DIPTERA 153 



Platy-psyl'la casto'ris is the sole representative of the family Platypsyl'lidce. 

 This queerly shaped beetle lives a parasitic life upon beavers. It is wingless 

 and blind, and the elytra arc rudimentary and short, exposing five abdomi- 

 nal segments. Its degeneration is due to its parasitic life. 



The lady-bugs {Coccin<i'liil(v) are interesting little predaceous beetles, 

 yellow or reddish, with black spots. The cottony cushion-scale {Ice'rya 

 purchasi), so destructive to California fruits, was subdued by a lady-bug 

 {Veda'lia cardind'lis) brought from Australia to feed upon it. The hop 

 louse is destroyed by the larvae of certain lady-bugs known as " niggers." 

 The lady-bugs, with few exceptions, are predaceous. One {Epilach'na 

 horea'lis) is herbivorous. Its larva, which is yellow and clothed with 

 forked spines, feeds upon the leaves of the squash family. 



The little carpet beetle {Anthrc'nus scrophida'rice) is a household pest. 

 Its larva feeds upon carpets, furs, feathers, and woolens. 



The fireflies {Lampyr'idoe) or " lightning-bugs " are not flies, but beetles. 

 The light giving has never been fully explained. " The light-giving organ 

 is usually situated just inside of the ventral wall of the last segments of the 

 abdomen, and consists of a special mass of adipose tissue richly supplied 

 with air-tubes (tracheie) and nerves. From a stimulus conveyed by these 

 special nerves oxygen, brought by the network of tracheae, is released, to 

 unite with some substance of the adipose tissue, a slow combustion thus 

 taking place. To this the light is due, and the relation of the intensity or 

 the amount of light 1o the amount of matter used up to produce it is the 

 most nearly ix'rfcct known to physicists. "^ 



Myrmecoph'ilous Beetles. — There are nearly one thousand species 

 of beetles which live in the nests of ants. Many of them are commensal 

 with the ants, deriving perhaps the greater benefit by the association, but 

 others live truly symbiotically with their hosts.^ They secrete a sweet 

 substance which is eaten by the ants, which in return shelter, clean, and, 

 by regurgitation, feed them. They are strangely modified for this mode 

 of life, usually by degeneration. 



ORDER IX. DIP'tERA 



This order contains al)out fifty thousand species, of which 

 about seven thousand are known in America. It includes some 

 famous flies (Fig. 124). 



The mouth 'parts are adapted for piercing and sucking or for 

 lapping. Just what constitutes these mouth parts is a contro- 

 verted question among scientists. Comstock says, ''According 

 to the most generally accepted view the six bristles represent 

 the upper lip (lahrum), the tongue {hijpopharynx) , the two 

 mandibles, and the two maxillae, and the sheath enclosing these 

 bristles is the lower lip (labium)." Identify these parts on the 

 head of a big fly with the aid of a large figure and a magnifying 

 glass. 



1 Kellogg, p. 269. 2 Kellogg, p. 553. 



