Charlotte St. Romain
1991 Woodrow Wilson Biology Institute
Pin the insect to the wax by placing 1 pin through the head and another through the base of the abdomen. Caution! Be sure the pin in the base is placed way off the midline. The heart is in the midline lying just beneath the cuticle on the dorsal side of the insect. Although the tube heart is quite sturdy, pinning may cause damage to the structure.
With sharp-pointed scissors, make two longitudinal incisions along the side of the cricket's cuticle. Make the incisions from the base of the abdomen to the top of the abdomen. Once the abdomen is open be sure to cover it with insect saline so that the heart does not dry out. Carefully, cut across the cuticle between these two cuts at the top of the abdomen and cut the flap off. You will now be able to see yellow malphigian tubules which will be actively moving about the body cavity. Observe their movement, then carefully lift them and cut them out.
The female is distinguished from the male by the ovipositor or egg layer. The male has different shaped wings. If it is a female, remove the ovaries/oviducts before you try to see anything else. Sometimes the ovary is broken and many eggs are released into the body cavity. The eggs are whitish capsules which can obscure and compress all the other organs. The eggs can be removed by simply washing the body cavity with saline solution.
The force necessary for moving blood through the organism is provided by musculature associated with the major tube of the circulatory system. In open systems, muscle provides the force to move blood or fluid back into the major tube, which is referred to as the heart, for redistribution to the body. Such hearts in insects contain ostia which are opened by alary muscles creating the force for fluid movement into the heart. Sequential alary muscles beat such that a wave-like contraction is observed along the heart. The movement of this "peristaltic" wave is from the tail of the insect toward the head. Determine the respiratory rate which generally ranges from about 10 to 20 abdominal contractions per minute, and the heart rate which generally ranges from about 90 to 120 beats per minute. The heart is a thin, almost transparent tube visible through the intersegmental membranes along the mid-dorsal region.
With the alimentary tract in place note the peristaltic movements, the coiling of the hind gut, and the connections of the tracheae. Grasp the esophagus with a forceps and cut just anterior to that point. Slowly lift the anterior end of the alimentary canal, carefully cutting the tracheal connections until only the rectum is connected.
Wodring, Joseph, "Internal-external morphology of the house cricket." LSU, Baton Rouge.