220 



FOREST ENTOMOLOGY. 



badly infested with "brown scale." For example, a comparatively 

 small specimen of Croton will often serve the purpose. In order to 

 understand the structural details, it is best to prepare and mount 

 a young adult, and examine it under the inch objective. It is then 

 advisable to carefully look for all the characters found in fig. 210. 

 In the first place, see the mouth and sucking-tube, as at a and b. 



The antennae (fig. 211) should be 

 well studied, as the number and 

 relative lengths of the joints often 

 afford important points in classifica- 

 tion. At c c c c we get the openings 

 leading to the spiracles or stigmata, 

 and these structures may be carefully 

 studied. At d we find the anal 

 plates or lobes ; at e the anal cleft ; 

 and at / the marginal spines. All 

 these structures are clearly displayed 

 in the young adults. The legs, like 

 the antennae, should also be care- 

 fully noted under the field of the 

 microscope. 



But while the microscopist thus 

 gains a general idea of the struc- 

 ture, the fully developed "brown 

 scale" is nevertheless a puzzling- 

 organism to the practical man. 

 Perhaps it may be best understood 

 by adopting an illustration. In 

 view, therefore, of making it in- 

 telligible, it is to be hoped that a 

 very homely, if not grotesque, 

 simile may be used. Most people 

 are conversant with the tortoise a 

 creature moving along with short legs and hard body. Now suppose 

 this creature was born with fully developed legs, but after one or two 

 " moults " the body developed, say, fifty times its infantile size, while 

 the legs remain the same as at birth, and also as a natural consequence 

 the creature became absolutely helpless from such abnormal develop- 

 ment, we should have exactly an analogous case to the development 



Fig. 210. Adult female Lecanium after 

 treatment with potash X 20. 

 a, mentum ; b, rostral filaments, forming 

 the sucking-tube ; ccce, ventral chan- 

 nel leading to spiracles ; d, anal plates 

 or lobes (dorsal) ; e, anal cleft ; /, mar- 

 ginal spines. (From Newstead's 'Mon- 

 ograph of the British Coccida}.' Ray 

 Society.) 



Fig. 211. 



-Typical antenna of female 

 Lecanium. 



