lu 



rai'ciiE. 



IJan. — I'eb. 18S3. 



of those from the upper side being 

 usually nearly round and smooth (fig. 

 3, a), while those of the under side are 

 more variable in shape and are always 



Fig. 3. Scales of JJoplia coeruUa: a, from elytron ; 

 ^, from under side of thorax; r, from femur; d, fine 

 structure to be seen in a with high powers. Knlarge- 

 ment : a^ b and c^ loodiam.; rf, 5oodi:nn. 



covered with spines or hairs (fig. 3, i 

 and c). The scales upon the legs are 

 most variable of all in form ; common 

 among them are lanceolate forms (fig. 

 3. c), covered with fine hairs. The 

 average size of the scales is about o. 10 

 mm. long by 0.05 mm. wide, and they 

 are attached to the insect by a more or 

 less prolonged basal portion (fig. 3, 

 a-c) ; they lie very flatly pressed upon 

 the surface of the insect. 



Most of the scales of tlie dorsal sm- 

 face of the thorax and of the elytra, 

 when viewed by transmitted light, are 

 bright canary yellow, but many of them 

 are tinged with carmine red. Viewed 

 by reflected light, or upon a dark back- 

 ground, the parts before yellow are 

 bluish, or dark and nearly invisiiile, 

 while all the parts before reddish are 

 now dark and more or less indistinct 

 (or rarely greenish if they were purplish- 

 red before). If the stage of the micro- 

 scope is now revolved, and the light to 



be reflected from the scales is thus 

 brought from a diflerent direction in 

 regard to the scales, some of the parts 

 before dark become bright bluish while 

 others just before blue become darkened, 

 but in no case do parts of a scale which 

 were reddish by transmitted light be- 

 come bluish by reflected light. If the 

 light is not excluded from above the 

 stage of the microscope, when examin- 

 ing these scales by transmitted light, 

 places will be discovered, where the 

 scales are injured or where thev are 

 turned up at their margins, in which 

 bright blue, or rarely green, will be 

 seen. In all cases where I speak of 

 trarismittcd light I have excluded the 

 light from above the stage of the micro- 

 scope, and where I speak of reflected 

 light I have excluded light from below 

 the stage of the microscope. 



If the scales are in any way injured 

 or cracked, is they usually are in re- 

 moving them from the insect, water will 

 readily enter them and discharge the air 

 from them. Scales thus treated with 

 water are, by transmitted light, sky blue, 

 soiuetimes tinged with carmine red, the 

 latter color being in portions of the 

 scales which had not been thoroughly 

 penetrated by the water, for \\ bile the 

 \\ ater is entering the scales the)' become 

 reddish for a time before changing to 

 blue. Hoiling the water a minute 

 causes all red to disappear but seems to 

 iiaxe no fmther action on the scales; 

 their structure is not altered, as the 

 water inside such minute cavities is not 

 readily boiled. By reflecteil light m;mv 

 scales that have been treated with water 

 are dark greenish. 



