65. On the Internal Anatomy of the Male Lac Insect, Laccifer lacca Kerr (Homoptera, Coccidze)
- 1The adult male is a delicate two-winged insect of a crimson colour with a pair of white wings, plumose antenns, and two pairs of dark shining ocellanm. It has three pairs of legs, made up of the usual five segments, of which the tarsus terminates in a claw. The limitations of the three component segments in the thorax are not sharply defined. The thorax carries the wings dorso-laterally, while its ventrum bears the two pairs of spiracular openings and the three pairs of legs. On the dorsal side the mesothorax carries a plate known as the mesotergal sclerite, and the metathorax carries a shield-shaped piece—the scutellum. The abdomen consists of nine or ten segments, of which the last three or four segments fit in closely. Terminally the abdomen carries the male copulatory appendage, the penial style. On either side of this are the caudal pits out of which the white wax-filaments issue forth.
- 2The integument of the male lac insect consists of an outer cuticle underlying which is the synctial layer of hypodermis, in which the nuclei are visible, but cell boundaries cannot be made out. Lac-glands are absent because the male lac insect does not secrete lac in its adult life.
- 3The gut of the male lac insect is of the same nature as that of the larva and the female lac insect. (Esophagus, ventriculus, proximal and distal intestines, colon, colon czcum, and rectum can easily be made out. Salivary glands and Malpighian tubes are also present. The digestive organs are not abortive. A definite anal opening is present dorsally between segments 9 and 10 at the base of the male copulatory appendage.
- 4There is no indication of a pulsatory vessel, and hence the vascular system may be taken to be absent in the male lac insect.
- 5The muscular system of the male lac insect is well developed, and especially so in the thorax, which possesses two median longitudinal muscles, external to which is a pair of slightly oblique longitudinal muscles, which, in conjunction with the former, tend to contract the thoracic cavity. Four bands of oblique lateral muscles are also present in the thorax, These descend with a deep oblique sweep and meet on the median line of the thorax with a broad base. In the abdomen there are the usual sets of segmental longitudinal tergals and sternals, tergo-sternals, and oblique sternal muscles. A few slips of muscles are also present at the base of the antennz and in the cervix.
- 6The nervous system consists of a cerebral and a ventral nerve ganglion connected with the former by means of a pair of connectives through which the esophagus passes. The cerebral ganglion appears in sections to be composed of four lobes, whilst the ventral ganglion betrays itself to be made up of five ganglia. These represent the infra-esophageal, the three thoracic, and the fist abdominal. Histologically there is a cortical layer of deeply staining nuclei and a medullary zone of a homogeneous character. From the brain a pair of antennary and two pairs of optic nerves are given off. whilst the ventral ganglion gives off three pairs of nerves to the legs and some minor nervures from its hind end for the innervation of the internal organs.
- 7There are two pairs of spiracular openings on the thorax. The spiracular opening leads into the collar-chamber, from the base of which the main tracheal trunk arises.
- 8The generative system consists of a pair of long tubular testes, a pair of vasa deferentia, the ductus ejaculatorius, and the external copulatory organ, the chitinised penis. In the adult male the testes are greatly distended with spermatozoa and occupy a great deal of the body-cavity. Histologically the vasa deferent& are made up of an internal epithefial layer resting upon a circular musculs external to which are a few longitudinal muscles. The penial style is made up of two separate curved tubes, one of which is incompletely surrounded by the other. This is very clearly seen in cases of everted penis and is, further, attested by microtomic sections. The spermatozoon has a screw-like head and a filamentous tail. The duration of copulation varies from 10 to 20 seconds.
- 9At the base of the caudal pits wax glands are present. The mouth of the caudal pits is covered with a chitinous plate bearing numerous pores and two or three setae. These pores are the openings of the “nuclear ducts” of the wax glands lying underneath. The white waxy filaments carried by the male lac insect are secreted by these glands. For a fuller discussion of wax glands reference may be made to my paper on the internal anatomy of the larva and the female lac insect (12).
- 10The male lac insect possesses two pairs of ocellanae, one of which is dorsal and the other ventral. Structurally both of them are constructed on a common type of plan. Externally there is the thick cuticular lens internal to which is the retina, which is qualitatively divided into a proximal layer of “rods” and a basal layer of retinal cells proper. The base of this layer is embraced by a prominent and somewhat stout nerve. The ocellanae are innervated by two pairs of nerves arising from the dorsal and ventral sides of the external lobes of the cerebral ganglion.
- 11Prior to the emergence of the male an operculum is formed at the hind end of the resinous cell when the last ecdysis takes place. The rejected skin is ejected from the cell by the caudal strokes of the pupa, and in doing so the operculum frequently gets unhinged from the cell and the opening is left wide open. The male emerges by crawling out of this opening backwardly.
- 12The male lac insect is a very beautiful creature and its life is a chapter of ceaseless activity. The sole mission of its life, apparently, is to provide the females with spermatozoa so as to ensure the future generations of its kind. Its average life lasts from 62 to 91 hours. The presence of the ventral pairs of eyes is undoubtedly of great help to its possessor in finding its way through the felted mass of waxy filaments and in locating the female aperture. The male lac insect is not capable of any distant flight, for it can at best only hop and flutter about. Being light-bodied it is liable to be carried away by strong winds from one spot to another. The winged males have a distinct advantage over the non-winged ones inasmuch as, whilst the former can recover themselves if they happen to fall on their backs the latter cannot do 80 unless they get a mechanical support to take advantage of.