26 



THE AGRICOTLfURAL NEWS. 



Januaey 21, 1911. 



INSECT NOTES. 



Fk;. 2 



AN INSECT PEST OP CACAO IN UGANDA. 



In a previous number of tlie Aijricultural Xewf (Vol. 

 IX, p. 42), certain insect pests known in Uganda were men- 

 tioned. The following notes on tlie cacao fruit fly are 

 prepared from an -iccount recently received from Mr. C. 0. 

 Gowdey, Entomologist to the Government of Uganda. 



It may be mentioned that fruit flies occur ia the West 

 Indies, but are not often sufficiently abundant to cause much 

 damage. Up to the present time, however, cacao has not 

 been known to be attacked by these insects, and it may be 

 of interest to record the fact that such attacks are known 

 elsewhere. 



The fruit flies belong to the order 

 Diptera, and the family Trypetidae. The 

 Mediterranean fruit fly (Ceratitis capitata) 

 — a most important pest in many parts of the 

 the world — and the Mexican orange worm 

 {Try/ieta liulens) are near relations of the 

 cacao fruit tiy of Uganda (Ceratitis 2}u>ictatn]. 

 The Mediterranean fruit fly and the Mexican ^ 

 orange worm were discussed, and figures were 

 given in the Ai/ricultural Newi^, Vol. VII, 

 p. 410. 



The accompanying figures are reproduced 

 here in order to convey to readers of the 

 Ayricultiiral JVeirs an idea of the general 

 appearance of insects of this kind. ^ 



DESCRIPTION -\ND LIFE-IUSTORV. The 



cacao fruit fly attacks the ripening pods of 

 cacao, the eggs l)eing laid under the peel of 

 the pod in a puncture made by the short 

 ovipositor. 



The eggs are colourless, and so very minute that it is 

 possible to find them only when the actual deposition has 

 been ob.served. The young larvae emerge from the eggs in 

 from twelve to fifteen days, and immediately begin tunnell- 

 ing into the pod, and feed on the pulp surrounding the 

 seeds, preventing the normal development of the.se. The 

 maggots, as the larvae of Diptera 

 are generally called, are footless, 

 colourless, twelve segmented grubs 

 with prominent, dark-coloured man- 

 dibles. They are very active, leap- 

 ing great distances. When fully 

 grown, they measure about i-inch 

 in length. Full growth is attained 

 in from fifty-five to sixty days; in 

 an exceptional case it required only 

 forty-five days. The maggot now 

 untlergoes a metamorphosis, result- 

 ing in the formatinii of a puparium. 

 This metamorpliosis takes place 

 in the soil at a depth of about 

 2 inches, at the base of the trees. 

 The puparium varies in colour from 

 •white to pale brown; it is barrel- 

 shaped, and the segmentation is still apiiarent. The 

 puparial stage, which is the inactive period, lasts from 

 fifteen to seventeen days. From the puparia, the adults 

 emerge and the life-cycle begins again. The ground colour 

 of the adult is yellowish-white; eyes red, i)ur|ili.sli in .some 

 lights; thorax lieautifnlly striped and spotted: abdomen, 

 except basal segment, spotted and with black bristles at 

 apex; wings with fuscous bands and dark siiots. Tiie 



Fig. 3, Mexic.vn Okanci; 

 {7'ri/pet<i ludi'its.) 

 Adult female. 



life-cycle requires from seventy-seven t(i ninety-two days for 

 completion. The adults feed on any sweet substance which 

 may be available. 



NUMBER OF GENERATIONS, There is no sharply defined 

 season between the broods; their appearance is continuous. 

 Breeding is carried on witliout interruption as long as food is 

 available, since in Uganda there is not a range of tempera- 

 ture sufticiently great to make a period of hibernation 

 imperative. 



FOOD I'LKNTs, The eggs are deposited in several varie- 

 tie-5 of fruit, including the mango, guava, melons, and 

 passion-fruit. There is usually, therefore, some kind of 

 fruit availalile for the insect throughout the year, allowing 

 an uninterrupted succession of broods. Instances are on 

 record, however, in which the succession of fruit was broken 

 and yet the appearance of the fly was 

 continuous. This fact may be accounted 

 for either by assuming that the insects 

 have unknown wild food plants, or that 

 any one or all of the stages can exist 

 longer without food than is at present 

 known. In either case, the circumstan- 

 ces are beyond control, and necessitate 

 a means of destruction of the flies as 

 soon as they appear on cultivated fruits. 

 1,'ONTEOL MEA.suRES. The fact that 

 the adult fly feeds on sweet substances 

 makes possible the u.se of a poison bait 

 as a means of control. The most satis- 

 factory poison bait is prepared by using 

 the following: — 



Sugar 3 lb. 



Arsenate of lead ]-Ib. 



Water .5 gallons. 



This mixture may be applied by means 

 of a syringe or sprayer, and should be kept thoroughly 

 stirred, to prevent the arsenate of lead from settling. 

 A thin film of this solution of poison and sweetness, spread 

 over the leaves of the plant when the adult flies are abund- 

 ant, has been found very useful. 



Burning and burying the infested pods are also recom- 

 mended. If the latter course is 

 adopted, the pods should be covered 

 ly at least 2 feet of earth. 



It does not seem that the 

 Uganda cacao fruit fly is at all 

 likely to be introduced into the West 

 Indies, but it would be well for cacao 

 planters and others to realize the 

 l)ossibility of such an introduction; 

 while the recognition that a pest of 

 the character of the one under dis- 

 cussion is known to attack cacao 

 should make it possible to recognize 

 and to check similar attacks, if they 

 should be experienced. 



Mexican Grance Worm 

 {Trypeta Indent.) 

 ii, larva, c, puparium. 



Worm. 



An interesting illustration of the 

 increasing impurtance that is being attached ti) the control 

 of insects by parasitic forms of them is given in the Biitomo- 

 /o;/ /(•(((' A*«w.« for January 1911 (Vol. XXII, No. 1). It is 

 stated there that two investigators attached to the Bureau 

 of Entomology of the United States Department of Agri- 

 culture are being sent to Panama, during this month, for the 

 pur|)Ose of searching for parasites of the citrus white fly {Aley- 

 rodfjs citri), and of the cotton boll weevil and allied species. 



