Life Cycle of the Mosquito (1946)

[Music] la of all the blood sucking insect pests which plague mankind the mosquito is among the most pernicious mosquitoes are divided into two great tribes the anophelines some of which transmit malaria assume this position in biting and the cusines which may spread yellow fever Deni and fasis bite in this position the mosquito body is divided into three parts the head thorax and abdomen the thorax Bears three pairs of legs and a single pair of wings the head Bears the eyes the fers or antenni the palpy and the beep the abdomen Bears no special structures except the reproductive organs in the female the antenna are fringed with short hairs rising from the edge of each segment while in the maale the antenna are conspicuously tufted with large whs of hair The prominent antenna are the chief distinguishing features of the male a mosquito bites primarily to obtain food as a female settles down to a blood meal her beak appears to Bend at the middle actually the beak consists of a jointed protective sheave that bends while a thin lanp enclosed within this sheath pierces the skin a crosssection of the beak shows that this Lancet consists of six separate stylets which enclose between them two tubes one for saliva and one for blood a small amount of the insect saliva is injected into the wound to prevent clotting of the blood which is then sucked up as food the abdomen swells perceptively as the blood meal progresses a male mosquito cannot bite or suck blood a newly emerged male may try blood suction without success the beak of the male is not constructed to pierce human or animal skin male mosquitoes feed exclusively on vegetable juices the nectar of flowers the juice of fruits the female also feeds on vegetable juices but blood forms the major part of her diet some mosquitoes lay eggs on the surface of water some near the water some mosquitoes like shaded water others sunlit some require fresh water others prefer salt but all mosquitoes require water of some kind floodwater mosquitoes lay their eggs singly in mud near water or in other areas which later may be covered with water the eggs of floodwater mosquitoes can remain dormant sometimes for years until the conditions of warmth and water are suitable for hatching floodwater mosquitoes living in regions having cold Winters over winter in the egg stage a section of frozen mud taken from a swamp where floodwater mosquitoes are known to breed in summer when immersed in water at room temperature will cause mosquito larv to appear a few days later most other mosquitoes overwinter in the adult stage such hibernating adults can be found in Hollow trees in culverts under houses porches or in cellers these mosquitoes lay eggs fitted with two floats on the surface of the water or in large buoyant masses called egg boats except when overwintering mosquito eggs hatch into larv soon after they are laided sometimes in less than a day the mosquito larva after hatching is usually whitish or gray in color floating at the surface of the water it inhales air through its breathing tube it soon molds shedding the original the laral skin emerging somewhat larger into the second instar or period of laral development in the same way the larvae passes through the third and into the fourth and last instar the Lara has no legs or other organs of locomotion and moves by a series of jerks or Wiggles in some species the body of the larvae is transparent and the Heart action may be observed as in all insects the contraction waves begin posteriorly and Advance anteriorly watch closely this tail-to-head pulsation the head and thoracic segments of the larvae are enlarged sometimes twice as broad as the abdominal segments the abdomen is divided into nine segments the first seven of which resemble each other closely and differ little in species on the ninth segment are the anal gills on the eighth segment tube through which the larvae breathes most larv hang head down with the breathing tubes at the surface of the water the anop larvae however lies horizontally when feeding at the water surface examined closely the mouth parts are seen to be in constant motion the anop larvae which can turn its head 180° to facilitate feeding sets up currents at the water surface with its mouth brushes to bring within range the floating particles on which it feeds when the larvae has reached the fourth instar appendage buds which will later grow into the legs and wings can be seen on the ventral side of the thorax through the semi-transparent cuticle in the second instar these appendage buds while already differentiated are not yet well enough developed to be visible at this point of growth full grown the Lara now Begins the change through the pupil form telescoping its body slightly it commences to shed its cuticle usually beginning at the head for a while the insect May rest its new pupil head projecting from its larvel body finally with a few convulsive jerks the laral cuticle complete with breathing tube is cast off and the mosquito assumes a new gu that of a puper in this stage no food is taken although the body remains in water the pupa has its head and thorax punched into one Mass with no obvious organs except two black spots which will later become eyes and two horn-shaped appendages at the top of the thorax which serve as breathing tubes the abdomen terminates in two swimming paddles which Propel the pupa through the water as the pupa grows older the wing pads become recognizable folded up against the wing pads are the cases of the long jointed legs of the adult the pupil stage is shortlived lasting usually only 1 to 4 days in warm weather when the adult is fully developed within the pupil case the pupa is less active it tends to straighten out and takes on a shining glittering appearance suddenly the skin bursts along the middle of the back the adult Rises up almost vertically literally oozing out of the pupil envelope the wings are first fre finally the long legs are carefully extended to support the fully developed body in a few minutes the drying process is complete the insect is now ready to fly with this final transformation there has evolved The Familiar adult mosquito the mosquito is an excellent example of an insect undergoing complete metamorphosis the egg the larvae the puper and the adult truly the female of the species is more deadly than the male [Music]