The Eyes of Dactylopius. 



By 

 Frederick H. Krecker. 



(From the Biological Laboratories of Princeton University.) 



With Plate IV. 



In the family Coccidae the adult male, as is well known, presents 

 a very abnormal condition in regard to the number, position and struc- 

 ture of its eyes. On either side of the head there is an eye with a single 

 Cornea; since these are the only eyes possessed by the young n}Tiiphs 

 they have been termed the primary eyes. In the adult, in addition 

 to the primary eyes, there are two pairs of eyes, one pair on the dorsal 

 aspect of the head, and the second pair on the ventral aspect; these 

 have been termed the accessory eyes. 



It is commonly stated that the ventral pair of accessory eyes oc- 

 cupy the position of the mouth parts, which are said to be wanting in 

 the adult. 



With the hope of throwing some light on this remarkable feature 

 in the metamorphosis of these insects, a study of the structure of the 

 ventral accessory eyes was undertaken. Since the common mealy-bug, 

 Dactylopius destructor, was the most available species it was selected 

 for the purposes of this study. 



Dactylopius destructor is commonly found in nearly all green- 

 houses and, more often than not, is very abundant. But few plants 

 are free from infestation. The males are not very numerous and in 

 the adult stage are rather hard to find since they live but a short time 

 after reaching maturity. They pass the nymphal period in small cot- 

 tony cocoons which are attached to the under side of leaves. 



Practically nothing has been written concerning the finer details 

 of these eyes. Wliat has been published is mainly the work of the 

 Italian investigators, A. Targioni-Tozzetti and Antonio Berelese, 

 who have described their grosser features with considerable accuracy. 



