668 



SCIENCE 



[N. S. Vol. LIV. No. 1409. 



paratus, of tlie host, and so becoming de- 

 posited with the eggs of the latter. 



Fig. 1. Shows relative volume of beetle and 

 parasites. The line XY shows the actual length of 

 the beetle. 



The neveborn larvae measure as follows: 



3.4 (')12, 



28. 



-91. (?)94.8 



2.3 5.2, 



3.7 



2.8 



2.2 0-54. 



Anus none or vestigial; tail conoid, straight, 

 broadly rounded or subtruncate at the term- 

 inus. After deposition along with the beetle 

 eggs, the young nemas moult with little in- 

 crease in size, some of them then boring their 

 way into the body-cavity of even very young 

 larvse of both sexes of the beetle, sometimes 

 to the number of thirty but more often five 

 or six. The following are the dimensions and 

 other details of these young but already sper- 

 matized individuals, as found both in the soil 

 and in very young beetle-larvse, which in the 

 body-cavity of the host reach the above, seven 

 to ten times longer, mature form: 



2. 



16. (?)24. 



•95. (?)97. 



0.5' 



Habitat: Common in the body-cavity (abdo- 

 men, thorax and even head) of Diabrotica 

 vittata, trivittata, and 12-punctata, especially 

 the former, infesting the two sexes about 

 equally. 



My attention was called to this nema by 

 Mr. W. V. Balduf, Assistant Entomologist, 

 Ohio Agricultural Experiment Station, Mari- 

 etta, Ohio, where he discovered the larvEe in 



4.^ 



2.6 



Fig. 2. Cucumber-beetle egg and the charge of 

 nemas deposited with it. 



the course of experiments on Diabrotica. 

 Owing to the economic aspect of the subject, 

 beetles sent me by Mr. Balduf were exhibited, 

 dissected, at the Washington Helmintholog- 

 ical Society's meeting, March 17, 1921. Ex- 

 amination revealed the adult female form, 

 which is so flaccid and otherwise deceptive 

 as to cause it rather easily to be confused 

 with the internal organs of the host by one 

 not versed in both insect and nema anatomy. 

 Aided by Dr. F. H. Chittenden and col- 

 leagues of the Federal Bureau of Entomology, 

 and by others, the geographical distribution 

 of the nema was studied with results shown 

 on the accompanying map, which indicates 

 that the distribution in 1921 is probably 

 nearly coextensive with that of the main hosts, 

 Diahrotica vittata Fab. and trivittata Mann. 

 The nematism is often high and affects on the 

 average about 20 per cent. (0 per cent. — 70 

 per cent.) of the insects. Beetles from a 

 locality where they are not nematized are 

 larger and more vigorous. Thus twenty-five 



