102 APPLE. FRUIT — APPtE THRIPS. 



and horny, with numerous impressed transverse lines, and changes 

 to a dull yellow or a black color, and those speeies which have 

 two, horns forward of the tip still retain them. Within this shell 

 the insect puts on its pupa form, from which the fly subsequently 

 hatches. 



The aphis likewise has foes within as well as without. In ad- 

 dition to the several insects of which we have now treated, all of 

 which attack it externally, it has internal enemies also, a group 

 of insects which dwell in the interior of its body during their 

 larva state, and eventually kill it. These are nearly as efficient 

 in keeping its numbers reduced as any of those which we have 

 been considering. We will speak more particularly of them in 

 eonnection with the aphis which infests the cherry. 



A succession of the several species of these different kinds of 

 destroyers are making their appearance the whole season through, 

 and as many of these species are among our most common insects, 

 it will at once be perceived that they render us most important 

 services in destroying these pests of vegetation, and preventing 

 them from becoming excessively multiplied notwithstanding their 

 unparalleled fecundity. Bat without actually observing them at 

 their accustomed work no one can fully appreciate their value to 

 us, and the amount of herbage which they save from destruction. 

 Wherever plant-lice become numerous there these several kinds 

 of enemies speedily congregate and rapidly multiply, devouring 

 ilicredible numbers of these vermin, and often in a surprisingly 

 short space of time completely exterminating them. 



AFFECTING THE FRUIT. 

 In a round cavity ate near the tip end of tlie young fruit; a minute, very slender 

 blackish-purple insect, with narrow silvery-white wings upon its back 

 resembling a long T-shaped mark. 



The Apple Theips. Phlaothrips Mali. 



Although a profusion of flowers in the spring is often hailed as 

 a harbinger ofa copious yield of fruit, this expectation is very 

 ffequeiitly disappointed. Whilst they are yet young, quantities of 



