvae, grow up to 2 inches long. Fine, reddish hairs cover their black bodies. A white stripe runs down their backs, and pale blue spots line their sides. Other species look similar from afar, but vary in their markings. Adult tent caterpillars are reddish-brown moths with two white bars on their forewings. Their eggs overwinter in shiny, black egg masses that encircle twigs.

Signs/Damage: Large, silky white webs in the forks of tree and shrub branches in early spring indicate tent caterpillars are present. The pests come outside the tents to feed. Branches within several feet of their tents are stripped of leaves.

Control: Effective tent caterpillar control targets these pests in early spring when caterpillars and webs are small. For large trees more than 10 feet tall, consider contacting a professional. For smaller trees and shrubs, GardenTech ® brand offers highly effective products that kill tent caterpillars by contact and keep protecting for up to three months:

  • Sevin ® Insect Killer Concentrate is ideal for treating shrubs and small trees thoroughly to protect against emerging caterpillars and treat active infestations. Used with a pump-style sprayer, the product provides broad coverage and direct treatment of webs and their surrounding areas. Cover all plant surfaces thoroughly, paying special attention to forks where branches meet.
  • Sevin ® Insect Killer Ready to Spray simplifies treating tent caterpillars before and after their tents appear. The product attaches to a common garden hose to measure and mix automatically as you spray. Cover all plants surfaces thoroughly, and treat tents directly. Caterpillars contact the spray as they go in and out to feed.

Tip: Prune overwintering egg masses from trees and shrubs before they can hatch. Remove webs on cool or rainy days, when caterpillars usually hide inside.

Always read product labels and follow the instructions carefully, including pre-harvest intervals for fruits and other edible crops.

GardenTech is a registered trademark of Gulfstream Home and Garden, Inc.


Prevention: How to Get Rid of Caterpillar

It is important to remember that not all of these insects are harmful, but they may harm plants in farm fields or your garden. If you notice them in an area where you want to get rid of them, then there are at least four methods that you may want to try.

First, you can hand pick them off your plants. This method is most effective if you have a small area and catch caterpillars in the area when there are only a few. Sometimes, spraying the area with water is an effective way to encourage caterpillars to move on.

Secondly, if the insect has built nests, you can use a stick or other object to knock down the nest and tear it apart. You need to destroy the nests so that the eggs inside them do not turn into more caterpillars. Since caterpillars usually return to the nest at night, this method works best when done in the evening or early morning.

Third, you can use Bacillus thuringiensis to kill them. Bacillus thuringiensis is a soil bacterium that destroys the stomach of caterpillars.

Another option is to make a deterrent at home. Take a little molasses and mix it with water and dish soap. Spray it where you see these insects. They do not like the taste, and they will move on to another area.


It’s usually moth caterpillars that make cocoons. They make liquid silk in their salivary (spit) glands and then drool it through an opening in their lip called a spinneret. It hardens into a thread when it comes into contact with the air and the caterpillar wraps it round itself to make the cocoon.

Not exactly, but they do have two tooth-like mouth parts called mandibles that they use to bite and chew. They work from side-to-side, not up and down like our teeth.

This puss moth caterpillar is using its mandibles to feed on leaves.

Credit: Richard Becker / WTML


Wax Moth Caterpillars Found to Eat Polyethylene

An international team of researchers from Spain and the United Kingdom has found that a caterpillar of the greater wax moth (Galleria mellonella) — commonly known as a wax worm — has the ability to biodegrade polyethylene.

Polyethylene degradation by wax worms. Left: plastic bag after exposure to about 100 wax worms for 12 hours Right: magnification of the area indicated in the image at left. Image credit: Bombelli et al, doi: 10.1016/j.cub.2017.02.060.

Polyethylene is the most commonly used plastic in the world: about 80 million tons are made annually.

It is largely utilized in packaging: nearly 50% of polyethylene is used to produce plastic films for food storage as well as agricultural and environmental use the remainder is used to produce plastic bottles and injection-molded products.

Polyethylene is highly resistant to breaking down, and even when it does the smaller pieces choke up ecosystems without degrading.

The environmental toll is a heavy one. Yet nature may provide an answer.

“We have found that the larva of a common insect is able to biodegrade one of the toughest, most resilient, and most used plastics,” said Dr. Federica Bertocchini, a researcher at the Institute of Biomedicine and Biotechnology of Cantabria in Spain.

A chance discovery occurred when Dr. Bertocchini, who is also an amateur beekeeper, was removing the parasitic pests from the honeycombs in her hives.

The worms were temporarily kept in a typical plastic shopping bag that became riddled with holes.

Further study showed that the worms can do damage to a plastic bag in less than an hour. After 12 hours, there was a reduction in plastic mass of 92 mg from the bag.

“The degradation rate is extremely fast compared to other recent discoveries, such as bacteria reported last year to biodegrade some plastics at a rate of just 0.13 mg a day,” the researchers said.

Dr. Bertocchini and co-authors showed that the wax worms were not only ingesting the plastic, they were also chemically transforming the polyethylene into ethylene glycol.

Although wax worms wouldn’t normally eat plastic, the researchers suspect that their ability is a byproduct of their natural habits.

In the wild, wax worms live as parasites in bee colonies. Wax moths lay their eggs inside hives where the worms hatch and grow on beeswax — hence the name.

The molecular details of wax biodegradation require further investigation, but it’s likely that digesting beeswax and polyethylene involves breaking down similar types of chemical bonds.

“Wax is a polymer, a sort of ‘natural plastic,’ and has a chemical structure not dissimilar to polyethylene,” explained Dr. Bertocchini, who is the lead co-author of a paper published in the journal Current Biology.

“If a single enzyme is responsible for this chemical process, its reproduction on a large scale using biotechnological methods should be achievable,” added first author Dr. Paolo Bombelli, a postdoctoral researcher in the Department of Biochemistry at the University of Cambridge.

“We are planning to implement this finding into a viable way to get rid of plastic waste, working towards a solution to save our oceans, rivers, and all the environment from the unavoidable consequences of plastic accumulation,” Dr. Bertocchini said.

“However, we should not feel justified to dump polyethylene deliberately in our environment just because we now know how to biodegrade it.”


How Caterpillars Work

A caterpillar's life starts with a textured, patterned egg and ends with a chrysalis -- a protective covering in which the caterpillar pupates, or undergoes a metamorphosis. Once the insect leaves the chrysalis, it's a full-grown butterfly or moth. It's the same species as it was before, but it no longer looks much like a caterpillar.

Between egg and chrysalis are a series of molts, in which the caterpillar sheds its too-tight skin, typically eating it afterward. This gives the caterpillar a little extra nourishment and also gets rid of evidence that could attract predators. The stage between each molt is called an instar, and most caterpillars go through five of them, growing very quickly and consuming lots of food to power their metamorphosis. The length of each instar varies based on the caterpillar's species, its food intake and the weather. Molting gives caterpillars more room to move, but it doesn't wipe out what they've learned about their environment -- most likely, their memory lasts over one or two molts.

A caterpillar's body is basically a tube for processing and storing food. A set of mouth parts lets the caterpillar chew its food -- typically leaves and other plant parts. The mouth empties into a very long intestine with fore and hind parts. Here, the caterpillar's digestive system breaks down the food and eventually stores it in a layer of fat called the fat body.

Six legs attached to the thorax let the caterpillar move around. Additional pairs of prolegs support and move the length of the caterpillar's abdomen. These prolegs end in small, hook-like suction cups called crochets. Since prolegs don't have segments or joints, they're not real legs, so even though it doesn't look like it, a caterpillar is a six-legged animal.

Most caterpillars move in one of two ways. Some crawl, moving each pair of prolegs and their true legs in sequence. Others, like the caterpillars of geometer moths, have no prolegs in the middle part of their abdomen. These caterpillars move in little arches, appearing to measure the surface under them.

The rest of the caterpillar's body lets it survive and get around:

  • Spiracles are holes in the caterpillar's sides through which it breathes.
  • Antennae provide sensory input, particularly relating to taste and smell.
  • In many species, false eyes help distract predators while real eyes allow the caterpillar to see.
  • Hairs, spines and quills called setae can deter predators and even carry toxins and irritants.
  • An osmeterium, found on swallowtail caterpillars, produces a foul-smelling substance that deters predators.

Caterpillars also have spinnerets, or silk-producing organs, in their heads. Next, we'll look at how silk can save a caterpillar's life, why it effects how quickly a caterpillar grows and why it's crucial to a successful metamorphosis.

Almost all caterpillars are herbivores, but there are some exceptions. Some butterflies, like Australia's Liphyra brassolis, lay their eggs in anthills. These eggs are disguised with waxes and pheromones, or scent chemicals, so the nearby ants don't notice them. When they hatch, these caterpillars eat ants and ant brood, or larvae. A few caterpillar species eat even larger animals -- several Hawaiian species eat snails after tying them to twigs with silk.