434 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 2 



of young crawling larvtie from various hosts in different parts of the 

 country to other hosts, and the subsequent changes in size and out- 

 ward appearance, has convinced the writer that the host plant has 

 an unexpectedly potent influence in the development of the insect. 

 During the great outbreak of this scale in Chicago and vicinity in 

 1906, the writer brought from Chicago twigs of maple and box-elder 

 with hundreds of the egg-sacs filled with eggs, and tied the twigs to a 

 number of kinds of trees. In due time the eggs hatched and many 

 of the larva set and molted and developed very satisfactorily on their 

 new food plants, while on some trees a large percentage failed to 

 develop. 



The following spring and early summer brought forth a revelation 

 in the various sizes, colorations and markings of the rapidly develop- 

 ing females on the various food plants. On young rapidly growing 

 sycamore (Platanus occidentalis) and linden (Tilia americana) which 

 were well cared for in large pots, the adult females just before the 

 formation of the ovisac averaged 8 mm. in length and 6 mm. in 

 breadth, and were mottled and marked with unusual brilliancy. The 

 smallest females obtained in this experiment were grown on boxwood 

 (Buxus sempervirens) and averaged but 2.75 mm., while but four 

 specimens reached maturity. Transplantings were successful on 

 apple, pear, quince, mulberry, grape, osage-orange, poison ivy {Rhus 

 toxicondendron) , Ampelopsis tricuspidata, plum, boxwood, spirsea, 

 maple, box-elder, Vihurniim prunifolium, Quercus coccinea, Ptelea 



Explanation of Plate 19 



1. Pseudococcus adoniclum Linn. 



2. Pseudococcus citri Risso. 



3. Toumeyella liriodendri Gmel. 



4. Coccus hesperidum Linn, on Oleander leaf. 



5. Leccmium ccui'ycd Fitch. 



6. Lecanium nigrofasciatuvi Pergande. 



7. Lecanium corni Bouche. 



8. Lecanium persicw (Fab). 



9. Lecanium quercifex Fitch. 



Nos. 5-9 are natural size and photographed simultaneously. 



10. OrtJiezia insignis Dougl. 



11. Asterolecanium variolosuvi (Ratz.) on Oak. 



12. Coccus elongatus (Sign.) on Mimosa. 



13. Neoleca/nium cornuparvum (Thro) on Magnolia twig. 



14. Pulvinaria acericola Walsh & Riley. 



15. Lecanium, corni Bouch^ on Honeysuckle. 



16. Saissetia hemispJicerica (Targ.) on Per sea gratissima. 



