1974] 
Cooper — Boreus 
I 03 
By the next day (day 16) the larvae moved occasionally within the 
chorions. By day 18 the larval gut appeared swollen and gray. Over 
the next five days the larvae became very active, even reversing their 
positions within the eggs; at times the chorion of an egg would col- 
lapse inwards, only to reinflate once again. On the 24th day two of 
the larvae hatched by means of great rents torn through the chorion 
(fig. 3C). I did not observe the emergence, or how the chorion was 
torn open. As there is no egg burster such as Gassner (1963) has 
described for the first instar larva of Panorpa nuptialis Gerst., it is 
possible that infolding of the chorion, as earlier observed, enables the 
larva to seize and rip the chorion with its jaws, or that the gray band 
on the chorion is associated with a local weakness. Striibing (1950) 
has described the swelling of the developing egg (which also occurs 
in other Mecoptera, see Currie 1932, Setty 1940, Byers 1963), and 
the hatching of B. hyemalis which takes but 10-12 minutes; the 
events prior to hatching are similar to those of B. notoperates} 1 
The newly hatched larva of B. notoperates (fig. 3D) is dead 
white, except for the pale amber head capsule, darker jaws, and pig- 
"Some 127 developing eggs of B. notoperates were at hand when this 
passage was written (Feb. 1974). Subsequently they were divided into two 
lots of which one (of 88 eggs) was followed daily to hatching. All had 
been kept at 9°C, and were at a mean age of approximately 30 days when 
removed to 20°C for observation. They had all undergone swelling, but no 
other sign of development was discernible. The smallest egg was 0.58 X 
0.44 mm, the largest 0.78 X 0.52 mm, and the most distended in girth was 
0.64 X 0.56 mm. In what follows, day 0 is the day of removal (Jan. 14, 
1974) to 20°C. 
At day +15 eyes were visible in nearly all eggs; at +21 heads pale 
testaceous, eyes black, mandibles very dark and active ; most eggs alike in 
stage — despite this, hatching spread out over a period of 36 days. 
Hatch was 93% (82 of 88 eggs; 2 did not mature, 3 failed to hatch but 
had had active larvae, 1 killed by mold). First egg to hatch was at +25 
days, half of the eggs had hatched at +31, three-quarters at +33, 90% by 
+ 38, and the last on +61. 
Unlike the mandible of the last larval instar, that of the unhatched larva 
has a sharp, falcate, apical tooth, a moderately long, sharp, subapical tooth, 
and two successively smaller, sharp denticles. When hatching commences, 
the turgid chorion is abraded, then penetrated, by the mandibles, whereupon 
it collapses somewhat and folds inward to a varying degree, owing to loss 
of fluid from the egg. Within an hour, or as long thereafter as several 
days, the larva emerges. It does so by cutting through the fold, and else- 
where, to produce a broad apical flap, or even a free cap to the egg. By 
peristaltic movements, especially of the thorax, the larva forces the flap 
and emerges through the gaping hole in the chorion in a matter of ten to 
twenty minutes. 
