The race of A. quadrimaculatus in our insectary colony of this species has now been maintained for at least seven years. We have no means of knowing the actual number of generations that have been passed in this artificial environment, but, assuming, what we regard as the conservative estimate of on the average one generation per month, the present tenants of the insectary are at least 84 generations removed from their wild progenitors. During this period there has been no introduction, from any source, of new stock.
It appeared desirable to ascertain whether in this interval there had been any change in the susceptibility of the insectary race to the McCoy strain of P. vivax, which has been propagated in our service during the same period. For purposes of the comparison there were employed wild female A. quadrimaculatus caught in diurnal resting places at the head of the Wacissa river (Jefferson County, Florida) about one-half mile from the site where the progenitors of the colony were secured.