In this article we will discuss about the dissection of blue bottle fly. Also learn about:- 1. The Alimentary System 2. Dissection of Nervous System.
Blue bottle flies can be easily collected from fruit markets of any town or city.
Killing:
The flies can be killed with chloroform within a very short time.
Dissection:
Fix the freshly killed specimen (Fig. 7.1) in a dorsal position on a paraffined petri dish with entomological pins, passing through the abdominal sterna and coxa of legs. Cut the lateral membranes (pleura) between the terga and sterna of both the sides of the thorax and abdomen with a pair of fine scissors.
Posteriorly the two incisions should meet at the hindmost end of the abdomen. Proceed anteriorly up to the anterior border, of the thorax. Give a transverse incision along the anterior border of the first thoracic tergum.
Carefully remove the terga and the thoracic and abdominal cavities are exposed. Fix the head of the fly on the paraffin of the petri dish by pushing pins through two sides of the head capsule. Cut the eye and adjacent tissue of one side of the head to expose the anterior part of the oesophagus and salivary glands. Put clear water in the tray.
The Alimentary System:
Partially uncoil the intestine and push the alimentary canal (Fig. 7.2) to one side and prevent its coming back to the initial position by pushing a pin on the petri dish.
Mouth:
The labium forms a short proboscis which terminates into two pads. The surface of each pad is chambered by grooves called pseudo-tracheae.
Oesophagus:
It is a narrow tube. Arising from the proboscis it runs upward and then backward, piercing through the brain. In the anterior part of the abdomen the oesophagus bifurcates.
Proventriculus:
One of the branches of the oesophagus joins with a globular bag-like structure, the proventriculus.
Ventriculus:
It is a long, muscular bag, the anterior end of which joins with the proventriculus. Posteriorly it continues as the intestine.
Food reservoir:
The other branch of the oesophagus runs straight up to the anterior one- third of the abdomen and forms a blind sac with two lobes, the reservoir.
Intestine:
It is a coiled tube with a slightly dilated anterior portion. The intestine has two distinct zones—the proximal and hind intestine. Two pairs of Malpighian tubules open in the hind intestine.
Rectum:
A pyriform, muscular chamber provided with four papillae.
Anus:
A narrow round aperture at the posterior end of the rectum.
Salivary glands:
A pair of long, tubular glands located ventrally in the thorax and the head (Fig. 7.2). The glands open at the base of the proboscis through a narrow duct.
Dissection of Nervous System:
The nervous system in blue bottle fly is simple.
Fix the head and rest of the body of the fly in a dorsal position on a paraffined petri dish with entomological pins. Carefully remove the epicranial plate of the head to expose the cerebral ganglia. Expose the thoracic and abdominal cavities. Cut the oesophagus, anterior to the brain and pull it out. Remove the intestine and the viscera, and the nervous system (Fig. 7.3) is exposed.
Cerebral ganglia or brain:
The two cerebral ganglia and the infra-oesophageal ganglia are fused to form a compact mass. It bears a perforation through which the oesophagus runs. The two optic stalks sending nerves to the eyes are quite large and lie against the anterolateral sides of the brain. Nerves from the ganglionic mass innervate antennae and mouth parts.
Ventral nerve cord:
The double chain ventral nerve cord is short and connects the thoracic and abdominal ganglionic mass with the ganglionic mass formed by the fusion of cerebral and infra-oesophageal ganglia.
Thoracic and abdominal ganglionic mass:
The thoracic and abdominal ganglia are fused to form a large ganglionic mass situated in the anterior part of the thorax. The ganglionic mass sends three pairs of nerves to the thoracic legs.
Posterior nerves:
A large abdominal and a few Small nerves arise from the posterior end of the ganglionic mass. The abdominal nerve innervates the abdomen.