36 APPLE-TRUNK BARK-LOUSE — EGG-PARASITE, LARVA. 



Under these scales I have also repeatedly met with a small 

 maggot, three hundredths of an inch long, or frequently much 

 smaller, of a broad oval form, rounded at one end and tapering 

 to an acute point at the other, soft, of a honey-yellow color, 

 slightly translucent and shining, with an opake brownish cloud 

 in the middle, produced by alimentary matter in the viscera, and 

 divided into segments by faintly impressed transverse lines. This 

 is probably the larva of some minute Hymenopterous insect, spe- 

 cially designed by Providence for destroying the eggs of the bark 

 louse. That these eggs are its food is shown by the fact that 

 when the maggot is small a number of eggs are found under the 

 scale with it, when it is larger the eggs are fewer. The indivi- 

 dual from which the above measurement and description was 

 drawn, had but two eggs remaining for it to consume. Whether 

 the maggot be larger or smaller it, with the eggs, appears to com- 

 pletely fill the cavity beneath the scale, and I have only met 

 with this parasite upon thrifty trees, where each scale had a large 

 number of eggs beneath it. It doubtless remains beneath the 

 scale during its pupa state, and then makes it exit by perforating 

 a small round hole through the scale. Scales which are thus 

 perforated may frequently be met with. Our cut represents a 

 scale magnified and perforated for the escape of a parasite, the 

 short line on the right hand side of the figure indicating the 

 natural length of the scale. 



The eggs are somewhat less than the hundredth part of an inch 

 in length; they are of a regular oval shape, about twice as long 

 as broad, smooth but not shining, opake, most of them of a white 

 color, others dull pale yellow. 



As early as the 12th of May I have found individual larvae 

 hatched, and running about with much activity among the eggs, 

 but remaining under the scale for protection. It is not till about 

 a fortnight later that the eggs mostly become hatched, and the 

 young crawl out from under the scale and scatter themselves over 

 the bark. To the naked eye they appear like minute white dots, 

 uniformly diffused over the smooth bark of the twigs, and ap- 

 pearing like natural white points or glands of the bark. A per- 

 son to whom I once pointed out these white specks was reluctant 



