insect muscles
100: What type of muscle tissue do insects possess (striated, smooth, or cardiac)?
100: Insects have striated (skeletal) muscle.
100: Give one example of an insect group with direct flight and one example with indirect flight.
100: Direct example: Odonata (dragonflies); Indirect example: Hymenoptera (bees) or Diptera (flies).
100: State the Paranotal Origin idea for wing origin in one sentence.
100: Paranotal Origin: wings evolved as outgrowths (paranotal lobes) of the thoracic terga (not appendicular) that were used for gliding.
100: Are insects endothermic or ectothermic, and what does that term mean for body temperature regulation?
100: Insects are ectothermic — their body temperature largely follows ambient temperature and they rely on external heat sources/behavior to regulate temperature.
100: What is voltinism?
100: Voltinism is the number of generations an organism (insect) produces per year.
200: What is an apodeme and what is its function in insects?
200: An apodeme is an internal cuticular ingrowth that serves as a muscle attachment site, transmitting muscle force to move body parts.
200: In the direct flight mechanism, where are the main flight muscles attached?
Direct flight muscles attach to the wing base (directly on sclerites at the wing hinge) and the other side attaches internally to the thorax.
200: State the Exite Origin idea for wing origin in one sentence.
200: Exite Origin: wings evolved from articulated limb exites (appendage-origin), homologous to gill or leg branches.
200: Name two behavioral ways ectothermic insects can elevate their body temperature.
200: Behavioral methods: basking in sun, shivering (pre-flight thermogenesis), orienting body to maximize solar absorption, seeking warmer microhabitats. (Any two.)
200: Define univoltine and multivoltine (one sentence each).
200: Univoltine: one generation per year. Multivoltine: multiple generations per year (two or more).
300: What are tonofibrillae and where are they found?
300: Tonofibrillae are fine fibrous connections between the muscle and apodeme (or cuticle) that transmit force at a microscopic level.
Do muscles push or pull?
muscles only pull.
300: Give one main criticism of the Paranotal Origin hypothesis.
300: Criticism: Paranotal structures lack articulation and musculature necessary to explain active flapping and cannot easily explain the observed vein and hinge homologies.
300: List three physiological or behavioral strategies used by freezing-susceptible insects to survive cold (give three distinct strategies).
300: Three strategies: supercooling (lowering body fluid freezing point via cryoprotectants), producing antifreeze compounds (polyols, sugars), behavioral roosting/aggregation to reduce heat loss; additionally, producing insulating hairs or selecting microhabitats.
300: Give one example of an insect with a very short lifespan (adult stage) and one example of an insect with a very long lifespan (whole life cycle), with species names if possible.
300: Short example: mayflies (adult life often hours to days) — Ephemeroptera species; Long example: periodical cicadas (Magicicada spp.) with 13- or 17-year life cycles (from egg to adult emergence).
400: Describe the mechanical difference between monocondylic and dicondylic joints (movement range vs. strength).
400: Monocondylic joints have a single articulation point allowing more rotational freedom but less locking/stability; dicondylic joints have two articulation points that constrain movement to a plane but provide greater strength and stability.
400: In the indirect flight mechanism, where do the main muscles attach (to which part of the thorax)
400: Indirect flight muscles attach to the thoracic cuticle (not directly to the wing base). The two main groups are the dorsoventral muscles (up and down) and the dorso-longitudinal muscles (forward and back).
400: Give one piece of evidence that supports the Exite Origin (appendicular/exite) hypothesis.
400: Support for Exite: developmental and genetic evidence showing shared gene expression between wings and limb/appendage structures (exites), and fossil/exoskeleton homologies.
400: Explain how Ice Nucleating Agents (INAs) function in freezing-tolerant insects to control freezing.
400: INAs (Ice Nucleating Agents) are substances (often microbial or host-produced proteins) that provide nucleation sites so ice formation begins at higher subzero temperatures in a controlled manner; freezing-tolerant insects use INAs to localize and control ice formation to extracellular spaces, protecting cells from intracellular ice damage.
400: Explain the difference between diapause and quiescence.
400: Diapause is a hormonally programmed, developmentally arrested state with metabolic suppression and anticipatory timing (often seasonal) whereas quiescence is an immediate, reversible halt in development triggered directly by unfavorable conditions (no long-term hormonal program).
500: Name two structures (internal or connective) that transmit muscle force to the exoskeleton and briefly describe how each does so.
500: Apodemes and tendinous-like cuticular fibers (e.g., tonofibrillae); apodemes act as internal levers/anchor points, tonofibrillae transmit force from muscle fibers to apodeme/cuticle.
500: Explain how thorax deformation in indirect flight produces wing beats (which muscle action results in wing downstroke vs. upstroke).
500: Contraction of dorso-longitudinal muscles shortens the thorax front-to-back, causing the notum to deform and the wings to rise or fall depending on linkage; contraction of dorsoventral muscles flattens or arches the thorax, producing the opposite stroke—together thoracic deformation drives wing oscillation at high frequency.
500: Compare the Gliding Theory and the Surface-Skimming Theory and explain why scientists favor Surface-Skimming as a precursor to flight.
500: Gliding Theory posits passive gliding from elevated surfaces leading to powered flight; Surface-Skimming suggests proto-insects used wing-like structures to generate thrust/ lift while skimming water surfaces. Surface-Skimming is favored because experimental and biomechanical evidence shows small flapping surfaces can generate thrust on water and fossils show adaptations consistent with skimming more readily than controlled gliding.
500: Define acclimation in the context of insect cold tolerance and explain how acclimation affects mortality rates when insects are exposed to low temperatures.
500: Acclimation is the physiological adjustment to gradual temperature change (e.g., cold hardening). Acclimated insects often show lower mortality at a given low temperature compared with non-acclimated individuals because of induced protective biochemical and structural changes.
500: Describe the difference between obligatory diapause and facultative diapause, and name the main environmental factor that influences diapause timing.
500: Obligatory diapause occurs every generation as a fixed part of the life cycle (not dependent on environmental cues). Facultative diapause is induced by environmental cues (photoperiod, temperature) and may be skipped in favorable conditions. The main factor influencing diapause timing is photoperiod (day length), though temperature and other cues can modulate it.