II 



AGRICULTURAL NEWS. 



March 27, I 



INSECT NOTES. 



A FRUIT FLY ATTACKING PAPAW 



FRUITS. 



The Journal of Ag B for September 21, 



published by the U.S. Department oi Agriculture, 

 contains an article entitled Papaya Fruit Fly. The Papaya 

 oi the Southern United States is the West Indian Papaw 

 (Carica papaya), and as this plant has some importance from 

 ai economic point of view, in certain of these islands, a brief 

 abstract "I the paper mentioned- above, which appears under 

 th< joint authorship of Messrs. Frederick Knab and 

 W. W. Mothers, may be of Interest to readers of the 

 Agricultural News. 



The insect which forms the subject of thi- paper is 

 Torotrypana curvicduda, Gerstaecker. [t was first brought 

 to the notice of the I'.s. Department of Agriculture in 1905, 

 when it was bred from a maggot-infested papaw fruit, from 

 thi Subtropical Plant [ntroduction Field Station at Miami, 

 Florida. Since that time, the increasing importance of the 

 papaw as a possibl i commercial crop has led to investigations 

 i mnexion with this insect. 



The papaw fruit fly is now recorded as occurring in the 

 southern part of Florida, in Costa Rica. Vucatan, Brazil, 

 Peru, Porto Elico, Bahamas, and St. Jean (' St. Jan) Danish 



West Indie-, h i- stated that this last record has 1 a 



erroneously given as St. .Ir.hu, Antigua. 



DESCRIPTION tin LDULT. The papaw fruit tl\ 



(Torotrypana curvicauda) belongs to the dipterous family 

 Trypetidae and exhibits a certain superficial resemblance to 

 a common brown wasp (Polistes). This is due not only to 

 it> similarity of size, form, andgeneral colouration, but in life 

 this is accentuated by the manner in which it walks about oh 

 th< fruit, with its body well elevated upon its slender legs, 

 and by a certain nervousness of movement. The female is 

 remarkable for its long and slender curved ovipositor, which 

 Is thi : ;th of its body. 



[■he ego. The eggs were procured fi gravid females 



by dissection. Thenumbei oi eggs produced bj a single female 

 rs t" be slightly in excess of 100; the counts from two 

 - both showing a distended abdomen and probablj 

 ning a iHM.rU lull complement of eggs, gave 103 



ped i it - No eggs in process of develop 



ent, w Inch indicates thai ill thi eg 

 disposed of within a short period. 



the larva. The larvae are shining, dirty, greenisl 



ii colour while f ling upon the interior seed mass. 



Larvai tha ituretl within the ripened fruit, and that 



■ i into the meat, ire the same rich gol i n 

 ci ilour a I h i ipe fruit. 



i. n - -I i hi larvae. The larvae of the papaw fruit 



flj i thi the fruit, first feeding in the 



central seed mass, bul later, as thej matui and the fruit 



. into the meat and ruining the fruit. The 



number of larvae in a single fruil i ii from two or three 



to tw. at v or '■. Sometimes larvae of different sizes occur 



in th fruit .it the ame time, showing that the 

 infestation was fr more thai i oviposition. 



Cultivated fruil has been found to be generally less 

 ii a i ild, and this i w ibed to the 

 i the flesh "I the cultivated fruits is usually tit 



fleshed varieties appearing to In- more generally 



icked [1 seems that the eggs are deposited inside thi 



cavity, or at least thi insects develop best when this 



Thick-fleshed fruits often showed numerous scars, 



indi iting attemp .it oviposition, when no injurj to the seed 



- or the flesh occurred to indicate the feeding of the 



On the other hand, fruits were noticed, in which 



fully grown larvai were found dead. Thi explained as 



beii I alt oi an attack on fruits which were too 



youi rhe contact with the juice of the unripe fruit is 



quickly fatal to th larvae. It is evident that the fruit 



was too young when attacked, and that the maggots 



mi fully grown and attempted to penetrate into 



the flesh before it was sufficiently ripened, and they were 



killed by contact with the juice, [n the ripe fruit the flesh 



is softer, and the gummy juice is no longer exuded. 



pupal period. The luxe when full-grown usually 



leave the fruit and fall to the ground, when- they pupate, 

 under some bit of ruck or buried in the a depth of one 



or - inches. 



The length of the pupal period is given as seventeen to 

 twenty-one days in Porto Rico, and from thirty to fortj two 

 day- in Florida. The latter figures were obtained as the 

 result of observations in the < 1 season of the year. 



BABITS OF THE ADULT AND OVIPOSITION. The adults of 



this species appear only for a short time just before sunset. 

 A female fly was observed to alight on a well developed but 

 unripe fruit. After walking about a little she insetted the 

 ovipositor its full length into the fruit. As -non as the rind 

 was punctured, the milky juice which the unripe fruit exudes 



whenever injured w -lied forth and began to trickle down over 

 the surface. It is evident that the female th endeavours to 

 thrust her oviposit..] through the flesh to deposit the eggs in 

 the central seed cavity, and that it is only in those varieties 

 with the thinner Meshed fruit that this is successfully 

 accomplished. Tin- larvae are always found in the seed mas-, 

 i scept when the) ere full-grown and the fruit i- ripe, when 



thej penetrate into the flesh with the object of Working 



their way tot] utside in order to get to the ground and 



pupate. 



food plants. Dp to the present time i ther fruit 



than tin- papaw has been recorded a- being eked bj this 



insect, and all attempts to introduce th.- larvae to feed on 



other fruits have, so far, failed. 



RAPID [NCREAS1 OF THE FRUIT FLY. I tilling the last 



two years the papaw fruit fly has rapidly increased in 



abundance, and has extended it- range so as to threaten 



iouslj the future development "t the papaw industry in 

 Florida. This i- largely a result of the increased cultivation 



of the papaw in the southern part of the State. Some 



varieties oi Philippine stock producing large fruits are appar- 

 ently nee from attack. 



CONTROL. I has been pointed OUl that fruit with very 

 thick men escape infestation. While the papaw fruit fly 

 tupts to oviposit on such fruit, the thickness ofthe meat 

 prevent- the tip of the ovipositor from o iching 

 cavity, and in the il i If, tie- Ian le cannot live. It was 



further found that in some fruit- tie larvae had reached 

 maturity I" fore these had ripened, and had been killed by the 



sticl y juice ■ green fruil in endeavoi g to escape. 



Tic means of control that now seem valuable are the 

 production "t varieties "I papaw tin; have thick meat and 



that ripen 3lowly and, the conscientious destruction oi 



adventitious oi wild papaw plants, and of all infested fruits; 



All plant- with inferior fruit should 1.,- eliminated. 



II A. It. 



