^3U 



THE AGRICULTURAL NEWS. 



October 3, 1908. 



INSECT NOTES. 



Diptera. 



The insocts of thLs order are the two-winged Hies 

 or true Hies. The word ' Hy ' is used in referring to 

 many other insec-ts, especially in combination with 

 some other word which dcisienates the insect according 

 to its habits, its food, etc. Examples of this are to be 

 seen in the terms butterflies, potid Hies, caddis- Hies, har- 

 vest-Hies, all of which belong to different onlers, and not 

 one of them to the Diptera. Another e.xample of this 

 is to be found in the e.xpression ' candle-Hies, ' by 

 which many people in the West Indies designate 

 practically all the small insects that are attracted to 

 the house lights at niglit. Thi.s'terui is used to include 

 small moths (Lepidoptera), beetles (Coleoptera), Hies 

 (Diptera), and (occasionally water-bugs (Hemiptera). 



Tlie fhiiractui's wljirli distiiigui.sli flies frniu ether insects 

 are that the adults never have more tliau one pair nf wings ; 

 a few are wingless. In addition to the wings of the flies there 

 are a pair of halttrex (sometinie.s called balancers), in tlie 

 place u.sually occupied by the liinder pair of wings in other 

 order.s. These are small knobbed organs which are usually 

 plainly to be seen. The wings are membranou.s, usually 

 transparent, and without scales, except in the case of 

 mosipiitos and closely related insects. The mouth parts of 

 the flies are ada])ted for piercing and sucking or for lapping. 

 Many flies are cajiable of inflicting a very painful 'bite,' 

 but none of them are capable of biting in the same way 

 as the beetles or the grasshoppers. 



The larvae of flies are known as maggots. They are 

 usually footless grubs, and they vary greatly in their mode 

 i)f life and in their habitat. Flies jiass through a (■(.nii)lete 

 inetimorphosi.s, including egg, larva, pupa, and imago. The 

 eggs are deposited in a great variety of places according to 

 the habitat of the dirterent specie.s.,and the food of the larvae. 

 In the case of certain species, the young are born alive. This 

 might seem to be a striking exception to the general rule of 

 insect embryology, but it merely mean.s that the eggs are 

 hatched within the body of the female parent fly. 



The order Diptera is one of the most inipniiant of all 

 (ir<lcrs of insects. Not only does it include agricultural })ests 

 i>f the first importance, such as liie Hessian fly, the fruit fly ; 

 and housi'hold pests, such as the liou.se fly, l>ut it also 

 includes tho.sc in.sects which are directly dangerous to iinman 

 life as carriers of iliseasc, .such as mosqnitos, the tse-tse fly, 

 and others. 



The number of species of flies already known to science 

 is about 40,000, and it is estimated that when all I lie exi.st- 

 ing species become known the number will reach a total of 

 :55(),000. In the case of certain .species of this order, the 

 number of individuals in existence at any one time is enor- 

 mous. Especially is this true wherever flies And favourable 

 breeding places and plenty of food for the larvae. Instances 

 in point are the house fly, any species of mosipiito, and the 

 pomace Hies, which are attracted to all kind.s of dei-aying fruit. 



It will be impossible in this brief review to do more than 

 nienti<m a few of tlie important insects of this order wliicli 

 occur in the West Indies. 



Among the Diptera with long antennae the mo.scjnitos 

 (Culicidae) are the most importiuit. These small in.sects are 

 a source of annoyance in nearly all parts of the world, and 

 in all hititudes, by day and night. Many of them also are of 

 great importance on account of transmitting .some of the 

 mo.st deadly diseases of mankind. Yellow fever and malaria. 



which have at times m^lde certain localities alnir.si uninhabit- 

 able, as well as the repulsive filaria, are mosquiio-liorne disea.ses. 



The life-history of mosipiitos in general is as follows : 

 The eggs are laid in water ; the larvae are aquatic, breatli- 

 ing air by means of a re.spiratory tube which is brought to the 

 surfac-e and jilaced iiJ- communication with the air above. 

 The larva feeds on minute organic particles and microscopic 

 animals. On account of tliis feeding habit the larvae of 

 mos(]uitos may be clas.sed as scavengers, agreeing in this 

 respect with many other species of Diptera. The pupa is free 

 moving, but does not' feed, and i.s a true pupa, the change 

 from the larval to the pupal stage being as complete as in the 

 ca.se of the Lepidoptera, in spite of the fact that the insect at 

 this time has a considerable power of movement and locomo- 

 tion. The length of the life cycle in mosquitos varies with the 

 species, and with ci'iiditions of climate, etc. (,'ertain specie.s 

 are able to complete the entire life cycle in a few week,-, while 

 others require much longer. It has been found also that 

 under certain conditions, the length of time required for 

 dHVcdopment is much greater than usual. 



The species of mosquitos found in the West Indies which 

 are of most interest are ty^iiose which carry yellow fever, malaria, 

 and Alalia. The malarial mosquito (Aiinjt/tc/as) does not 

 occur in Barbados, althoygh it is known in all other parts of 

 the American tropics. The yellow fever mosquito (Stct/onii/in) 

 is abundant in the.se islands, being known commonly 

 as the day mosquito or 'Scots grey.' The fliaria-canying 

 nio.s(piitos belong to the genus C'li/e./: The female adult 

 mosipiito.s feed on blood when they have the opportunity ; 

 at other times they probably feed on the .juices of flowers 

 and fruits. The males feed entirely on flowers and fruits, 

 their mouth jiarts not. being ;ula|ite(l toi- piercing, and for 

 sucking blood. , 



The measures to he adopted against mos(juitos fall under 

 .several heads. It is pcs.sible to prevent the development of 

 mosquito.s, within certain limits, by doing away with their 

 breeding places. This is acconqilished by draining swam|w, 

 fliling in ponds, and clearing away all receptacles in wliidi 

 water might collect aujj so furnish suitable places for breed- 

 ing. The A iKijiliflex mysiquito breeds only in fairly permanent, 

 natural |)ools, and in streams. These may be stocked \vith 

 small flsh such as the 'millions' ((Timidiniis /lorri/oiiifx) of 

 I'.ailiados, as has been done at St. Kitt'.s-Xevis, .Xiitigua, and 

 other ]ilaces. These flsh may also be u.sed to stock fountains, 

 tubs, etc., in wiiicli water is kept, and in this way mos(piito.s 

 may be iircvented from breeding in the water, as the flsh are 

 very voracious and feed on the mosi|uito eggs. larvae, and jiupae. 

 It is to the presence aiul abundance of millions in Barbados 

 thai the ab.sence of malaria is attributed. ■ .Millions' inhabit 

 Ihe natural breeding jjlaces of Anojihchs, but other species 

 of mo.squitos naturally breed in places not accessible to the.se 

 small flsh. All cisterns, jwols, etc., that cannot be either 

 stocked with fish or drained, as already suggested, should be 

 treated to application.s of kerosene or petroleum .it inter- 

 vals of a fortnight. 



The use of the mosiputo net at night is strongly to be 

 commeiided. ( 'itronella oil lightly smeared on hands and 

 feet will often keep ott' mosipiitos when no such net i.s 

 available. In case ,of an extreme aluindance of these 

 in.sects, however, the mixture of oil of IVunyroyal 1 part, oil 

 of tar 2 parts, and olive or cotton-.secd oil 2 parts, may be 

 found more efticient than the citronella oil, while in other 

 instances (jf very mild attack, the citronella oil may be u.sed, 

 mi.xed with an equal amount of olive oil. As a relief to thft 

 jiain and irritation often caused by the bite of mosquitos, 

 ammonia applied to the spot has been found useful. 

 {To he (.'out i)i lied.) 



