Ant colonies > Internal structure of ants > Muscular system

Muscular system

The Muscular System

For an account of this system in ants the reader must be referred to the articles of Janet, Nassonow, Berlese and Lubbock, as the subject is one of too great complexity and detail to be treated within the limits of this work. Still there is a11 ontogenetic change in the muscular system of the adult queen ants, which cannot be passed over, as it is of no little ethological importance. I have often observed that aged, dealated queens will float when placed in water or alcohol, and that when the thorax of immersed specimens is pierced with a needle, large bubbles of air escape, showing that the wing muscles must have atrophied.

Janet (1906, I907a, 1907b) has studied the histological changes, which lead up to this peculiar condition in Lasius niger, and finds that the muscles, which in the virgin queen fill up most of the thoracic cavity and are well-developed and beautifully striated till the marriage flight occurs, are completely broken down within a few weeks after dealation (Fig. 26). He maintains that this sarcolysis is not due to phagocytes devouring the muscles piece-meal, but that the blood corpuscles ( amoebocytes ) which creep in among the fibrillae take up spontaneously the dissolving muscle substances and convert these within the cytoplasm into fat globules and albuminoid granules. Thus the amoebocytes become adipocytes and replace the muscle fibrillae (Fig. 26, B)

Somewhat later the amoebocytes discharge the fat globules and albuminoid granules from their cytoplasm into the blood plasma, which from being a limpid liquid assumes a more granular appearance as it becomes charged with more and more of the metabolized products of sarcolysis. Eventually nothing remains of the muscles but their sheaths, and the thoracic tracheae become greatly enlarged, which accounts for the floating of the insect in liquid and the emission of air bubbles when the thorax is pricked under water (Fig. 26, D ) The fatty and albuminoid substances derived from the histolyzed wing-muscles are carried in the blood to the abdomen, where they are taken up by the

FIG. 26. Wing muscles of Lasius niger queen, to show their degeneration after nuptial flight. (Janet.) A, Sagittal section of thorax and petiole of queen immediately after nuptial flight ; B, ten months later; C, transverse section through mesothorax on day of nuptial flight; D, same five weeks later; m, longitudinal vibratory muscles; n, transverse vibratory muscles ; b, blood coagulated and charged with the products of muscle dissolution ; t, tracheae.

ovaries and, no doubt, contribute greatly to the growth of the eggs. The queen ant thus resembles the salmon, in which, according to Miescher, there is at the time of sexual maturity a conversion of part of the trunk musculature into substances that are appropriated by the reproductive cells and further their growth and maturation.