4 CLASSIFICATION OF THE ALEYKODIDJS. 
day after emergence), and continued, averaging four per day for eleven days. 
Personal observations were here discontinued, but E. A. Back, an undergraduate 
student at the Entomological Laboratory, noted that the adult died Jan. 1, 
1903. On Jan. 7 I found the plant dead, apparently from cold, and on examina • 
tion of the leaves I found that about three-fourths of the eggs had hatched, 
and that some of the larvae were in the second instar at the time the plant died. 
Quite a number of eggs were found that had certainly been laid during my 
absence, but they were not counted. , 
4. March 17, 1903, a female emerged from its pupa case, and was isolated 
on tomato and chickweed growing in the same pot. Egg laying began March 
18. Eggs were deposited on the stems and upper and lower surface of the 
leaves of both plants, making it impossible to count from day to day all the 
eggs that had been laid. On April 2, forty-nine eggs were counted, and on 
April 22 eighty more were known to have been added to this number. There 
were about eight days altogether when the female was in such a position on the 
plant that no attempt was made to count the eggs for fear of disturbing her. 
At a very low estimate, twenty-five eggs were laid during these days. The 
offspring of this female began to emerge as adults on April 22, and the original 
female was transferred to a chickweed plant growing in another pot. By an 
accident I lost on the same day the positive identity of this insect, but I am 
quite sure that she produced the forty-nine eggs which I counted on April 29, 
after which observations on this insect were discontinued. So far as observed, 
all the eggs laid by this female hatched and the young reached maturity, the 
adults being males without exception. 
To summarize these observations, unfertilized eggs hatch and the larva? 
develop into adults of the male sex. Two females were known to lay forty- 
four and one hundred and twenty-nine eggs respectively, and in both cases 
many more were undoubtedly laid. These same insects lived in the adult con- 
dition for twenty-three and more than thirty-six days respectively. 
I have tried several times to isolate a female which had certainly been 
impregnated, but was unsuccessful. It is not impossible to do this, however, 
and I suspect that when this is done the young produced from fertilized eggs 
will all develop into females, giving us a condition similar to that which is 
generally believed to occur in the honey bees, and known as arrhenotoky. 
In regard to the length of adult life, I might further add that in green- 
houses where there are millions of live adults on the plants, it is difficult to 
find a single dead specimen on the benches, providing they have not been killed 
by artificial means. This is a further indication that natural deaths among 
adults are rare, and that the adult life of each individual may extend over 
many weeks. 
Should it prove true that unfertilized eggs of this insect produce only males 
and fertilized eggs only females, then the number of adult males and females 
will be in direct proportion to the number of unfertilized and fertilized eggs. 
In Psyche (April, 1903) I gave an estimate of the proportion of the two sivv.es of 
Alcyr<j<l<s in nature, based on actual count of eighty-five specimens of adult 
Aleyrodes taken at random, representing four different species. The figures 
given were twenty males to sixty-five females. For the purpose of obtaining a 
more exacl idea of the proportion Of the sexes iii the present series 1 counted 
one hundred adults taken at random, and found twenty-three mules to seventy- 
seven females. 
Morrill and Back 6 have further established the phenomenon, in 
Aleyrodcs citri and it is not improbable that it will be found to 
occur in manv Bpecies. 
