Heterotylenchus aberrans Bovien, 1937, is a body eavity 

 parasite of the onion fly, Hylemya antiqiia (Moig.), and its 

 life history was studied by Bovien (1937) at Lyngby, Den- 

 mark. Tlie onion fly hibernates in the pupal stage and emerges 

 in May to lay eggs on onion plants or in nearby cracks in the 

 soil. The young fly larvae move down the plant usually inside 

 the sheath and finally burrow into the bulb. Pupation takes 

 place in the soil or occasionally in the bulb. There are two or 

 perhaps, occasionally, three broods a year with considerable 

 overlapping. 



In the body cavity of infected flies one finds from one to 

 four large, adult females of B. aberrans (Fig. 172 N) and a 

 greater number of smaller, adult females (Fig. 172 O). The 

 larger individuals are females of the gamogenetic generation 

 and the smaller ones are females of the parthenogenetic gener- 

 ation. The reproductive organs of a gamogenetic female, as 

 compared with these structures in most allantoneraatids, are 



exceptionally small. Much of the space within the body is 

 occupied by the intestine which, according to Bovien, is with- 

 out a lumen. A small stylet is present and the three esophageal 

 glands, empty and reduced in size, are grouped around the base 

 of the esophagus. Eggs (Fig. 172 J) are deposited in the body 

 cavity of the host where they hatch and whore the larvae de- 

 velop into parthenogenetic females. 



The outstretched reproductive organs of a parthenogenetic 

 female are relatively much larger than those of a gamogenetic 

 female. The esophagus and esophageal glands have almost com- 

 pletely degenerated but a small stylet is present and, according 

 to Bovien, the intestine is represented by a single row of 

 large, binuclear cells. Eggs (Fig. 172 K), which are smaller 

 than those of the preceding generation, are deposited in the 

 body cavity of the host and from them develop larvae of both 

 sexes. These larvae remain in the host until they are ready to 

 undergo their final molt when they penetrate the fly's ovaries. 



Fig. 177. SPH.VEKULARIINAE 



. A-D — Sphaerularia bombi (A — Fully grown lavva; B-D — Adult para- 

 sitic females showing progressive stages in prolapsus of uterus. For 



fully grown adult parasitic female, see Fig. 115 A, p. 136). E-I 



Tripius gibbosus (E — Newly born larva; F — Young but sexually mature 

 fomale; Ci — Sexually mature male; H — Adult parasitic female' showing 



early stage in prolapsus of uterus; I — Adult parasitic female showing 

 late stage in prolapsus of uterus. For stage intermediate between H 

 and I. see Fig. 115 K, p. 136). J — "Ti/lerwlius sulphureus piceae." 

 adult parasitic female. A-I. after Leuckart. 1887; J, after Fuchs. 1929 



262 



