Ypsolopha dentella (Y.dentella)is a moth that lives in the northeastern United States.It appears as a larva (the immature form that differs entirely from the adult moth)early in the spring, feeding on the young leaves of honeysuckle plants.Y.dentella larvae are well camouflaged.Predominantly green,they match the color of the leaves they eat.As additional defenses,the larvae also have the ability to squirm and to jump off a leaf and hang in the air using a silken thread.Squirming,or wiggling,is an escape mechanism they share with many small caterpillars,but Y.dentella manifests this behavior in the extreme.Release a Y.dentella larva on a smooth surface and poke it gently with a toothpick,and it will propel itself over the surface by twisting and turning with such speed that it will literally vanish from view.The response may last only seconds,but that is long enough to allow the larva to distance itself from the scene.
When a larva has wiggled its way to the edge of a leaf and can go no farther,it jumps,plunging into space,suspended by a slender silken thread that it squeezes from a small spigot that projects from just beneath the mouth.The spigot bears the openings of two large sac-like glands that take up a considerable portion of the larva’s body cavity and are bulging with the viscous liquid from which the silk is made.Jumping does not require that the larva take time to anchor the silken thread to the edge of the leaf before jumping.The silken thread is fastened to the larva’s cocoon,and the larva needs only to let out a piece of silk long enough to cover the distance to the leaf edge.It is therefore connected to home base at all times and free to squirm away and take a plunge at a moment’s notice.
When they plunge,the larvae drop some 10 to 20 centimeters or more,a considerable distance relative to a body length of 15 millimeters or less.In essence their plunging is another vanishing act,a trick that in combination with squirming enables the larvae to avoid trouble by leaving the scene.When the larvae plunge they drop virtually instantaneously.The rate at which they are able to convert liquid glandular precursor into silken strand is therefore quite remarkable.
The suspended larva,as a rule,does not remain hanging from its thread for long.Within minutes,it begins the slow process of climbing up the thread to return to its cocoon.To ascend,the larva pulls itself up along the cord,a short distance at a time,using its mouthparts to exert the pull and to tuck away the loops of slack reeled in as it proceeds upward.The process is elegant.The entire thread is stuffed into a holding space between the third pair of legs. When the larva completes its climb,it relinquishes the package, leaving it stuck to the leaf margin the moment it is back at home base.In so doing,the larva is essentially squandering a resource. Other silk producers are more conservation oriented.Spiders,for instance,when they take down their webs,eat the silk.
Jumping is doubtless effective against many predators,including ants and jumping spiders,but it comes at a price.Aside from the cost of the silk itself,which the larva needs to conserve for eventual cocoon production,jumping takes time.Although the larvae usually ascend within minutes,they sometimes remain suspended for over an hour.Potentially this wait could cut significantly into feeding time and therefore have a retarding effect on development.Whether it does depends on how often the larvae are attacked under normal circumstances,which has not been determined.But there is no question that predation pressure could be high at times upon Y. dentella larvae,particularly from ants.
One intriguing possibility is that jumping protects Y.dentella larvae against predation by wasps.No data on Y.dentella itself are available,but other caterpillars have been shown to avoid wasp attacks by resorting to squirming behavior.
题目：
1
Ypsolopha dentella (Y.dentella)is a moth that lives in the northeastern United States.It appears as a larva (the immature form that differs entirely from the adult moth)early in the spring, feeding on the young leaves of honeysuckle plants.Y.dentella larvae are well camouflaged.Predominantly green,they match the color of the leaves they eat.As additional defenses,the larvae also have the ability to squirm and to jump off a leaf and hang in the air using a silken thread.Squirming,or wiggling,is an escape mechanism they share with many small caterpillars,but Y.dentella manifests this behavior in the extreme.Release a Y.dentella larva on a smooth surface and poke it gently with a toothpick,and it will propel itself over the surface by twisting and turning with such speed that it will literally vanish from view.The response may last only seconds,but that is long enough to allow the larva to distance itself from the scene.
All of the following are mentioned in paragraph 1 as ways that Y.dentella larvae defend themselves against predators EXCEPT
Ahanging in the air on a thread
Bblending into their environment
Cpropelling themselves off a leaf
Dchanging colors quickly to match a surface
2
Ypsolopha dentella (Y.dentella)is a moth that lives in the northeastern United States.It appears as a larva (the immature form that differs entirely from the adult moth)early in the spring, feeding on the young leaves of honeysuckle plants.Y.dentella larvae are well camouflaged.Predominantly green,they match the color of the leaves they eat.As additional defenses,the larvae also have the ability to squirm and to jump off a leaf and hang in the air using a silken thread.Squirming,or wiggling,is an escape mechanism they share with many small caterpillars,but Y.dentella manifests this behavior in the extreme.Release a Y.dentella larva on a smooth surface and poke it gently with a toothpick,and it will propel itself over the surface by twisting and turning with such speed that it will literally vanish from view.The response may last only seconds,but that is long enough to allow the larva to distance itself from the scene.
Paragraph 1 suggests that,compared to other small caterpillar larvae,Y.dentella larvae
Ahave completely different escape mechanisms
Bhave responses to being poked that do not last as long
Care more difficult for researchers to locate
Dare able to escape from predators more quickly
3
When a larva has wiggled its way to the edge of a leaf and can go no farther,it jumps,plunging into space,suspended by a slender silken thread that it squeezes from a small spigot that projects from just beneath the mouth.The spigot bears the openings of two large sac-like glands that take up a considerable portion of the larva’s body cavity and are bulging with the viscous liquid from which the silk is made.Jumping does not require that the larva take time to anchor the silken thread to the edge of the leaf before jumping.The silken thread is fastened to the larva’s cocoon,and the larva needs only to let out a piece of silk long enough to cover the distance to the leaf edge.It is therefore connected to home base at all times and free to squirm away and take a plunge at a moment’s notice.
According to paragraph 2,why is the Y.dentella larva able to jump from a leaf at a moment’s notice?
AIt weighs very little because its body is full of silk.
BIt builds its cocoon on the very edge of the leaf.
CIt always remains attached to its cocoon by a silken thread.
DIts silken thread is strongly anchored to the edge of the leaf.
4
When they plunge,the larvae drop some 10 to 20 centimeters or more,a considerable distance relative to a body length of 15 millimeters or less.In essence their plunging is another vanishing act,a trick that in combination with squirming enables the larvae to avoid trouble by leaving the scene.When the larvae plunge they drop virtually instantaneously.The rate at which they are able to convert liquid glandular precursor into silken strand is therefore quite remarkable.
According to paragraph 3,Y.dentella larva does all of the following as part of plunging EXCEPT
Adropping a great distance in relationship to its size
Bsquirming great distances along the ground after plunging
Cproducing silk from a glandular liquid
Ddropping so quickly from a leaf that it seems to disappear
5
The suspended larva,as a rule,does not remain hanging from its thread for long.Within minutes,it begins the slow process of climbing up the thread to return to its cocoon.To ascend,the larva pulls itself up along the cord,a short distance at a time,using its mouthparts to exert the pull and to tuck away the loops of slack reeled in as it proceeds upward.The process is elegant.The entire thread is stuffed into a holding space between the third pair of legs. When the larva completes its climb,it relinquishes the package, leaving it stuck to the leaf margin the moment it is back at home base.In so doing,the larva is essentially squandering a resource. Other silk producers are more conservation oriented.Spiders,for instance,when they take down their webs,eat the silk.
Why does the author state that“Spiders,for instance,when they take down their webs,eat the silk”?
ATo acknowledge that some organisms do not use their silk for escaping predators
BTo illustrate that Y.dentella uses its silk differently from other species which try to conserve silk
CTo support the argument that other organisms may benefit from the silk produced by Y.dentella
DTo explain why some organisms are able to produce larger quantities of silk than others
6
The suspended larva,as a rule,does not remain hanging from its thread for long.Within minutes,it begins the slow process of climbing up the thread to return to its cocoon.To ascend,the larva pulls itself up along the cord,a short distance at a time,using its mouthparts to exert the pull and to tuck away the loops of slack reeled in as it proceeds upward.The process is elegant.The entire thread is stuffed into a holding space between the third pair of legs. When the larva completes its climb,it relinquishes the package, leaving it stuck to the leaf margin the moment it is back at home base.In so doing,the larva is essentially squandering a resource. Other silk producers are more conservation oriented.Spiders,for instance,when they take down their webs,eat the silk.
According to paragraph 4,what happens to the silken thread after the Y.dentella larva has climbed back up to the leaf?
AThe larva uses the silk for reconnecting to its cocoon.
BThe larva saves the silk for use during the next jump.
CThe larva eats the silk.
DThe larva deposits the silk at the edge of the leaf where it remains.
7
Jumping is doubtless effective against many predators,including ants and jumping spiders,but it comes at a price.Aside from the cost of the silk itself,which the larva needs to conserve for eventual cocoon production,jumping takes time.Although the larvae usually ascend within minutes,they sometimes remain suspended for over an hour.Potentially this wait could cut significantly into feeding time and therefore have a retarding effect on development.Whether it does depends on how often the larvae are attacked under normal circumstances,which has not been determined.But there is no question that predation pressure could be high at times upon Y. dentella larvae,particularly from ants.
The word“eventual'”in the passage is closest in meaning to
Afuture
Bnecessary
Csuccessful
Defficient
8
Jumping is doubtless effective against many predators,including ants and jumping spiders,but it comes at a price.Aside from the cost of the silk itself,which the larva needs to conserve for eventual cocoon production,jumping takes time.Although the larvae usually ascend within minutes,they sometimes remain suspended for over an hour.Potentially this wait could cut significantly into feeding time and therefore have a retarding effect on development.Whether it does depends on how often the larvae are attacked under normal circumstances,which has not been determined.But there is no question that predation pressure could be high at times upon Y. dentella larvae,particularly from ants.
Paragraph 5 suggests that larvae that are frequently attacked
Amight suffer from slowed growth and development
Bgradually lose the ability to produce silk
Cbecome more skilled at jumping and ascending
Dmove their cocoons in order to reduce the risk of predation
