On the Life History and Structure of the Early Stages of Simuliidae (Diptera, Nematocera). Part II
Authors: Puri I. M. 
Published: June 2009

(A) Life History.

(1)Simulium larvaeare found in streams where the current is very fast. They are sedentary in habit and fix themselves to some support by means of their posterior sucker and sticky salivary secretion.

(2) Progression is achieved by looping movements which have been described in detail.

(3) Larvae feed on all kinds of fresh water animalcules, and algae.

(4) Two species were reared from eggs to the adult flies for the first time in the laboratory. Abundance of food and aeration of water are two very important factors governing the rearing of these larvae.

(5) There are six larval stages, each stage lasting 4–7 days. The gradual changes in the successive stages are described inS. erythrocephalumandS. aureum.

(6) The sixth-stage larva, having woven its cocoon, changes into a pupa, the whole process, weaving of cocoon and pupation (described in detail), takes 75–90 minutes. Pupal life lasts 5–15 days, depending on temperature.

(7) The eggs are sub-triangular in form and are laid in large patches on aquatic plants below the surface of water.

(8) The first-stage larva is characterised by the presence of an egg-burster situated dorsally upon the head.

(B) Morphology.

(9) The larvae are eucephalous, with eleven faintly marked body-segments, three thoracic and eight abdominal, the eighth abdominal being apparently divided into two parts, the posterior carrying the anus and posterior sucker. There is a median uniramous thoracic proleg which like the posterior sucker is provided with a number of cuticular hooks.

(10) The head has a number of markings which are of great taxonomic importance.

(11) The head-appendages are: A pair of jointed antennae, a rounded labrum, a pair of lateral fan-shaped appendages (the premandibular organs), a pair of mandibles, a pair of maxillae each with a single-jointed palp, a hypopharynx, and a labium. These appendages have been described in detail in this paper for the first time.

(12) The alimentary canal, malpighian tubules, salivary glands, muscular system and gonads are dealt with in detail.

(13) The oesophageal valve has no blood sinus as has been erroneously described by previous writers.

(14) A pair of dorsal glands are present above the pharynx. Their walls consist of large uninuclear cells. Dorsal glands have so far been found only inSciaraamong Dipterous larvae.

(15) There is a well-developed central as well as visceral nervous system. The bilobed brain lies in the head and a chain of eleven ganglia in the body. Both the supra-intestinal and the infra-intestinal visceral systems are fully worked out for the first time.

(16) There is a well-developed tracheal system with ten closed spiracles, one prothoracic, one metathoracic and eight abdominal.

(17) The flattened dorsal vessel stretches from the seventh abdominal segment to the head where it ends just behind the brain. It is dilated in the seventh segment to form the heart which is provided with two pairs of ostia.

(18) Nephrocytes or excretory cells (pericardial, and peri-oesophageal) are described for the first time and compared to similar structures in other Dipterous larvae.

(19) A detailed description of the early stages of all the known (seventeen)1British species is given, with remarks about eleven of them, as they occur in Sweden, Norway and France.

(20) The characters used for determining the species are as follows:Larva. Head markings; antennae; mandibles; submentum; anal gills; ventral papillae; and posterior sucker.Pupa. Chaetotaxy, Respiratory filaments, and Cocoon.