Uglogical

In at least two races of lizards there appear to be no males at all,and young are evidently produced from unfertilized eggs. Such reproduction is known as parthenogenesis, or virgin birth. The most familiar case of parthenogenesis is that of the honey bee. The queen lays two kinds of eggs, some fertilized, some unfertilized. The unfertilized eggs produce the males, or drones; the fertilized eggs produce the workers. Ants, wasps and various other invertebrate animals sporadically or periodically reproduce by parthenogenesis. In some cases the parthenogenetic stage occurs at a time when conditions in the environment would make it difficult for the two sexes to meet for mating. How the two lizards evolved the practice, and why, is not clear. In some other species of lizards the females greatly outnumber the males and it is possible that this same phenomenon of parthenogenesis may normally alternate with bisexual reproduction.

Because the genitalia of male reptiles are internal, it is not always easy to tell the sexes apart. It takes a real expert, for instance, to determine the sex of a snapping turtle or alligator. However, in most species there are certain external features by which it is possible to distinguish the sexes of fully mature individuals. The two most obvious ones are size and coloration. There is no set rule about which sex may be the larger, but in many species it is the male that is bigger than the female. Where difference in color patterns exist, it is generally the male which has the more vivid coloration, as is usual in birds; but here again the situation is sometimes reversed. In some species the sexual coloration is a sort of nuptial dress, assumed for breeding and later abandoned.

Internal fertilization is a cooperative process, and to bring it about the sexes must find each other, and must be physiologically prepared for mating. Most if not all reptiles show some sort of courtship behavior by which the sex of a potential partner is determined, the coyness of the female is overcome, and a readiness to mate is generated in both members of the pair. Courtship often duplicates or blends with the expressions of rivalry and home defense between males, and since this whole complex of innate behavior is a hereditary part of the make-up of a species, it affords an interesting field for study.

The courtship of a number of different snakes and lizards is a case in point. Although there are clear similarities in behavior patterns among the two groups, it has been found that most lizards recognize the female visually, while snakes depend on odor, trailing the female with their noses as well as with the tongue and Jacobson’s organ. Male lizards put on quite a display among themselves – showing colored throat fans, erecting crests, arching their necks and affecting various gaits – but how much of this actually carries over into courtship is not surely known. Some of it, however, is brought to bear by the male on a prospective partner. When the female is thoroughly recognized as a female and her reticence overcome, the male lizard (like the males of some snakes) seizes her with his jaw, bends the base of his tail downward to maneuver the cloacal openings into contact, and insertion of one of the hemipenes is affected.

Turtles both aquatic terrapins and land tortoises, carry out varyingly elaborate courtships which may include butting and nipping of the female by the male, or his swimming backward in front of her, fluttering his claws beside her face, or stroking her cheeks with his elongate fingernails. Among some species of pond turtles and among sea turtles, courtship is accompanied by competitive behavior among males.

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