13 



from other insects, and even the two sexes of the same species are 

 much unlike. The females pass the greater part of their life 

 entirely motionless on trees and shrubs ; nothing in their exterior 

 would lead one to suppose them insects. When mature and ready for 

 laying eggs the scale appears rather as an excrescence of the tree. 

 The males at one stage are lively and active, but have then only a 

 single pair of wings, and no organs for procuring food. The mouth 

 parts disappear during the metamorphosis of the insect, and a second 

 pair of eyes appears in their place. The female is always sluggish and 

 wingless, and in the adult the body is generally scale- or gall-like, or 

 grub- 1 ike and clothed with wax. Though the body of the larval 

 female is ringed and bears legs, all trace of segmentation is usually 

 lost later. Among the Coccidce are found many of the most serious 

 pests of the horticulturist and agriculturist ; scarcely any kind of fruit 

 tree is free from their attacks. The numerous species described from 

 Jamaica by one of the former Curators of the Museum, who made a 

 speciality of this group, is evidence of their great abundance in this 

 island, whilst almost daily specimens are still sent to the Museum for 

 examination. During recent years much attention has been paid, more 

 especially in America, to devising methods for destroying and check- 

 ing the pests ; the insecticides which are now most widely used being 

 alkaline washes and kerosene emulsions. 



Perhaps the scale of greatest concern at present to us in Jamaica is 

 the Mussel-scale, Mytilaspis citrieola, affecting the oranges ; more 

 particularly in the lower, drier parts of the island. It is not rare 

 around Kingston, and I have received oranges affected with it from St. 

 Ann ; but, in the higher orange growing districts of the island, as at 

 Mandeville, it does not appear to be very prevalent. In its structure 

 and life-history it exhibits some most remarkable conditions and may 

 be taken as representative of the group. 



The scale in the stage we are most familiar with is a minute brown 

 mussel-shaped body, about one-eighth of an inch long, flattened on 

 its adhering surface, but convex on the other ; a slight margin of 

 lighter, less dense material is present. If turned over and exa- 

 mined with a lens it is seen to be either a dead hollow chamber with 

 a partial, membranous floor, or else to contain small eggs irregularly 

 arranged The manner in which this condition is brought about is 

 one of the most striking processes in insect life. For what follows we 

 are indebted mainly to the researches of the American entomologists. 

 Starting with the eggs laid by the mother we find that they undergo 

 development, producing minute creatures, mere specks, scarcely distin- 

 guishable to the untrained eye. The newly hatched scale insect is 

 oval in outline, much flattened, furnished with six legs, a pair of an- 

 tennre, and an apparatus for sucking the juice from plants. After 

 wandering about for a time, usually a few hours or even less, the 

 young insect settles on some part of a plant, inserts its beak, and 

 drawing nourishment from the tissues, commences its growth at the 

 expense of its host. In a short time there begins to exude from the 

 body of the larva fine threads of wax, which are cottony in appearance. 

 Sooner or later the larva begins to excrete a pellicle, which, although 

 very thin, is dense and firm in texture. The mass of cottony fibres 

 either melts or is blown away. After a period the larva sheds its 



