CBOSSING EUSCHISTUS VARIOLARIUS AND EUSCHISTUS SERVUS. 371 



References. 

 Castle, W. E. 



1911. " Heredity in Relation to Evolution and Animal Breeding." 

 D. Appleton & Company. 



1912. "The Inconstancy of Unit-characters." Amer. Nat., vol. xlvi. 

 Foot, K., & E. C. Strobell. 



1913. "Preliminary Note on the Results of Crossing two Hemipterous 

 Species with Reference to the Inheritance of an Exclusively Male 

 Character, and its Bearing on Modern Chromosome Theories.^' 

 Biol. Bull.j vol. xxiv. No. 3. 



PUNNETT, R. C. 



1911. " Mendelism." The Macmillan Company. 



EXPLANATION OF THE PLATES. 



All the photographs are of male specimens. In all cases only the ventral surface 

 of the bugs is shown. 



The two bugs of photo 1 are dried specimens. Those of photos 2 to 06 are preserved in 

 glycerine *. The specimens are placed serially in a small test-tube which is tilled with pure 

 glycerine and hermetically sealed. The genital segment of each bug has been pulled out 

 and cotton inserted behind the segment to hold it in position to show the entire ventral 

 surface. 



The magnification is about 1| diameters : this varies slightly because the work was done 

 by two photographers, and they did not give exactly the same enlargement. The repro- 

 ductions are bromide prints made directly from large negatives of the original plates ; the 

 individual photographs of which these plates were composed being sunprints from the 

 eriginal negatives. 



PliATE 28. 



Photo 1. Male specimens of Euscliistus variolarius and Euschistus servus. On the left is 

 E. variolarius, showing the ventral surface and the clearly defined black 

 spot, always present on the genital segment of the males of this species. 

 On the right is E. servus, showing the ventral surface and the genital segment 

 without any trace of the black spot typical of variolarius. 



Photo 2. Seven male specimens of E. variolarius, showing the typical black spot on the 

 genital segment. These specimens are from the first generation of 1912. The 

 parent bugs were of the first generation of 1911, which were kept in captivity 

 through the winter of 1911-12. 



Photo 3. Five male specimens of E. servus received from North Carolina in the fall 

 of 1912. 



Photo 4. The wild E. servus male that fertilized the E. variolarius female. 



Photo 5. Three of the five E. servus males that were caged all winter with E. variolarius 

 females : see page 342. 



* We are indebted to Prof. Ealph Tower, of the Museum of Natural History of New 

 York, for suggesting the use of glycerine as a preservative. 



LINN. JOURN. — ZOOLOGY, VOL. XXXII. 31 



