106 THE SPRING GRATN-APHIS OK " GREEN BUG. 



Walton, of this bureau, observed a larva, taken from the body of a 

 " green bug," to apparently feed upon another larva of the same species 

 that was resting against it. Tins would seem to indicate a tendency 

 toward cannibalism. The parasites have been observed apparently 

 ovipositing in aphidids that were already dead from parasitic attacks, 

 those killed by fungus, and sometimes even puncturing the leaves 

 of the plants on which Toxoptera were located. 



The period of oviposit ion varies from 3 days to a week or more, 

 depending upon the temperature. In warm weather the females will 

 easily live and oviposit for 5 or 6 days. 



LENGTH OF PERIOD FROM EGG TO ADULT. 



Messrs. Kelly and Urbalins found that at Wellington, Kans., from 

 7 to 15 clays are consumed in passing from egg to adult during 

 August and September, while for October and the first week in 

 November it requires from 8 to 24 days. These figures are to a slight 

 degree artificial, as the rearings upon which they are based were 

 conducted indoors. The room was heated by a stove, during the day 

 only, for a part of October and November, and all fire was extin- 

 guished at night, so that the temperature at night probably went 

 almost as low as out of doors, the house being only a small two- 

 room structure. 



The average for August and September is 11.1 days; the average 

 for October and November (first week) is 19 days, the average for 

 the whole period being 15.9 days. These averages were made up from 

 observations on 116 individuals and are therefore of more value 

 than they would be if made from a few individuals only. 



At Richmond, Ind., the period from egg to adult out of doors varies 

 from 10 to 14 days during August and September, while Toxoptera 

 that were parasitized during November of 1907 and kept out of doors 

 did not give up adults until the 27th and 28th of March and the 4th of 

 April, 1908, a period of over 4 months. 



EFFECT OF PARASITISM BY APHIDIUS UPON DEVELOPMENT OF HOST. 



It has been found, as previously stated, that at no time from birth 

 to and including the adult stage is Toxoptera exempt from attack by 

 Aphidius. It appears that a female Apliidius prefers to oviposit in 

 Toxoptera of the second and third instars. The parasite apparently 

 shows little or no fear of them at this stage, while if she is among a 

 number of adult Toxoptera and they begin to kick up their abdomens, 

 she often hurries away, apparently in alarm. 



It appears from our observations that Toxoptera stung before the 

 first or second molt will not reach maturity, nor will the developing 

 parasite become adult, there being apparently insufncent nourish- 

 ment contained in such small individuals. Aphidids parasitized after 



