306 ME. A. D. MICHAEL ON THE 



This nymph was quite white at first, but gradually became 

 larger and a little darker. 



On the 2nd of May the nymph changed its skin. The cast skin 

 did not show any trace of plates, and was quite white, except 

 that there were a few chitinous dots or cells scattered about it, 

 each having a darker nucleus. A few of these cells had approached 

 certain others in little groups, where they had begun to assume a 

 hexagonal or pentagonal form : these cells could not be distin- 

 guished on the living creature, but only by examining the cast skin. 



The nymph, after the change of skin, did not then show any 

 trace of detached dorsal plates. It continued to get larger and 

 darker up to 15th May, but still did not show dorsal plates. 



On 15th May the nymph again changed its skin, and became a 

 perfect male ; it was, as usual, rather light at first, but gradually 

 acquired the full hardness and darkness of the adult species, which 

 is wholly dark and chitinous. 



Although the nymph up to the last did not exhibit any dorsal 

 plate, yet on examining the cast skin two dorsal plates were clearly 

 visible with a space between them ; they were, however, so much 

 lighter and thinner than in Gamasus coleoptratorum, that when 

 on the creature they could not be distinguished as plates at all, 

 but only as a slight darkening of the surface. The cellulation 

 was quite different from that of the dorsal plates of G. coleoptra- 

 torum, being composed of more equal-sided hexagonal or penta- 

 gonal cells irregularly placed, and each cell appearing to be formed 

 of smaller granules. 



I bred several other specimens, the times being nearly identical 

 from the hatching of the eggs. All the eggs first laid, and which 

 I knew, because I removed them and placed them in separate 

 cells, turned out to be males, all the later laid eggs turned out 

 females. The times occupied by the changes from hatching to 

 attaining the adult form were about the same in the females as 

 the males, and there was the same apparent absence of dorsal 

 plates. 



I did not get any perfect females until about a month after the 

 first males had emerged ; but of course it is highly probable that, 

 under natural conditions, more eggs might have hatched and a 

 larger proportion been reared ; and thus the females might have 

 followed more closely on the males; 



These females had the single dorsal plate detached from the 

 sternal plate, and showing the white membranous line between, 



