196 TiiH M(»^■'nIl.^ mi.i.KTix. 



;i case wiicrc the iiisi'el has proven to lir of (•coiioiiiic value where iiitro- 

 (iuce(l. and it is now sjciiei-ally aeeepled. hy eiiloniolofjists a1 least, that 

 tlu' ]iarasi1e lias heeii ^iveii a sutlieieiil ti'ial and has been found 1o ])v 

 detioielit. 



The reasons foi' Ihe fadure ol' the insect to eonie up to expectations are 

 probal)ly not far to seek. In the haiulling of the apple crop there are 

 wide tlifferences between the methods in vogue in California and in the 

 native liahitat of ('aUi( pJnalt<s. In California the apples, where grown 

 eonuuereially, are hauled to packing sheds innnediately after p)icking. 

 and placed in bins. This makes it necessary for the codling moth worms 

 to seek winter (juarters within the packing house .structure, where they 

 are practically free from i)arasite attack. In south Europe, liowever, 

 the apples are piled upon the ground, allowing the apple worms to tiud 

 hibernating <piarters in the orchard, thus making many of them avail- 

 able for attack by CaJIicphialtcs. Spraying not being nearly so general 

 in Europe, also gives rise to a large percentage of windfalls caused by 

 the apple worms, and this gives opjiortunity for a still larger supply 

 of the larvfe to find shelter in the orchaid. The ditferences in methods 

 of handling the crop, however, apply principally to the last brood, and 

 the above remarks are a]'»])1ica]ile to a lesser extent to the first brood, 

 which pujiates largtdy in the orchard and should be availalile so far as 

 this factor is concerned for attack by the parasite. It will be seen, 

 therefore, that the apparent failure of ('aUirphiaIt< s is only partially 

 accounted for by the above, and it is necessary to look elsewhere for 

 ex})lanation of its lack of efficiency. This explanation, we believe, is 

 found to lie mainly in the following : 



First — The physical inability of Calli( phiaUcs to oviposit in more 

 than a compai-atively small percentage of the cocoons of the codling 

 moth. This restriction of the aliility of the parasite is a common phe- 

 nomenon and confronts with great frecjuency the student of insect 

 parasitism. It frequently happens that a ])arasite is not fitted l)y nature 

 to accomplish more than a very small aniount towards the control of its 

 host. Probably the most connnon of these restrictions is insufficient 

 length of the ovipositor. This is well illustrated in the case of the egg- 

 l)arasite of the gypsy moth imported into New England from Japan by 

 the United States Bureau of Entomology. Not more than, say 20 per 

 cent, of the eggs of the gypsy moth can by any possibility be parasitized, 

 no matter how abundant the two species of parasites are. The reason 

 for this is that the egg-mass of the moth is composed of several layers. 

 The ovipositors of the parasites are only sufficiently long to enable them 

 to reach the outer layer of eggs. The remaining 80 per cent of the eggs 

 are fully protected, and one might introduce colonies of these parasites 

 until doomsday and not increase the i-ate of parasitism one per cent. 

 Insufficient length of the ovipositor seems rather far fetched when 

 applied to CaUi< phialtrs, which has that portion of its anatomy rather 

 abnormally developed, but nevertheless this fact is undoubtedly respons- 

 ible to a large degree for the failure of ('alli( p}nalf(s to accomplish the 

 control of its host. The specific application in this instance lies in 

 the well-known habit of the apple worm of secreting itself to spin its 

 cocoon. CaUicphialtcs can not. of course, deposit eggs in any coeoon 

 which it can not reach with its ovipositor. Just what percentage of the 

 cocoons are formed out of reach of the parasite has never been deter- 

 mined, but at least a majority of them are so situated. The codling 



