II. Life cycle

Дата канвертавання24.04.2016
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According to their mouth parts, flies may be classified into: 1) piercing and sucking type - blood sucking, Glossina (tsetse flies), stable flies, gadflies (horse flies) and gnats (black flies); 2)sponging and lapping type - this type is much more important in China.

According to their habit, they may be divided into wild and house frequenting. The house-frequenting is more important. There are 5 families of lapping flies which are important to human health. All of them belong to the order Diptera:

-Muscidae, -Calliphoridae, -Sarcophagidae, -Oestridae and -Anthomyiidae

Features of a lapping fly: antenna 3 segments, 3rd segment is big and club-shaped with an arista on the base of the 3rd segment. The longitudinal veins of the wing are all unbranched.

I. Morphology

Musca domestica vicina: 90-100% of flies in houses belong to M. domestica. M. domestica domestica is found in south China. M. domestica vicina is found in Doth south and north China.

Adult - median sized, 6-7mm in length (female larger), dusky gray and covered with fine hair. Head: A pair of compound eyes, three ocelli, one pair of antennae and one proboscis. Thorax: Mesothorax is well-developed, with four longitudinal dark bands on the dorsal surface. The 4th longitudinal vein bends abruptly up-wards, nearly meeting the tip of the 3rd vein. One pair of claws and one pair of pulvilli on each leg. Abdomen: Male with 8 segments and female 9, first and second fused. Only 5 segments are visible. The anterior half of dorsum of abdomen is orange yellow, posterior half dusky gray. The ventral abdomen is yellowish. Egg: Banana-shaped, creamy white, I mm in length.Larva: Light yellowish. A mature larva is about 12 mm in length. No eyes. The anterior end is pointed, posterior end is blunt. Pupa: Brownish, 6-7 mm in length.

II.Life cycle

Complete metamorphosis, with the exception of Sarcophaga which lay larvae instead of eggs.

Egg--1 day--larva (3 stages)--30℃ 5 days--pupa--3-4 days-- adult

9-12 days after emergence, female flies begin to lay eggs. One female house fly may lay 2,000 eggs in her life. There are 7-8 generations in a fly season. The life span of an adult is about 6-8 weeks.


1.Study the general characteristics of common house flies and different stages in the life cycle.

2.study the relationships between the morphology of flies and transmission of disease.

IV. Individual observation

Adults and eggs of body lice and pubic lice.


Lice are dors0ventrally flattened, relatively small, wingless insects, which have three pairs of stout legs, each ending in a tarsal claw. The mouth parts have adapted to sucking host's blood and cutaneous juices. They are exclusively ectoparasites of mammals. Lice have partial metamorphosis--egg, nymph, and adult. They spend their entire life on their hosts.

Human lice consist of three types: (1) head louse, Pediculus humanus var. capitis; (2) body louse, P. h. var. corporis; and (3) pubic or "crab" louse, Phthirus pubis. P. humanus var. capitis is at present a hybrid breed. Lice play a twofold role in the production of disease in man: (1) body lice, and to a lesser extent head lice and pubic-lice, transmit louse-borne typhus fever, trench fever, relapsing fever, and other diseases from man to man; (2) lice produce an irritating dermatitis (pediculosis).


Adults (body lice and pubic lice):

1. Body louse, slide specimen: observe under low power. Grayish white in color, dorsoventrally flattened, wingless; female larger than the male. Head: rectangular-ovoidal from dorsal aspect, a pair of eyes spots, a pair of five-jointed antennae (anterior to the eye spots), mouth parts of piercing type, hidden in the head when not in use. Thorax: three pairs of strong legs provided with claws adapted for clinging to hairs or fibers. Abdomen: the abdomen of the male is narrower than that of the female and is rounded posteriorly.In the female the terminal segment is inverted V-shaped.

2. Head louse, slide specimen: dark grayish, smaller than the body louse.

3. Pubic louse, slide specimen: crab-like, distinctive in appearance.


Study the general characteristics of body louse and pubic louse.

III. Individual observation

Adults and eggs of body louse and pubic louse.

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