4 CLASSIFICATION OF THE ALEYEODID^E. 



day after emergence), and continued, averaging four per day for eleven days, 

 rersonal observations were here discontinued, but E. A. Back, an undergraduate 

 student at the Entomological Laboratory, noted that the adult died Jan. 1, 

 1}:)03. 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 vrere 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 iu the same pot. Egg laying began March 

 IS. 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 iu another pot. By an 

 j-ccident 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 5'oung reached maturity, the 

 adults being males without exception. 



To summarize these observations, unfertilized eggs hatch and the larvae 

 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 iu the adult con- 

 dition for twenty-three and more than thirty-six days respectively. 



I haA'e 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 ai"e 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 sexes of 

 Aleyrodcs in nature, based on actual count of eighty-five specimens of adult 

 Aleyrodcs taken at random, representing four different species. The figures 

 given were twenty males to sixty-five females. For the purpose of obtaining a 

 more exact idea of the proportion of the sexes in the present series I counted 

 one hundred adults taken at random, and found twenty-three males to seventy- 

 seven females. 



Morrill and Back^ have further established the phenomenon in 

 Aleyrodes citri and it is not improbable that it will be found to 

 occur in many species. 



