BARK-LICE. 



BARK-LICE. 



bark is suffered to touch the ground ; and it is, 

 perhaps, upon the whole, the best practice in 

 all seasons and situations. 



BARK-LICE. The mischiefs effected 

 through these minute insects, to fruit and other 

 valuable trees, are far greater than is generally 

 supposed, and hence every farmer and gar- 

 dener must be interested in becoming inti- 

 mately acquainted with the nature and habits j 

 of so formidable an enemy. For the following ! 

 exceedingly interesting account of bark-lice 

 commonly met with in the eastern states, we 

 are indebted to our eminent countryman, Dr. 

 Thadeus William Harris of Massachusetts, 

 who was employed by that extremely liberal 

 and enlightened state to write an account of 

 the " Insects Injurious to Vegetation" and made 

 his report to the legislature in 1841. His 

 treatise upon the subject forms a large octavo 

 volume of 460 pages. 



" The celebrated scarlet in grain, which has 

 been employed in Asia and the South of Eu- 

 rope, from the earliest ages, as a colouring 

 material, was known to the Romans by the 

 name of Coccus, derived from a similar Greek 

 word, and was, for a long time, supposed to be 

 a vegetable production, or grain, as indeed its 

 name implies. At length it was ascertained 

 that this valuable dye was an insect, and others 

 agreeing with it in habits, and some also in 

 properties, having been discovered, Linna-us 

 retained them all under the same name. Hence 

 in the genus Coccus are included not only the 

 Thtla of the Phoenicians and Jews, the Kermes 

 of the Arabians, or the Coccus of the Greeks 

 and Romans, but the scarlet grain of Poland, 

 and the still more valuable Cochenille of 

 Mexico, together with various kinds of bark- 

 lice, agreeing with the former in habits and 

 structure*. These insects vary very much in 

 form ; some of them are oval and slightly con- 

 vex scales, and others have the shape of a 

 muscle ; some are quite convex, and either 

 formed like a boat turned bottom upwards, or 

 are kidney-shaped, or globular. They live 

 mostly on the bark of the stems of plants: some, 

 however, are habitually found upon leaves, 

 and some on roots. In the' early state, the 

 head is completely withdrawn beneath the 

 shell of the body and concealed, the beak or 

 sucker seems to .issue from the breast, and the 

 legs are very short and not visible from above. 

 The females undergo only a partial transforma- 

 tion, or rather scarcely any other change than 

 that of an increase in size, which, in some 

 species indeed, is enormous, compared with 

 the previous condition of the insect ; 'but the 

 males pass through a complete transformation 

 before arriving at the perfect or winged state. 

 In both sexes we find threadlike or tapering 

 antennae, longer than the head, but much 

 shorter than those of plant-lice, and feet con- 

 sisting of only one joint, terminated by a single 

 claw. The mature female retains the beak or 

 sucker, but does not acquire wings ; the male 

 on the contrary has two wings, but the beak 

 disappears. In both there are two slender 

 threads at the extremity of the body, very short 

 in some females, usually quite long in the 

 .males, which moreover are provided with a 

 18 



stylet at the tip of the abdomen, which is re- 

 curved beneath the body. 



" The following account drawn up by me in 

 the year 1828, and published in the seventh 

 volume of the 'New England Farmer,' p. 186, 

 187, contains a summary of nearly all that is 

 known respecting the history and habits of 

 these insects. Early in the spring the bark- 

 lice are found apparently torpid, situated lon- 

 gitudinally in regard to the branch, the head 

 upwards, and sticking by their flattened infe- 

 rior surface closely to the bark. On attempt- 

 ing to remove them they are generally crushed, 

 and there issues from the body a dark co- 

 loured fluid. By pricking them with a iiiu, 

 they can be made to quit their hold, as I have 

 often seen in the common species, Coccus hes- 

 peridum, infesting the myrtle. A little later the 

 body is more swelled, and, on carefully raising 

 it with a knife, numerous oblong eggs will be 

 discovered beneath it, and the insert appears 

 dried up and dead, and only its outer skin re- 

 mains, which forms a convex cover to its 

 future progeny. Under this protecting shield 

 the young are hatched, and, on the approacu 

 of warm weather, make their escape at the 

 ml of the shield, which is either slightly 

 elevated or notched at this part. They then 

 move with considerable activity, and disperse 

 themselves over the young shoots or leaves. 

 The shape of the young Coccus is much like 

 that of its parent, but the body is of a paler 

 colour and more thin and flattened. Its six 

 short legs, and its slender beak are visible 

 under a magnifier. Some are covered with a 

 mealy powder, as the Coccus cacti, or cochenille 

 of commerce, and the Coccus adoniduin, or 

 mealy bug of our green-houses. Others are 

 hairy or woolly; but most of them are naked 

 and dark-coloured. These young lice insert 

 their beaks into the bark or leaves, and draw 

 from the cellular substance the sap that nou- 

 rishes them. Reaumur observed the ground 

 quite moist under peach-trees infested with 

 bark-lice, which was caused by the dripping 

 of the sap from the numerous punctures made 

 by these insects. While they continue their 

 exhausting suction of sap, they increase in 

 size, and during this time are in what is called 

 the larva state. When this is completed, the 

 insects will be found to be of different magni- 

 tudes, some much larger than the others, and 

 they then prepare for a change that is about to 

 ensue in their mode of life, by emitting from 

 the under-side of their bodies' numerous little 

 white downy threads, which are fastened, in a 

 radiated manner, around their bodies to the 

 bark, and serve to confine them securely in 

 their places. After becoming thus fixed they 

 remain apparently inanimate ; but under these 

 Jifeless scales the transformation of the insect 

 is conducted ; with this remarkable difference, 

 t that, in a few days the large ones contrive to 

 j break up and throw off, in four or five flakes, 

 I their outer scaly coats, and reappear in a very 

 similar form to that which they before had; 

 the smaller ones, on^ the contrary, continue 

 | under their outer skins, which serve instead 

 of cocoons, and from which they seem to 

 ; shrink and detach themselves, and then be- 

 M 2 137 



