MICROORGANISMS IN THE EGG 143 



As has been stated above, the germ, or sex cells in Hylohius, Sibinia, 

 and Calandra become infected with symbionts (bacteria) at the time of 

 blastoderm formation. This applies to all sex cells, both male and 

 female. The symbionts degenerate in the immature testes. In the 

 ovaries the larger mass of microorganisms become lodged in the proximal 

 lying nurse cells of the ovarian tube, although there are symbionts in the 

 oocytes as well. The early infection of the primordial germ cells seems to 

 be typical for all snout beetles except the Cleoninae. 



In many Apionidae the mycetom is represented by a clavate tubule 

 adjacent to the four Malpighian tubes. In Protapioji two of the six 



siom 



L.)r{ /Vf -Lyf-p Ci,_) 



Fig. 58. — Hylobius abietis. Passage of the mycetom {myct) between entoderm (ent) 

 and ectoderm (eci) nearly completed forming a ring around apex of stomodaeum (stom). 

 {From Scheinert.) 



^Malpighian tubes become infected. Ceutorhynchus and Cionus possess 

 infected cells which are derived from infected embryonic tissue and later 

 in part unite to form an organ-like structure. In a species of Lixus the 

 larva emerging from the egg feeds upon the infected eggshell and thereby 

 becomes infected. 



Other Orders. — References to the symbionts occurring in the embryos 

 of other insects will be found in Part II under Mallophaga and Anoplura. 



References 



Blochmann (1888, 1892), Brues and Glaser (1921), Buchner (1930), Emeis (1915), 

 Fraenkel (1921), Glaser (1920), Glasgow (1914), Hecht (1924), Heymons (1895a), 

 Hinman (1932), Hirschler (1912), Hovasse (1930), Klevenhusen (1927), Koch 

 (1931), Mansour (1927, 1930, 19346), Mercier (1906), Pierantoni (1927), Richter (1928), 

 Ries (1931), Scheinert (1933), Scholzel (1937), Schrader (1923), Shinji (1919), Speyer 

 (1929), Sulc (1910), Tarsia (1933), Tiegs and Murray (1938), Toth (1933), Uichanco 

 (1924), Walczuch (1932). 



Buchner's text has an extensive bibliography. 



