Saturday, August 10, 2013


Halloween Pennant

Phylum -              Arthropoda                        Arthropods        
Class -                 Insecta                               Insects
Order -                 Odonata                            Dragonflies, Damselflies
Suborder -           Anisoptera                        Dragonfly
Family -                Libellulidae                       Skimmer
Genus -                Celithemis                         Pennants
Species -             eponina                             Halloween Pennant

This individual was found perched at midday in a field of low-lying vegetation that was in the vicinity of a pond.  Like most members of the Skimmer family The Halloween Pennant is a percher that takes to flight in order to capture passing prey from the air.  Its primary diet is of small, flying insects.  Its legs enable it to better grasp its food and devour its meal while still in flight.  Its very large compound eyes give it a nearly 360o field of view with blind spots only directly behind and beneath its head.  Its vision is like a mosaic and it is sensitive to color that extends into the ultraviolet range. 

The Halloween Pennant ranges from the Gulf coast of the southern United States into the northern latitudes of southern Canada.  The 30o C temperature needed for flight can be achieved by vibrating, or shivering, its powerful flight muscles, generating heat when the air temperature is otherwise too cool to fly.  In addition, the species’ dark coloration enables it to absorb sunlight, passively raising its body temperature.  Dragonflies that inhabit hot, desert climates are generally pale in color because the animal now needs to reflect sunlight in order to prevent becoming overheated as well as to reduce the chance of drying out from evaporative cooling.  Small animals potentially lose water at a faster rate than large animals because their surface area is larger compared to their volume.  Heat is more readily absorbed and the rate of water loss increases.  A waxy layer beneath the insect’s cutaneous shell is believed to aid in water retention.  Still the animal must shed heat by transporting water to its surface through a system of special glands that lead to ducts that emerge from the shell. 

The strongest fliers among the insects are usually those that have evolved to have only two winds, such as certain species of flies, and those whose front and hind wings are locked together, effectively becoming a single wing – as is the case with bees.  Weaker insect fliers suffer the inefficiency of hind wings beating in the turbulence created by the movement of the forewing.  Grasshoppers are an example of this.  The grasshopper’s clumsy flight supplements the power of their hind legs to add distance to their jump.  Dragonflies also have four distinct wings but remain powerful fliers.  They have reduced turbulence by having the hind wing’s beat precede that of the forewing.  Their aerial predatory life style requires that they retain four independently controlled wings in order to achieve their extraordinary flight maneuverability.  Besides having a fast forward speed dragonflies are able to move in reverse direction, hover, and fly straight up or down while keeping their body in a horizontal axis.  They can also change their direction in the seeming space of a dime.  They've sacrificed little in speed in order to achieve an acrobatic mastery of three dimensions.

The Halloween Pennant is a Skimmer, the largest of the dragonfly families.  It hunts from a stationary perch but spends much of its time in flight when mating.  Males may attempt to mate with dragonflies of other species but females seem able to discriminate between species type and are able to refuse males.  Males behave aggressively towards other males when competing for females, fulfilling their role in natural selection.  Males of territorial species compete for habitats most favorable to dragonfly eggs and nymph development.  Depending on the species a dragonfly can spend anywhere from a single season to up to a couple of years in an aquatic environment prior to becoming a terrestrial adult.  During this period mosquito larva can account for a large part of their diet.  They are themselves preyed upon by fish, frogs and water fowl.

Biology Topics:


Eukaryotic Cell

Limited Male

Opportunistic Bacteria

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