980 



INSECTS AND ARACHNIDA 



Beck that the scales of a lepidopterous insect belonging to the genus 

 Mormo, which under a low power present the watered-silk appear- 

 ance seen in the Podura scale, under a -1 in. obj. show the 'exclama- 

 tion markings/ whilst under a y 1 ,, in. obj. they exhibit distinct ribs 

 from pedicle to apex, thus showing in one scale how the appearances 

 run from one into the other. 1 



The 'hairs of many insects, and still more of their larvae, are 

 very interesting objects for the microscope on account of their 

 branched or tufted conformation, this being particularly remarkable 

 in those with which the common hairy caterpillars are so abundantly 

 beset. Some of these afford very good tests for the perfect correction 

 of objectives. Thus the hair of the bee is pretty sure to exhibit 



FIG. 728. Test scales of Lepidocyrtiis curvi- 

 collis : A, large strongly marked scale ; B, 

 small scale, more faintly marked. 



FIG. 729. Ordinary scale 

 of Lepidocyrtns curvi- 

 collis. 



strong prismatic colours if the chromatic aberration should not have 

 been exactly neutralised ; and that of the larva of a Dermestes 

 (commonly, but erroneously, termed the ' bacon-beetle ') was once 

 thought a very good test of denning power, and is still useful for 

 this purpose. It has a cylindrical shaft (fig. 730, B) with closely set 

 whorls of spiny protuberances, four or five on each whorl ; the 

 highest of these whorls is composed of mere knobby spines ; and the 

 hair is surmounted by a curious circle of six or seven large filaments, 

 attached by their pointed ends to its shaft, whilst at their 'free ex- 

 tremities they dilate into knobs. An approach to this structure is 

 seen in the hairs of certain Myriopods (centipedes, galley-worms, etc.), 

 of which an example is shown in fig. 730, A ; but a beautiful photo- 



1 Journ. Boy. Microsc. Soc. vol. ii. 1879, p. 810. On the subject generally 

 Dr. A. Spuler's 'Beitrag zur Kemitniss des feineren Baues . . . der Fliigelbedeckung 

 der Schmetterlinge,' in ZooL JaJtrb. Anat. viii. should be consulted. 



