Sciara is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of fungus gnat

Fungus gnat

Fungus gnats are small, dark, short-lived flies, of the families Sciaridae, Diadocidiidae, Ditomyiidae, Keroplatidae, Bolitophilidae and Mycetophilidae , sometimes placed in the superfamily Mycetophiloidea, whose larvae feed on plant roots or fungi and aid in the decomposition of organic matter...

s that feed on decaying organic matter and fungi, and are often found in greenhouses. Their larva

Larva

A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...

e are up to 6 mm long, white, slender and legless, with a black head and smooth semi-transparent skin which reveals the contents of the digestive tract.

The adult fly is small, up to 3 mm, has a dark brown body, small head and its legs

Arthropod leg

The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa , trochanter , femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus ,...

 and wings

Insect wing

Insects are the only group of invertebrates known to have evolved flight. Insects possess some remarkable flight characteristics and abilities, still far superior to attempts by humans to replicate their capabilities. Even our understanding of the aerodynamics of flexible, flapping wings and how...

 are comparatively long, looking like a mosquito

Mosquito

Mosquitoes are members of a family of nematocerid flies: the Culicidae . The word Mosquito is from the Spanish and Portuguese for little fly...

.

Sex determination in sciara is a different mechanism. Sciara basically has 4 pairs of chromosomes 3 pairs of autosomes and one pair of allosomes. Some special chromosomes called limited chromosomes are present in certain stages.

The zygote has 3 pairs of autosomes a one or more limited chromosomes and 3 X chromosome (2 fathers’, 1 mother's).

There are 2 stages in Sciara

1) GERM LINE

Is also the gametic line where the gamete formation takes place. The no. of chromosomes
during this line is different in males and females.

i) MALES

In the formation sperms the 1st spermatocystic division is monocentric mitosis, the maternal
and paternal homologous chromosomes are separated. Then few limited chromosomes are eliminated
not all of them. After this one paternal X chromosome is also eliminated. Hence male germ line
(spermatogonia) cells have 3 pairs of autosomes, 2 (one maternal and one paternal) X
chromosomes and a few limited chromosomes.

ii) FEMALES

In the formation ova the 1st ovarian division is monocentric mitosis, the maternal and
paternal homologous chromosomes are separated. Then few limited chromosomes are eliminated not
all of them. After this both 2 paternal X chromosome are also eliminated. Hence female germ
line (oogonia) cells have 3 pairs of autosomes, 1 maternal X chromosomes and a few limited
chromosomes.

2) SOMA LINE

Is the vegetative stage. During early cleavage stages of the embryo limited chromosomes
are eliminated. The no. of chromosomes during this line is different in males and females.

i) MALES

During the 5th and 6th divisions of the embryo all the limited chromosomes are eliminated.
Then paternal X chromosome is eliminated which are 2 in number. Hence male soma line cells have
3 pairs of autosomes and one maternal X chromosome.

ii) FEMALES

During the 5th and 6th divisions of the embryo all the limited chromosomes are eliminated.
In the next stage of cleavage one paternal X chromosome is eliminated. Hence female soma line
cells have 3 pairs of autosomes and one maternal and one paternal X chromosome.