VIABILITY AND FECUNDITY OF ALATE ALIENICOLAE OF APHIS FABAE SCOP. AFTER FLIGHTS TO EXHAUSTION BY A. J. COCKBAIN

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1 I '. Exp. Biol. (1961), 3, 'ith 2 text-figures Printed in Gret Britin ll VIABILITY AND FECUNDITY OF ALATE ALIENICOLAE OF APHIS FABAE SCOP. AFTER FLIGHTS TO EXHAUSTION BY A. J. COCKBAIN Rothmsted Experimentl Sttion, Hrpenden, Herts {Received 12 August i960) INTRODUCTION I hve studied the effects of exhustive flight on Aphis fe Scop, to see if long migrtory flight is likely to ffect the susequent life nd reproductive potentil of phids. MATERIALS AND METHODS Alte lienicole of pproximtely uniform size were otined from helthy colonies of the sme clone mintined in the lortory t 1 ±5 C. on rod ens (Vici f L., vr. Cludi Aqudulce). They were collected within \ hr. of the finl ecdysis nd kept for 24 hr. on young ens in the drk t 20 C. to complete their tenerl development nd ecome redy for flight (Tylor, 1957). The phids were flown on pins (Cockin, 1961) t C, 21-4% R - H -> n(^ in n ir strem of 1 m.p.h. Experiments 1-5. Within ech experiment there were two experimentl ( nd ) nd two control (c nd d) tches, 7- phids per tch. Test phids were flown to exhustion nd control phids were flown for 15 min. in order to induce settling (see B. Johnson, 195; Kennedy, 195). After flight the phids were kept in drkness on young ens, one tch per plnt, t 20 0 C. nd 45 % R.H., nd rought into light t the sme temperture nd humidity fter 3 dys, i.e. when they hd lost the ility toflyecuse their flight muscles hd utolysed (B. Johnson, 1957). Lrve produced y the phids were counted nd removed when the plnts were chnged every 2-3 dys, or whenever n dult died. Experiments 6-. Test phids were flown to exhustion nd then strved in glss tues in drkness t 20 0 C. nd 70 % R.H. ; unflown controls were strved under the sme conditions. RESULTS Flight durtions nd susequent ehviour Behviour during prolonged tethered flight nd determintion of the point of exhustion hve een descried elsewhere (Cockin, 1961). Most phids flew continuously for long periods, requiring only occsionl stimultion, until they ecme ftigued. Further flight my hve een possile fter period of rest s in Drosophil (Wigglesworth, 1949), ut it is doutful whether the durtion of flight could hve een incresed significntly. Flight durtions in different experiments were consistent enough to give confidence in the method. Tle 1 gives men, minimum nd mximum durtions. Flights of 3-9 hr. re

2 12 A. J. COCKBAIN typicl of tethered culture phids in the tempertures nd humidities stted ove; vritions re prtly ecuse the mounts of flight reserves differ (Cockin, 1961). Expt. ws t very low humidity (men sturted deficit 23 mm. Hg), ut the men flight durtion did not differ significntly from tht of the other experiments; wter loss y evportion, relted to the humidity of the ir, is evidently not limiting fctor to flight under these conditions. Tle 1. Flight durtions t C. of the i-dy-old phidsflownto exhustion Expt. no. H.H. (%) Btch no. No. of phids... Flight durtion (hr.) /Men {Min. I Mx. i *. 7 ± \ ' A ( N 67±3 S r 7 S ^ ±4 S-i 7'5 4'5 6 '3 6-i ±4 14 5'5 2-S o 7 79± i ±3 IO The exhusted phids in Expts. 1-5 settled nd egn to feed within few minutes of eing plced on the plnts. A few of the controls ttempted to tke-off fter proing, ut flight ws prevented y plcing the insects in drkness. None of the exhusted phids ws distured when exposed to light for min. on the following dy, ut some controls immeditely egn to wnder nd flight hd to e prevented gin y drkness. An ttempt ws mde to fly the exhusted phids of two experiments (4-5) on the second dy. Some would not fly nd the others were difficult to strt. Those which filed to fly could rise their wings ut ppered unle to et them; this is sign of the eginning of flight-muscle utolysis nd further flight my hve een impossile. Tle 2 shows men, minimum nd mximum durtions of second flights, nd the percentge of phids which filed to fly. The corresponding controls, tches 4 c nd 4^, 5 c nd ^d, were flown with no difficulty for further 15 min. Tle 2. Flight durtions on the second dy of phids previously flown to exhustion Expt. no. 4 5 Btch no. % unle to fly [Men Flight durtion (hr.) Min. (Mx i i i-o 'O o Of the exhusted phids in Expts. 6- (strved fter flight) twenty-eight per cent were le to tke-off nd fly when exposed to direct sunlight on the following dy. Most of them flew upwrds towrds the light, s is chrcteristic of first flight. The remining exhusted phids could not tke-off, some eing moriund or ded. Of the unflown controls eighty-eight per cent were le to tke-off nd fly on the second dy.

3 Viility nd fecundity of lte lienicole of Aphis fe 13 Longevity fter flight Tethered flight to exhustion did not ffect the longevity of phids llowed to settle nd feed on host plnt fter flight (Expts. 1-5). The men dult life of ech tch rnged from 24 to 36 dys for exhusted phids nd 2-37 dys for controls (Tle 3). A mximum life of 41 dys for individul phids occurred with oth exhusted nd control insects. Within the sme experiment, one control tch (3 d) lived significntly longer thn n exhusted tch (36) (t = 2-37; P = ), nd one exhusted tch (5 ) lived significntly longer thn control (5^) (t = 2-39; P = o-o5-o-o2). Men dult lives of 31T nd 32-4 dys for comined dt for exhusted nd control phids respectively showed no significnt difference (t = i'o3; P > o-io). Tle 3. Men dult longevities of phids feeding on young en plnts (Expts. 1-5) Exhusted phids Control phids Btch no. 1(2 16 z 2 3" 3 4<2 4* 5<* S Men Men longevity (dys) 2-5* o»* S+t (±) "S u- II-O 2-2 i Btch no. IC id 2C zd 3C 3d AC 4d 5C 5<* Men Men longevity (dys) 34-6* i "3t 34-o»* (±) i-5 S-4 3-i H i o *, ** Differences significnt t 10% level; f> t t differences significnt t 5 % level. Fig. 1 shows survivl curves for exhusted nd control phids in Expts The curves devite slightly when ll phids re considered (1 A) ut re lmost identicl when the comprison is restricted to phids of uniform size, i.e. hind tii length mm. (0 % of the exhusted nd 75 % of the control phids in Expts. 1-5) (Fig. ib). Aphids strved fter flight exhustion lived for significntly shorter time thn phids strved without flight (Tle 4). Men survivl time of flown phids in Expts. 6- ws 30-3 hr., i.e. they lived for c hr. fter flight; men survivl time of unflown phids ws 55-2 hr.; these mens were significntly different (t = 7-6; P < o-ooi). The unflown controls in Expt. 6 lived significntly longer thn those in Expts. 7 nd (t = 3-4 nd 3-54 respectively; P = O-OI-O-OOI); this ws ssocited with their greter size, s indicted y hind tii length. There ws positive correltion etween survivl time nd hind tii length in the control phids (r = ; P = ), such tht difference of o-i mm. tii length ws ssocited with difference of 13 hr. in length of life during strvtion; no correltion ws found

4 14 A. J. COCKBAIN etween survivl time nd hind tii length in the exhusted phids (r = o-c-6; P > o-io), nor etween length of life fter flight nd flight durtion in these phids (r = 0-119; P > o-io) "15 6 o Fig. 1. Men percentge survivl of phids feeding on young en plnts (Expts. 1-5). A, ll phids; B, phids with hind tii length mm.; O, exhusted phids;, control phids. Reproduction fter flight Flight to exhustion hd no effect on rte of lrviposition or on totl numer of lrve deposited y phids llowed to feed fter flight. The men ccumultive totls of lrve orn to exhusted nd control phids in Expts. 1-5 were similr (Fig. 2 A, B). The highest rte of lrviposition ws during the 24 hr. following flight in oth exhusted nd control phids, with mens of 11*4 nd n-o lrve/phid respectively. The rte then decresed to men of 2 lrve/phid/dy fter 4 dys nd incresed to 6 lrve/phid/ dy fter out dys. A decrese occurred towrds the end of the reproductive period which vried from to 29 nd to 30 dys in the exhusted nd control tches respectively. The reproductive cpcities of phids which completed their reproductive life were out the sme in ll tches, the comined dt giving men of 4-2 lrve per dult for oth exhusted nd control insects (Tle 4). Tle 4. Men survivl times of phids strved t 20 0 C. nd 70% R.H. {Expts. 6-) Jxpt. no. 6 I Men Survivl times* (hr.) '3 Exhusted phids Hind tii length (mm.) i-' <r) *041 0*041 Expt. no. 6 2 Survivl time* (hr.) 67* ' *047 Men 55-2 Includes flight times. Control phids IO-2 Hind tii length (mm.) I-i6o I i

5 Viility nd fecundity of lte lenicole of Aphis fe Adult ge (dys) Adult ge (dys) Fig. 2. Accumultive totl numer of lrve produced per phid s function of dult ge; ech point represents the men of tch. A, Exhusted phids; B, control phids. Mortlity of nymphs orn of flight-exhusted phids Dt in the preceding section show tht exhustive flight hd no dverse effects on the development nd irth of lrve crried during flight, or on further emryogenesis. Nor ws the viility of these lrve ffected, for pre-dult mortlity of lrve orn

6 16 A. J. COCKBAIN during the first week fter flight in Expt. i ws similr in oth exhusted nd control tches. Of 437 nd 45 lrve orn to the exhusted nd control phids respectively, 9 (2-1 %) nd (i- %) filed to complete development. Tle 5. Numer of lrve deposited y the exhusted nd control phids tht survived the reproductive period (Expts. 1-5) Exhusted phids Control phids Btch no. \ i 2 Reproductive period (dys) % reching post-reproductive period S 7-S Men no. lrve/phid Btch no. IC id 2C zd Reproductive period (dys) % reching post-reproductive period 7-S 3-3 Men no. lrve/phid 99 o d 23 7-S A" AC Ad 26 IOO-O Men Sd Men S-o CONCLUSIONS C. G. Johnson (1.957) nc * Tylor (195) showed tht the verge durtion of flight of phids in the field is proly of the order of 1-3 hr.; similr times for phids flying freely in flight chmer were recorded y Kennedy nd Booth (1956). In the present study the phids wereflown tethered to pins for 3-9 hr., to pprent exhustion of the ville flight reserves; such flights, providing the phids lter settled nd fed on host plnt, hd no dverse effects on their susequent life. The rte t which flight reserves re consumed my differ in free nd tethered flight; 1 hr. of tethered flight my not e equivlent in terms of energy expenditure to 1 hr. of nturl flight. Nevertheless, it ppers unlikely tht prolonged flight in the field lowers the viility (see lso Tylor, i960) or reproductive potentil of phids; provided tht n phid lights on suitle host, length of life nd fecundity re unlikely to e ffected y flight durtion. Most nturl migrnts tht experience prolonged flight nd fil to light on host plnt, or other plnt from which they cn derive some nourishment, proly live for only short time. Results indicte tht few my e le to tke-off on the following dy; the first few seconds of flight is then similr in some respects to first flight, i.e. upwrds towrds light (C. G. Johnson, 1955); these phids would hve nother chnce to light on suitle host. Those phids tht were flown to exhustion nd then llowed to settle nd feed on young en plnts in drkness mde no ttempt to fly when exposed to light on the second dy; some could not do so even when stimulted, possily ecuse of the erly onset of flight-muscle utolysis. It is resonle to infer tht nturl migrnt of A. fe, lighting on suitle host fter n exhustive flight, would not fly gin.

7 Viility nd fecundity of lte lienicole of Aphis fe 17 SUMMARY 1. Lortory-rered 24 hr.-old lte lienicole of A. fe were flown for vrile periods, ut ll to pprent exhustion; their susequent longevity nd fecundity on rod ens, or their survivl times during strvtion, were compred with controls. 2. Adult longevity, reproductive rte nd cpcity, nd nymph viility were similr in exhusted nd control phids tht settled on host plnts fter flight. Men dult life ws 31 dys in exhusted phids nd 32 dys in the controls. Both exhusted nd control phids produced n verge of 4 lrve per dult. 3. The only mjor difference noted etween exhusted nd control phids tht fed fter flight ws reluctnce, or inility, of exhusted phids toflyon the following dy. 4. Exhusted phids strved fter flight lived for significntly shorter time (men of 30 hr.) thn control phids strved without flight (55 hr.). 2 % df the exhusted nd % of the control phids could tke-off on the next dy. 5. The results indicte tht long migrtory flights re unlikely to ffect the reproductive potentil of phids, nd tht lte lienicole of A. fe, hving settled on suitle host fter n exhustive flight, re unlikely to fly gin. I m most grfeful to Mr L. R. Tylor for his dvice nd encourgement during the course of the work, nd to Dr C. G. Johnson nd Dr K. Mellny for reding nd criticizing the mnuscript. REFERENCES COCKBAIN, A. J. (1961). Fuel utiliztion nd durtion of tethered flight in Aphis fe Scop. J. Exp. Biol. 3, JOHNSON, B. (1957). Studies on the degenertion of the flight muscles of lte phids. i. A comprtive study of the occurrence of muscle rekdown in reltion to reproduction in severl species. J. Ins. Physiol. 1, JOHNSON, B. (195). Fctors ffecting the locomotor nd settling responses of lte phids. Anim. Behv. 6, JOHNSON, C. G. (1955). Ecologicl spects of phid flight nd dispersl. Ann. Rep. Roth. Exp. St. pp JOHNSON, C. G. (1957). The verticl distriution of phids in the ir nd the temperture lpse rte. Qurt. J. R. Met. Soc. 3, KENNEDY, J. S. (195). The experimentl nlysis of phid ehviour nd its ering on current theories of instinct. Proc. Xth Int. Congr. hnt., Montrel, 2, KENNEDY, J. S. & BOOTH, C. O. (1956). Reflex nd Instinct. Discovery, 17, TAYLOR, L. R. (1957). Temperture reltions of tenerl development nd ehviour in Aphis fe Scop. J. Exp. Biol. 34, TAYLOR, L. R. (195). Aphid dispersl nd diurnl periodicity. Proc. Linn. Soc. Lond. 169, TAYLOR, L. R. (i960). Mortlity nd viility of insect migrnts high in the ir. Nture, Lond., 16, 410. WIGGLESWORTH, V. B. (1949). The utiliztion of reserve sustnces in Drosophil during flight. J. Exp. Biol. 26,

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