Aphelinidae 499 



Family aphelinidae 



BREEDING A PRIMARY PARASITE AND TWO 

 HYPERPARASITES OF THE GERANIUM APHID 



Grace H. Griswold, Cornell University 



THE geranium aphid, Macrosiphum cornelli, has proved an ideal 

 host for the breeding of parasites. Unlike many other greenhouse 

 aphids it is present at all times of the year and may easily be propagated. 



Before breeding the parasites might be attempted it was necessary 

 to devise some method of caging that would make conditions entirely 

 satisfactory to the aphids. Geraniums are very susceptible to mildew if 

 the plants are kept under too moist conditions. On the other hand, if a 

 geranium gets too dry, the aphids soon become restless and crawl from 

 the plant. Rearing the insects on growing plants, therefore, did not 

 seem to be feasible. Leaves of the common Lady Washington geranium 

 {Pelargonium domes ticum) will keep fresh for days in water and on 

 leaves so kept the aphids were found to thrive. Although the develop- 

 ment of the aphid is somewhat hastened by this method it is not prob- 

 able that the development of the parasites is abnormally affected. 



The rearing cage finally adopted consists of a glass lamp chimney 

 covered at the top with cheesecloth and set in an earthenware saucer. 

 Although the glass cylinder comes in close contact with the saucer, a 

 strip of cotton batting was kept about the bottom of each cage as an 

 added precaution against the entrance of undesirable animal life. Not 

 only has this cage proved satisfactory to the aphids but it appears to be 

 equally satisfactory to the parasites, which are able to move and fly 

 about in an almost normal manner. A large supply of aphids, free 

 from parasites, was kept on hand in separate rearing cages. 



A certain number of parasite-free aphid nymphs of early instars were 

 exposed each day to the primary parasite for a period of 24 hours or 

 less. Later, if desired, these same aphids were exposed to the hyper- 

 parasites for another and similar period. As soon as the aphids turned 

 black they were removed to small shell vials and carefully labeled. 



Aphelinus jucundus is an internal primary parasite which has been 

 commonly reared from the geranium aphid. It has also been bred from 

 the green peach aphid, Myzus persicae, and from an aphid on rose, 

 Macrosiphum pseudodirhodum. Aphelinus will oviposit in aphids of 

 any stage of development, though the earlier instars seem to be pre- 

 ferred. Hatching occurs in slightly less than 3 days and A. jucundus 

 reaches maturity about 4 weeks after the eggs have been laid. 



Aphidencyrtus inquisitor is an internal secondary parasite. The egg 

 of this hyperparasite is laid within the body of the larva of the primary 



