Essay on House-Fly | Insects

In this essay we will discuss about house-fly. After reading this essay you will learn about: 1. Introduction and Economic Importance of House-Fly 2. External Features of House-Fly 3. Life-History 4. Preventive Measures.

Essay # Introduction and Economic Importance of House-Fly:

The common house-fly is scientifically known as Musca domestica. The body is grey with yellowish tinge on the ventral side. Four elongated lines are seen on the dorsal side of the thorax and a single streak is present on the mid-dorsal line of the abdomen.

These flies are notorious for carrying the germs of various diseases. This they do by carrying microbes through the external and internal parts of their body from garbage, etc., to the foods and drinks of the human beings.

Essay # External Features of House-Fly:

In the characteristic fashion of insect the body is divided into three parts—head, thorax, and abdomen.

Head:

Semicircular in outline with two very large compound eyes. Three simple eyes or ocelli are placed on the dorsal side. Head contains following appendages.

1. Antennae—one pair, short and flexible. The distal seg­ment is the largest and contains a branch called artista.

2. Mouth parts—arranged in a fashion to facilitate its mecha­nism of feeding. This type of mouth parts is called spongin type, which includes two structures (a) Proboscis, and (b) Food channel. Man­dibles are absent and maxillae are represented only by a pair of maxillary pulps.

(a) Proboscis:

It is formed by the labium and is fleshy and retractile.

The proboscis may be separated into three parts:

(i) Basiproboscis (basal part),

(ii) Mediproboscis or haustellum (middle portion), and

(iii) Distioproboscis (distal part).

The middle part is strongly built and movable. The distal part is extended as a pair of membranous, spongy labellae. The labellae are traversed by nume­rous channels opening externally through the margin.

(b) Food Channel:

It is formed by the union of pseudo-trachae and consists of three parts—labium, epipharynx, and the hypo­-pharynx. Two styles persist, but are incapable of piercing.

Thorax:

Divisions are indistinct. Mesothorax is larger than pro- and metathorax. Three pairs of walking legs and one pair of wing are the appendages in the thoracic region.

Walking Leg of House-Fly:

Consists of usual divisions of insect leg. A pair of curved claws are present in the terminal end of each tarsus. A pair of glandular pads, pulvillae with numerous hollow hairs are present between the claws. A sticky juice is secreted from these hollow hairs which help them in walking.

Wing of House-Fly:

Presence of one pair of wing is the feature of this order. The second pair of wing is modified with a stick-like structure called halters, which act as sensory and balancing organ. The wings are broad, transparent, hairy and triangular. During flight the wings are vibrated rapidly and a sound is produced by them.

Abdomen:

Oval, hairy and segmented (8 in male and 9 in female). First and second segments are much reduced. In the female flies seventh to tenth segments serve as retractile ovipositors.

Mechanism of Feeding:

Lives only on liquid foods. Solid foods like sugars are moistened by its saliva. At the time of feeding the fly extends its proboscis and sets the labella on the food. The pseudo-trachae on the labella get filled with food by capillary action id finally it is drawn through food channel by the sucking action of the muscular pharynx

Essay # Life-History of House-Fly: (Fig. 116):

Reproduction takes place by copulation, which lasts only for a few minutes. Male grasps the female on her dorsal side with the help of its pro- and mesothoracic legs. The female fly inserts its ovipositor within the genital apparatus of the male and the male structures aid in the entrance.

After fertilization, the female fly begins to lay eggs. Eggs are generally laid on organic manures, debris and decaying fruits and vegetables. A single fly lay a large number of eggs at one time. The eggs are white and elongated, carry a curved thickening on its dorsal side. The hatching takes place within 8-24 hours and the process is temperature dependent.

Larva is called maggot. It is white and elongated with anterior end narrow and posterior end broad. Head, legs and wings are absent. The body is divided into one anterior segment and twelve trunk segments. The anterior or cephalic segment is rudimentary and contains a pair of oral lobe.

The oral lobes are provided with sensory ‘oral tubercles’ (2 in each lobe) and a number of branched food channels. Mouth is present in between the two oral lobes. A hood-like mandibular sclerite is present on the anterior side of the mouth and helps only in locomotion.

From sixth to twelfth segment, there are pad-like structures on the ventral side, called seminiferous pads. These help in locomotion. A pair of spiracle is present on the mid-dorsal position of the twelfth segment, which opens into the trachae. The larvae feeds on liquid food and grows rapidly. It sheds its skin twice (the process is called moulting) and gradually develops a pair of fan-shaped spiracles.

After certain period, the full-grown maggot contracts and passes into the next stage called pupa. A hard case is formed around the body from which only the spiracles remain projected outwards. Within the pupal skin, rapid transformation takes place.

Old organs excepting nervous system are replaced by new, which are formed by special groups of cells called imaginal discs. Young fly comes out of the pupal case after knocking the anterior end like a lid.

A newly grown fly differs much from a full-grown fly in having colourless body, rudimentary wings, short legs. But within half of an hour swelling and elongation of different parts take place and it transforms into an adult one.

Essay # Preventive Measures against House-Fly:

As the microbes carried by these flies endanger human lives, great care must be taken to prevent the contamination of foods and drinks by these flies.

Following measures are usually recommended:

1. To observe cleanliness in and around house.

2. To keep all the foods and drinks covered, so that flies cannot sit on it.

3. To use different insecticides for killing the maggots and the adult.