CURRANT AXD GOOSEBERRY APHIDS IN MAINE. 55 



Mymis ribis Linn. 

 Figs. 12, 14. 15, 33, 41. 



It is no uncommon thing to find currant leaves puffy with 

 reddish or yellowish blister-like deformations such as are shown 

 in Fig. 33. These are the home of Mysus ribis, a delicate little 

 aphid not so serious in its work as varians because it attacks 

 directly only the leaves but still troublesome enough to interfere 

 with the proper functioning of the leaves, cause premature 

 ripening of the fruit, and as one currant grower in the State 

 puts his complaint against this species : "though the fruit holds 

 on, the plants are hurt to a certain extent and look very annoy- 

 ing." 



The stem-mother, or form hatching from the over-wintering 

 egg, attains its growth in Maine about mid-May. This insect 

 is very pale green with bright green spots in two longitudinal 

 rows on the dorsal surface. Like the other apterous forms 

 and nymphs the stem mother is rather thickly beset with capi- 

 tate hairs shaped like minute pins with the points attached to 

 the body. 



The immediate progeny of the stem-mother are apparently 

 partly winged and partly wingless, since I have taken colonies 

 as early as j\lay 20 containing the stem mother surrounded by 

 nearly mature apterous forms and pupae. The apterous 

 females, pupae and nymphs of this species are ordinarily pale 

 clear lemon yellow though sometimes nearly water white, and 

 these small pale insects would have to be Yevy numerous to be 

 found if it were not for the telltale danger signal of reddish 

 puffs which give evidence of their presence. 



Both winged and Avingless females are to be found on currant 

 as late as mid-July, the winged forms migrating from time to 

 time to the summer food plant. AMiat this alternate food plant 

 is is not known, for although this species is of practically world- 

 wide distribution and has been recognized as a currant pest for 

 a century and a half it has managed to elude detection during 

 the summer residence. 



The winged form when freshly molted is a clear pale lemon 

 yellow. Later the dorsal surface of the head, the thoracic lobes 



