Vol. XXviii I ENTOMOLOGICAL NEWS. 359 



This instar is between three and six days long, hut most took three 

 days. 



The male nymph was distinguishable in this instar by the more point- 

 ed abdomen. 



Fourth (and Last) Nymphal Instar. Antennae noticeably more 

 slender but not so long in proportion; proportional length of joints 

 as before; joints nearly of equal thickness except I and 2 a little 

 stouter, 4 fusiform, pointed, all set with pile and long hairs. Rostrum 

 as before, except that it is more slender and longer, reaching first 

 coxae. The legs are also longer and more slender ; first femora longer 

 and thinner than tibiae, intermediates subequal and hind tibiae slender 

 and longer than femora. In the cast skins the curvature of the hind 

 tibiae of the male begins to be noted. All tarsi are still i-jointed with- 

 out any sign of a suture, although 2-jointed in the adult. Pro- and 

 mesothorax are distinct. Abdomen is much longer, nearly equal in 

 length to the thorax, pointed, male genital segment prominent; general 

 form is oval. 



This instar lasted between four and ten days, the majority molt- 

 ing in 4. This brings the insect to the adult, as noted. 



While emerging from the cast skin in this last molt and directly 

 after, M. borealis is very white with brown markings. The head is 

 tinged with brownish with a white median line; the thorax is whitish; 

 the first and second abdominal segments are brown to within a 

 quarter of their width of the connexivum; the third, fourth and fifth 

 are more narrowly marked, and the 6th and 7th are brown to the 

 connexivum. The connexivum has a brown edge at the inner margin 

 narrowing cephalad and caudad. The black and dark bluish grey 

 mature coloration is attained fully in not over ten hours. The eyes 

 at moulting, however, are nearly black and very conspicuous by con- 

 trast. 



This little insect is comparatively simple to rear and its 

 smallness makes it an excellent object to examine living under 

 the microscope. Much remains to be found out about it. 

 What is its respiratory system? Where are its spiracles, un- 

 revealed even in the cast skins ? How many eggs does each 

 female lay? Many other questions will occur to the experi- 

 enced biologist, unanswered in what precedes. 



PLATE XXV. 



Life History of Microvelia borealis Rueno. 

 Ova Nymph Third Instar 



Nymph First Instar Fourth 



Second Adult Male 



all X 20. Microphotographs by Mr. Chris. E. Olscn. 



