Study Questions        Exam 1

For each of the situations described in the questions below, address each statement.  Indicate if each statement is True or False and then justify your thinking.  If you think a statement is true, explain why.  If you think a statement is false, state why and then explain what would be necessary to make it true.  Be sure to address each point raised in each statement.  It is possible for all statements to be true or false.

1.  On afternoon while working in your flower garden, you observe butterflies and bees foraging.  As you work, you find that several of your plants are being eaten by caterpillars.  You notice that some of these caterpillars have already spun cocoons.  As you watch these different insects, you are correctly thinking that:

a.  Flight in both the butterflies and bees involves the flight muscles of the thorax and petiole pulling against the sternacosta, which arises from the scutoscutellar suture of the alinotum.

b.  Both the adult butterflies and bees have haustellate mouthparts, but the butterflies have sponging mouthparts in which the lacinia of the maxillae have been modified into a labellum, while the bees have siphoning mouthparts in which the glossa of the labium has become modified into piercing stylets.

c.  For the caterpillars that are feeding on the plants, JH titers remain above the threshold level during molting, while for those in cocoons the JH titers will drop below the critical level.

d.  The foraging honeybees are learning the location and time of day in which the flowers are producing nectar and pollen using the corpora allata of the tritocerebrum, while in the butterflies the innervation of the mouthparts is regulated by the corpora pedunculata of the thoracic ganglia.

e.  During molting in the caterpillars, bursicon released from the central body of the protocerebrum activates gene programs in epidermal cells and cause a new endocuticle to be produced, in which dark bands are laid down during the nighttime hours and light bands are produced during daylight hours and are heavily sclerotized.

2.  If an insect is an endopterygote, then:

a.  metamorphosis is gradual and wings develop as external buds.

b.  ecdysone levels rise steadily during each successive larval stage and gradually promote the development of adult characteristics.

c.  the wings cannot be flexed and folded flat over the back.

d.  the forewings would consist of an upper leathery (thickened) portion and a lower membranous portion.

3.  When you see a cockroach running across your kitchen countertop, you can correctly conclude that:

a.  the leg muscles move the legs by pushing and pulling against the tentorium and valvifers of the sternal sclerites of the thorax.

b.  the nervous impulses that regulate running involve the opening of K+ channels, which results in the massive outflow of Ca++.

c.  the skeleton associated with the joints of the legs is flexible because it is composed primarily of exocuticle in which resilin proteins have become bound to one another through the process of sclerotization.

d.  the legs articulate with the coxal cavity using the basalar and subalar.

ANSWERS

1. 

a.  False:  flight involves thoracic flight muscles pulling against phragma of the postnotum of the pro-, meso-, and metathoracic segments.  Petiole is modified first abdominal segment of hymenoptera and is not involved in flight.  Sternacosta not involve in flight, but provides attachment points for leg muscles, and it arises from sternacostal suture of the sternum,  not scutoscutellar suture (which provides rigidity to alinotum and divides alinotum into the scutum and scutellum).

b.  False:  both have haustellate mouthparts.  But, lepidopterans have siphoning mouthparts composed of modified galea of the maxilla.  Bees have chewing-lapping mouthparts, in which the mandibles are present and functional, and a "tongue" have evolved from the modified glossa of the labium.  Sponging moutpart are found in the non-biting diptera, and consist of the labellum (modified labium, not modified lacinia of maxilla, which make up the piercing-sucking mouthparts of Siphonapterans). 

c.  True:  In caterpillar (larval) stage, JH is above the threshold level so that at each molt it promotes larval characteristics.  In the pupal stage in the cocoon, JH drops below the critical level and this allows ecdysone to promote the development of adult characteristics during molting.

d.  False:  learning in bees is regualted by the corpora pedunculata (center for higher order behaviors) in the protocerebrum.  Corpora allata is involved in hormone secretion (prothorasicotropic hormone and JH for molting), not learning, and corpora allata is part of the hypocerebral ganglion, not located in the tritocerebrum.  Innervation of mouthparts comes from tritocerebrum, frontal ganglion and hypocerebral ganglion, not mushroom bodies (which are not located in the thoracic ganglia).

e.  False:  bursicon is released by brain centers (although not central body, which allows the two sides of the protocerebrum to communicate), but it causes the cuticle to sclerotize.  Ecdysone (produced by prothoracic gland in response to prothoracicotropic hormone released from corpora allata) is the hormone that causes epidermal cells to form the exuvial space, secrete molting fluid, and produce the new cuticle.  But the new endocutile is laid down in dark bands (produced during the day; all chitin fibers with same orientation) and light bands (produced at night; composed of lamella, each with a different orientation of chitin fibers) and endocuticle is not heavily sclerotized (exocuticle is).

2. 

a.  False:  endopterygotes have holometabolous (complete) metamorphosis in which there is a sudden and radical reorganization of the body into the adult form and the wings develop internally.  Graduate metamorphis and wing development from external buds is characteristic of exopterygotes.

b.  False:  adult characteristics arise from a steady decrease in the hemolymph titers of JH, which around the pupal molt, drop below a critical level and allow ecdysone to promote adult characteristics.

c.  False:  endopterygotes (and neopterus exopterygoes) have a wing hinge that allows wings to be flexed and folded flat against the body when at rest.  Paleopterous exopterygotes cannot do this.

d.  False:  this is characteritic of the wings of Order Hemiptera, which are neopterous exopterygotes, not endopterygotes.

3. 

a.  False:  leg muscles attach to and pull against the sternacosta (with sternal apophyses) and the plural ridge (with plural apophyses) in the thorax.  The tentorium is located in the head and provides attachment points for muscles of the mouth parts; valvifers are appendages of the last abdominal segment and make up the external genitalia.

b.  False:  (see you notes on the generation of an action potential)

c.  False:  joints are covered primarily by endocuticle which is flexible and has little sclerotization.  Sclerotization involves scerlotin proteins becoming linked together.  Resilin is a rubber like protein that makes up a scaffold around which the skeleton is built.

d.  False:  legs articulate with coxal cavity using the coxal articulation point and trochantin.  Basalar and subalar are two small sclerites of the pluron associated with the wing hinge.