440 AN INTRODUCTION TO ENTOMOLOGY 



narrow. The puparium is box-like, the body of the insect being 

 elevated on a palisade of vertical wax rods (Fig. 511, d). There are 

 other rods of wax represented in the dorsal view of the puparium 

 (Fig. 511, c)- 



The most successful means of destroying this pest is by fumigation 

 of infested greenhouses with hydrocyanic acid gas. 



The strawberr^^ white fly, Asterochiton packardi. — This species is 

 closely allied to the greenhouse white fly, but differs in minute char- 

 acters presented by the spines and wax rods of the immature forms. 

 It infests strawberry plants, and is a hardy species, passing the 

 winter in the e^^ state out of doors. 



The citrus white fly, Dialeurodes cUri. — This is a well-known pest 

 in the orange-growing sections of our countr>% and is also found in 

 greenhouses in the North. It infests all citrus fruits grown in this 

 country and is found on several other plants. 



This insect injures its host in two wa^^s: first directly, by sucking 

 the sap from the leaves ; and second indirectly, by furnishing nourish- 

 ment, in the form of honeydew.to a fungus, the sooty mold (Meliola 

 camellice), which forms a dark -brown or black membranous coating 

 on the leaves and fruit, and thus interfering with the functioning of 

 the leaves, retarding the ripening of the fruit, and decreasing the 

 yield of the fruit. There are from two to six generations of this 

 species in a year. An extended account of it is given by Morrill and 

 Back ('11). 



The maple white fly, Aleurochiton forbesii. — Figure 509 represents 

 this species, which is fairly common on maple, but rarely in sufficient 

 nimibers to do serious injury. 



Family COCCID.E 

 The Scale-Insects or Bark-Lice, Mealy-Bugs, and others 



The family Coccidse includes the scale-insects or bark-lice, the 

 mealy-bugs, and certain other insects for which there are no popular 

 names. To this family belong many of the most serious pests of 

 horticulturists ; scarcely any kind of fruit is free from their attacks ; 

 and certain species of scale-insects and of mealy-bugs are constant 

 pests in greenhouses. Most of the species live on the leaves and 

 stems of plants; but some species infest the roots of the host-plants. 

 The great majority of the species remain fixed upon their host during 

 a part of their life-cycle, and can thus be transported long distances 

 while yet alive, on fruit or on nursery stock ; this has resulted in many 

 species becoming world-wide in distribution. Most of the species are 

 minute or of moderate size ; but some members of the family found in 

 Australia measure 25 mm. or more in length. 



While the economic importance of this family is due chiefly to 

 the noxious species that belong to it, it contains several useful species. 

 The most important useful species at this time is the lac-insect, 

 Tachdrdia Idcca. The stick-lac of commerce, from which shell-lac 



