NEUROPTERA AND COLEOPTERA 287 



The Pearl-eye {Chrysopa perla) 



In brief papers dealing with Chrysopa perla, Tichomirowa (1890, 1892) 

 states that the eggs of this European insect are found on the leaves of the 

 hnden, maple, wild cherry, and other plants. The incubation period is 

 about nine days. Yolk cells, which are left behind in the outward migra- 

 tion of the cleavage cells, begin active division immediately following the 

 completion of the blastoderm. From the blastoderm the ectoderm and 

 the embiyonic envelopes ^^^ll arise. The yolk cells represent the primary 

 entoderm from a part of which the entoderm is derived. But the greater 

 part is said to develop into mesoderm at the time of the formation of the 

 feebly marked gastral furrow. The germ-band thickening begins to form 

 at the posterior pole even before cell walls appear and is marked by the 

 crowding together of the nuclei in two irregular layers. 



Bock (1939) in an extended account of the development of the same 

 species states that the inner laj^er arises by invagination along the median 

 hne and then spreads out to form the coelomic sacs on each side. A 

 single-layered middle strand lying between the coelomic sacs gives rise 

 to blood cells and the secondary vitellophags. The secondary vitello- 

 phags enter the yolk but Bock was unable to trace their subsequent 

 history. Amnion and serosa arise in the usual way. Cells hberated 

 from the visceral layer of mesoderm wander singly over the yolk surface 

 toward the median ventral line of the germ band to form the anlagen 

 of the mid-gut muscle layers. Later the anlagen of the mid-gut epi- 

 thelium develop into cellular ribbons one on each side closing over the 

 yolk first dorsally and then ventrally. 



COLEOPTERA 



Stylops 



The stylopids, or twisted-winged insects, are small insects that live 

 parasitically within the bodies of bees, wasps, and some Homoptera. 

 Their presence is indicated by the projecting of the body from between 

 two of the abdominal segments of the host insect. The projecting part 

 of the female is the head end, a flat disk-hke plate; that of the male is the 

 rounded and .tuberculate head end of its puparium. The male flies for a 

 brief period; the female remains with only its head end projecting from 

 the host, its body still enclosed in the skin of the last larval instar. A 

 free-flying male fertilizes the female in whose abdominal cavity the eggs 

 are liberated. Here the eggs develop into the triunguHnids, or first 

 instar larvae, which escape from the body of the female through unpaired 

 median genital apertures on the second to fifth abdominal segments. The 

 apertures open into the space between the venter of the female and 

 the puparium which functions as a brood chamber. The triungulinids 



