In this essay we will discuss about House-Fly. After reading this essay you will learn about:- 1. Habit and Habitat of House-Fly 2. External Structures of House-Fly 3. Inner Structures 4. Life History 5. Control.
Essay Contents:
- Essay on the Habit and Habitat of House-Fly
- Essay on the External Structures of House-Fly
- Essay on the Inner Structures of House-Fly
- Essay on the Life History of House-Fly
- Essay on the Control of House-Fly
1. Essay on the
Habit and Habitat of House-Fly:
The house-flies are daytime visitors of human habitations specially with non-hygienic conditions. The open drains, garbages, kitchen and pantries are the favourite residing and breeding places of the house-fly. The house-flies have special fascination for sitting on hanging or stretched ropes and wires.
At night innumerable flies are seen to be sitting on such ropes and wires. The house-fly, being smart and agile, gives frequent flying visits to other parts of the house and sits over uncovered foods. Such visits bring various germs with its body and contaminate human foods.
2. Essay on the External Structures of House-Fly:
The grey coloured body has yellowish tinge on the ventral side. The dorsal side of the thorax has four elongated lines (Fig. 18.86). The abdomen possesses a single streak on the mid-dorsal line. As in other insects, the body of house-fly consists of three tagmata—head, thorax and abdomen.
A. Head:
The head of the house-fly is small and semi-circular in outline. A pair of much prominent compound eyes each containing nearly 4000 ommatidia and three small simple eyes or ocelli are present. The appendages include the Antennnae and mouth parts. The antennae are paired, short and flexible.
The distal segment of the antenna is the largest one which contains a brush-like arista. The mouth parts are well developed and facilitate in its peculiar way of feeding.
The type of mouth parts found in this animal is called spongin type which contains two portions:
(a) Proboscis and
(b) Food channel.
The proboscis, formed by the fleshy and retractile labium, may be separated into three parts:
(i) Basiproboscis or rostrum,
(ii) Mediproboscis or haustellum and
(iii) Distioproboscis or labellum.
The rostrum carries in front a pair of maxillary palps. The middle part is movable and powerful. The last part is extended as a pair of membranous oval and spongy oral lobes or labella, which is traversed by numerous channels, called pseudotracheae, opening externally along the margin. All these pseudotracheae open distally in a single aperture, called the mouth.
The mouth is situated at the tip of the next part known as food channel. The food channel is formed by the participation of labrum, epipharynx and hypopharynx. The notable feature in the mouth parts of house-fly is the absence of mandible, the function of which is taken up by rows of teeth like serrations in the under-surface of oral lobes.
B. Thorax:
Three segments are not clearly demarcated in this tagma, which bear three pairs of legs and two pairs of wings. Three pairs of walking legs have typical insect-like divisions. The terminal end of each leg is provided with a pair of curved claws. In between the curved claws lie a pair of glandular pads, called pulvillae, having numerous hollow hairs.
Through these hairs a sticky substance comes out which helps in walking. Numerous hairs and bristles occur throughout the surface of the legs. There are specialised sense organs in the tarsus of each leg. When these tarsi come in contact with sweet water the proboscis protrudes out.
Of the two pairs of wings, only the anterior pair is prominent, broad, transparent, hairy and triangular. The posterior pair is modified into stick-like halters which work as sensory and balancing organs. When at rest, the wings fully cover the abdomen, and during flight they vibrate rapidly to produce a typical sound. In the adult males, the ability to fly lasts only for 2 weeks.
C. Abdomen:
It is oval, hairy and segmented. In females there are nine segments but the males have eight. In the females, four segments from the 7th to 10th participate in the formation of retractile ovipositors for laying eggs. In males, the last four segments form a genital pouch and other associated structures.
3. Essay on the Inner Structures of House-Fly:
The muscular system specially, the flight muscles, are well developed. The flight muscles constitute the 11% of its body weight. The alimentary canal is long and carries distinct diverticulum and crop. The crop is believed to have sucking ability. The respiratory system is represented by 10 pairs of spiracles, longitudinal tracheal trunks and their segmental branches.
A pair of large dilated base in the abdomen is known as aerostats. Of the ten pairs of spiracles, the eight pairs of abdominal spiracles are simple in construction. The two pairs of thoracic spiracles are specially modified and are supposed to act as sound producing organs. The network of tracheae has reduced the haemocoelomic space.
Such spaces are confined near the wing muscles and are filled up with blood containing carbohydrate and other reserve fuels. The function of excretion is carried out by four elongated Malpighian tubules. The fusion of thoracic segments has led to the condensation of nerve cord.
Mechanism of feeding:
It ingests liquid food. The solid foods like sugar are moistened by its saliva and are taken in a dissolved state. During ingestion the fly extends the proboscis and immerses the labella within the food.
The pseudotracheae of the labella are filled up with the liquid food by capillary action. The sucking action of muscular pharynx draws the food inside the food channel. The crop is filled up with large volume of food, which enters to the mid gut slowly.
4. Essay on the Life History of House-Fly:
Copulation continues for a couple of minutes. The male grasps the dorsal side of the female with the help of pro- and mesothoracic legs. The female fly inserts its ovipositor within the genital atrium of the male.
A week after copulation the female fly starts laying eggs. After one copulation, eggs are laid in 5 or 6 batches, each consisting of 100-200 eggs. For the laying of egg it requires a medium containing sugar, protein and water. With the help of its ovipositor the female fly digs organic manures, debris, decaying fruits and vegetables. The white eggs are elongated and have curved dorsal thickening.
The eggs hatch within 8-24 hours and a larva, called the maggot or gentle, comes out of the egg by making an elongated slit on the dorsal side. Sometimes the hatching is completed immediately after the laying of egg. The maggot is white and 2 mm in length. Its anterior end is narrower than the posterior end. There is no sign of head, legs and wings in the maggot.
The body is divisible into thirteen segments, of which the anterior segment is rudimentary and contains two oral lobes. Each oral lobe has two sensory tubercles and a number of branched food channels. The mouth is placed between the two oral lobes. On the interior end of the mouth, there is a hook-like mandibular sclerite which also helps in locomotion.
Each segment from sixth to twelfth possesses semilunar spiny structures, called seminiferous pads, on its ventral side. These are structures for locomotion. On the mid-dorsal position of the twelfth segment, a pair of D-shaped spiracles communicates with the inner tracheal trunk.
In course of its rapid growth, the larva moults twice and a pair of fan-shaped spiracles develop on the dorsal side of the third segment. The maggot after its full growth contracts and enters into the stage of pupa. A hard case is formed around the body from which only the spiracles remain projected outwards.
Inside the covering rapid change takes place. Except the nervous system all the larval structures are broken down by a process, called histolysis. New structures are formed from special groups of cell, called imaginal discs.
When fully formed, the young fly forces open a lid at the anterior end of the pupal case and come out. The newly emerged fly is colourless and with rudimentary wings and short legs. But within a short period, swelling and elongation of different parts occur. Thus the individual becomes transformed into an adult.
5. Essay on the Control of House-Fly:
The house-flies endanger human life by contaminating foods and drinks with germs of various diseases. These germs come along with its body and also with the excreta and regurgitated products of the flies. All preventive measures adopted against the house-fly are two-fold—against the adult fly and against the larvae and maggot.
(i) Against adult flies:
The flies prefer filthy places, thus it is necessary to maintain general cleanliness in and around the houses. The uses of insecticides specially the use of poisonous threads help to reduce the number of flies. But most important is to keep all the foods and drinks under cover so that the flies may not sit over it.
(ii) Against larvae and maggot:
The house flies can only be eradicated properly by taking measures against its larvae and maggot. The favourite breeding places of the fly should be cleaned and treated with insecticides. It must be remembered that the measure which is adopted against adult fly can produce more significant result if taken against its breeding places.