28 



BULLETIN 100, U. S. DEPARTMENT OF AGRICULTURE. 



Table VIII. — Divergences of structure between Monellia corpse Monell and M. caryella 



Fitch. 



Form. 



Monellia caryx Monell. 



Monellia caryella Fitch. 





Antennal joint III very slightly 

 thickened basally. 



Sensoria on antennal joint III 

 occupying basal half or two- 

 thirds. 



Antennal joint VI and its spur or 

 filament subequal, or VI less 

 than spur. 



Dusky knee spots often present. 



Four longitudinal rows of capitate 

 spines. 



Smaller than the viviparous fe- 

 male. 



Four longitudinal rows of capitate 

 spines. 



Antennal joint III quite notice- 

 ably thickened for its basal half. 



Sensoria on antennal joint III oc- 

 cupying basal third. 



Antennal joint VI one-third as 

 long again as its spur or filament. 



Dusky knee spots absent. 



Six longitudinal rows of capitate 

 spines. 



Larger than the viviparous fe- 

 male. 



Six longitudinal rows of capitate 

 spines. 









LIFE HISTORY AND TECHNICAL DESCRIPTIONS. 



Life-history studies on this plant-louse began in August, 1912, at 

 San Jose, CaL, but no rearing work was done until the appearance 

 of the sexed forms in September. Observations taken in August 

 and September indicated a development of the summer generations 

 similar to that found in Monellia caryse. This was further confirmed 

 by studies during 1913. The sexed forms were studied at Walnut 

 Creek and San Jose, Cal. In both localities these did not appear until 

 late in September, even on trees heavily infested. The aphides re- 

 mained on the trees as long as there were leaves on which they could 

 subsist and were to be found until mid-November. After September 

 the great majority of aphides deposited were oviparous, and of these 

 the males were extraordinarily scarce, the writer observing only one 

 individual of this sex among hundreds of oviparous females. Table 

 IX indicates the life cycle of plant-lice deposited by four viviparous 

 females and shows the preponderance of the sexed form over the 

 asexual in the late fall. 



Table IX. — Life-cycle record of the progeny of four viviparous females of Monellia 



caryella, Walnut Creek, Cal., 1912. 



FEMALE NO. 1; DEPOSITED 3 YOUNG. 





Date of— 



Form of individual. 





No. of larva. 



Hatch- 

 ing. 



Molt 1. 



Molt 2. 



Molt 3. 



Molt 4 

 (becom- 

 ing 

 adult). 



Life 

 cycle. 



1 



Oct. 4 

 4 



Oct. 7 



7 



Oct. 10 

 11 



(?) 

 (?) 



Oct. 16 

 18 



Winged viviparous fe- 

 male. 



Oviparous female 



do 



Days. 

 12 



2 



14 



3' 





















FEMALE NO. 2; DEPOSITED 6 YOUNG. 



Oct. 12 



Oct. 15 



Oct. 18 



Oct. 21 



Oct. 



28 



12 



15 



18 



21 





28 



12 



15 



19 



22 





29 



12 



15 



19 



23 





30 



12 



(?) 



(?) 



(?) 





29 



12 



(?) 



(?) 



(?) 





30 



Oviparous female. 



....do 



....do 



....do 



....do 



....do 



Died permaturely. 



