5 



COCCID^], OR SCALE INSECTS. 



By. T. D. A. Cockerell, F.Z.S., F.E.S Curator of Museum, Institute of Jamaica. 



The Coccidce constitute a very well-defined family of the order Hemiptera. They are related to the 

 Aphides, the Cicada, the Phylloxera ; and also, but more distantly, to the plant bugs, such as Dysdereus 

 (the cotton-stainer) and Blissus (the chinch-bag). Nearly five hundred species are known, living on a 

 great variety of plants. Some infest the leaves, some the twigs, others the bark, while certain kinds 

 are found underground on roots. Some are naked, others clothed with a mealy secretion, others 

 covered with wax, while very many construct a well-defined scale ; it is to the latter that the name 

 scale-insect is more properly applied. The females have a beak, whereby they extract nutriment from 

 plants ; when adult they usually become entirely stationary and unable to move, and very many 

 species lose their legs and antennas. At m time do any of the females possess wings. 



The males, on the contrary, are winged in nearly all the species, and well able to move about. 

 They have legs and antennas, but no beak; their wings are two in number, after the manner of flies, 

 thus totally differing from all other Hemiptera, which have four wings. 



There is an allied family, the Aleurodidce, which might be confounded with the Coccidae, and 

 indeed was in former times. When immature they resemble scale-insects, and the adults look not 

 unlike the males of Coccidae. But an examination at once reveals differences ; both sexes are winged, 

 and there are four wings instead of two. In Kingston, species of Aleurodes are common on pepper 

 ( Capsicum ) and lignum-vitae. 



Another insect resembling a Coccid is the Cerataphis latanue, which, as the generic name in- 

 dicates, is really one of the plant-lice {Aphides). Mr. Campbell sent me specimens from Castleton 

 Gardens, found on a palm ; and since then I found it quite commonly on a palm in the yard of the 

 Museum, in Kingston. It looks something like an Aphis, but is surrounded by a beautiful white 

 waxy fringe. 



Destructiveness of THE CoCCIDiE. 



Professor Comstock, in his excellent report on Scale-Insects published in the Report of the U. S. 

 Department of Agriculture for 1880, writes — 



" There is no group of insects which is of greater interest to horticulturists to-day than that 

 family which includes the creatures popularly known as ' scale-insects' and ' mealy bugs.' There is 

 hardly any shrub or tree but that is subject to their attack , and in certain localities extensive 

 orchards have been ruined by them. The minute size of the creatures, the difficulty of destroying 

 them, and their wonderful reproductive powers, all combine to make them the most formidable of the 

 pests of our orchards and ornamental grounds. It is only necessary to cite the mealy-bugs of green- 

 houses, the oyster-shell bark-louse of the apple, and the various species of scale-insects destructive to 

 citrus-fruits to establish this fact." 



This was written with reference to the United States, but may be taken as applying with even 

 greater force to tropical countries, where the Coccidae are apparently much more abundant. The 

 amount of damage done in any particular case is not always easy to estimate, from various causes. 

 Thus, in the case of the coccanut, it is probable that those who have attributed the death of the palms 

 to Coccidae have over-estimated the influence of these insects, since we now know from the researches 

 of Dr. Plaxton and Mr. Fawcett that the cocoanut is subject to the attacks of fungous and 

 bacterial parasites, and the probability is, that the scale-insects in this instance only hasten the end 

 inevitable from other causes. On the other hand, I believe the damage done is frequently under- 

 estimated. When a tree or shrub is dotted all over with scales, behind every one of which is an insect 

 living on the sap, the drain on the resources of the plant must be considerable, In the case of small 

 plants, as for example a capsicum attacked by Diaspis lanatus (n. sp.), death may speedily ensue; but 

 trees as a rule survive the injury, and finding that they continue to live and bear fruit, we are apt 

 not to reflect that they would do better if protected from the attacks of insects. In order to ascertain 

 accurately the influence of insect pests on any kind of tree, it would be necessary to take several 

 growing in the same locality, and carefully spray some, while neglecting the others. If this were 

 carried on for a number of years, no doubt the difference to be observed would be very marked ; anl in 

 the case of very seriously attacked plants, it would be a difference between living and dead. 



It may be objected, that a drain on the vegetative tissues of a tree is not necessarily harmful; as 

 we are obliged frequently to check exuberant growth by pruning : but to this it can be replied, that 

 the purpose of pruning is not so much to check the energies of the plant, as to divert them to the 

 production of flowers and fruit ; while the Coccidae attack not only the fruiting branches, but the fruit 

 itself, injuring the very parts we desire to protect. 



Mr. Bowrey and other observers have noted that weakly plants are those usually attacked, strong 

 ones escaping. It would often be difficult to prove this, as if the facts are stated another way, namely 

 that the plants attacked are weakly, we have but a truism. Nevertheless, it is apparently well-ascer- 

 tained that plants suffering from other causes do especially harbour scale insects, and in uny case it is 

 perfectly evident that given the same amount of insect-injury in any two cases, the plant which was 

 also injured in some other way would soonest die. 



As an instance of the severe way in which some plants are attacked, we may take the genus Citrus, 

 which includes the orange, lemon, &c. These trees are attacked in America by four or five species of 

 Aspidiotus, one Chionaspis, one Parlatoria, two of Mytilaspis, two of Ceroplastes, one Dactylopius 

 (mealy-bug), one Icerya, and three of Lecaniwn. Of these 11 citrus-scales, eleven appear to be f jund 

 in Jamaica, though not all as yet on Citrus. 



The special injury done by the several species will be discussed later on. 



