NO. 12 ADAPTATIONS TO SOCIAL LIFE — SNYDER 7 



SEX 



At certain seasons of each year, winged sexual, colonizing forms 

 appear in well-established termite colonies, these forms having color 

 in the body and having eyes. Normally termites shun the light, 

 but these forms are impelled by some irresistible impulse to leave 

 the parent colony and become markedly positively phototropic — a 

 reversal of only temporary nature. As is necessary, the colonizing 

 flight, or " swarming," is often correlated with rainfall, especially in 

 arid regions. The lower termites have a longer, stronger flight and 

 emerge from the parent colony in smaller numbers and at irregular 

 intervals, while the more specialized species are restricted to a few 

 large flights annually. The line of weakness at the base of the wings 

 (where the wing breaks off after the flight) in the lower termites is 

 often poorly defined, but is well defined in the higher termites which 

 sometimes lose the wings in mid air, whereas the lower termites 

 are forced to pry off the wings after alighting. In some genera the 

 sexes are markedly attracted to each other before and after the flight 

 or '' swarm." The wings are lost and the males and females 

 now exhibit marked thigmotropism ; they burrow under pieces of 

 decayed wood lying on the ground, under the bark on dead trees, 

 logs or stumps, and in arid regions under dry cow chips, stones, etc. 

 Mating does not take place while the insects are in the air and not 

 until they have separated into pairs and together excavated a small 

 " royal cell " and have fed on wood or cellulose in another form. 

 Then the sex organs have matured and are ready to function. 



The act of coition is not by superimposition ; Haviland, not having 

 observed coition, thought that the relatively small male must fertilize 

 the eggs after they had been laid by the huge Termes queen ; a Vermes 

 queen with markedly distended abdomen measures loo mm. in 

 length, 22 mm. in width and 20 mm. in height — the male is 16 mm. 

 in length, 4 mm. in width and 3 mm. in height. However, super- 

 imposition in coition is unnecessary, since the sexes mate with the 

 apices of the abdomens opposed. Termites again differ from all the 

 other social insects in the continued cohabitation with and fertiliza- 

 tion of the female by the male. Such repeated fertilization is neces- 

 sary, due to the enormous number of eggs laid in large colonies. 



Hence it has been noted that termites in the course of their speciali- 

 zation have lost the strong power of flight, for it is no longer 

 necessary to seek "mates" afar, when they swarm in enormous 

 numbers. The queens lose their power of locomotion after a slow 



