522 



TEXT-BOOK OF ENTOMOLOGY 



When the eggs are deposited in exposed places, and remain in 

 such situations for several days, or weeks, or even through the 



FIG. 497. Egg with embryo of honey-bei-. x4i>: //. chorion ; (/it, ganglia; s. ga, brain; jm, 

 jaw-muscles forming; c, cesophageal collar; fb, fore intestine : mb, mid-intestine; at>, hind-intes- 

 tine. After Cheshire. 



winter, the shell is either solid and strengthened by the ribs and 

 ridges; or the shell, if of winter eggs, is unornamented, and is dense 

 and solid, to resist extremes in temperature or the attacks of egg- 

 eating birds, mites, etc. 



The micropyle. This is an opening or 

 canal, or, as in most insects, a group of 

 canals situated at the anterior end of 

 the egg for the entrance of the sper- 

 matozoa during the process of fertiliza- 

 tion of the ovum (Fig. 498 ). In Acry- 

 dians, however, the micropyle is situated 

 at the posterior end of the egg. The 

 micropyle (Fig. 499) is a complicated 

 apparatus within whose circumference 

 the vitelline membrane appears to be 

 firmly attached to the chorion, so that 

 the perforation passes through the cho- 

 rion as well as the yolk-membrane. 



The micropyles of the cockroach are 

 probably as simple and generalized as 

 in any insect. Wheeler states that they 

 are in Phyllodromia scattered over the 

 end of the egg, " over a quadrant of the 

 upper hemisphere, where the beautiful 

 hexagonal pattern of the chorion gives 

 away to an even trabeculation." The 

 micropyles are wide-mouthed, very 

 oblique, funnel-shaped canals, perforat- 

 ing the chorion, the apertures of the fun- 

 nels appearing under a low power as 



Fro. 498. Micropyle (JUk) of i-i^s : 

 ii. of 11 rty, Antomyia"; b, DrotOpKila 

 i'ill<i, -ix; <. stalkt-d i-srir of I'<ti<i*<-nx 

 I, t/tacent. After Leuckart, from Per- 

 rier. 



