Effect of Perezia pyraustae on oxygen consumption by the European corn borer, Ostrinia nubilalis

_Y.Insect Physiol., 1971, VoZ. 17, pp. 2457 to 2468. Pergamon Press. Printed in Great Britain

EFFECT OF PEREZ4 PYRAUSTAE ON OXYGEN CONSUMPTION BY THE EUROPEAN CORN BORER,

OSTRINIA LESLIE

C. LEWIS,l

NUBILALIS”

JOHN A. MUTCHMOR,2

and ROBERT

E. LYNCH1

lEntomology Research Division, A.R.S., U.S. Department of Agriculture, Ankeny, Iowa, and 2Department of Zoology and Entomology, Iowa State University, Ames, Iowa (Received

3 April 1971; revised 26 April 1971)

Abstract-Standard Warburg manometric techniques were used to determine the oxygen consumption by European corn borers, Ostrinia nubilalis, infected with Perezia pyraustae and by borers not infected with the protozoan. The curve of oxygen consumption for disease-free corn borers resembled that reported for other Lepidoptera; diseased corn borers had a slightly higher rate of consumption throughout the life cycle. INTRODUCTION

EXTENSIVEstudies have been made of the biology and histopathology of European corn borers, Ostrinia nubilalis (Hbn.), infected with Perexiu pyraustae Paillot, an obligatory intercellular microsporidian parasite (ZIMMACK et al., 1954; ZIMMACK and BRINDLEY,1957; KRAMER,1959a, b). The Malpighian tubules are the primary infected tissue in the late instar corn borer larvae, and the adult female harbours all stages of P. pyraustae in the genital tract. ZIMMACK and BRINDLEY(1957) and KRANIER(1959a) found that P. pyraustae shortened the post-pupal life of the corn borer and reduced fecundity. However, the effect of the inter-relationship between P. pyraustae and the European corn’borer on the general metabolism of the host has not been investigated. We therefore studied the oxygen consumption of European corn borers that were not infected with P. pyruustae (hereafter termed normal) throughout their life cycle and of borers infected with P. pyraustae (hereafter termed diseased). MATERIALS

AND METHODS

The European corn borer larvae used in this study were collected from corn stalk debris, colonized by the methods of GUTHRIEet al. (1965), and laboratoryreared in vials containing a wheat germ diet (LEWIS and LYNCH, 1969). The rearing incubators were maintained at 26.7”C and 75% r.h. with continuous light. To obtain normal insects, we heat-treated egg masses from the field-collected adults and from first generation laboratory-reared adults by the technique of RAUN (1961) to eliminate P. pyrawtae. This colony was then maintained free of disease throughout the test so we could determine oxygen consumption by normal borers. * Journal Paper No. J-6775 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 1687. 2457

24.58

LESLIEC. LEWIS,Jon.~ A. MIJTCHMOR, ANDROBERT E. LYNCH

The diseased insects were obtained from the same source, but they were artlficially infected with spores of P. pyraustae as follows: 300 newly hatched larvae were placed in a 10 in. dia. plastic rearing dish containing wheat germ rearing medium. Then 10 ml of a suspension of distilled water containing 40 x lo6 P. pyraustae spores/ml was dispensed over the medium. After one generation of mass rearing, this subcolony had become infected with P. pyraustae; it was then maintained in vials for the remainder of the study, A curve of oxygen consumption for the normal corn borers was then estabdished so comparisons could be made of the oxygen uptake by diseased borers because all previously published work on corn borer oxygen consumption had been done with diapausing insects (MUTCHMORand BECKEL,1959; BECK and MANEC, 1960; LYNCH and LEWIS, 1968; LYNCH, 1969). The oxygen consumption measurements were made with larvae from the day of hatch (before any feeding-designated larval day 0) through larval day 14. Work carried out in this laboratory (J. A. Jones, Iowa State University, private communication, 1970), has revealed that in the European corn borer the time that elapses between larval-pupal apolysis and larval-pupal ecdysis is less than 24 hr. To determine the beginning of larvalpupal apolysis or pupal-adult apolysis it is necessary to sacrifice the insect. Therefore, the times of larval-pupal ecdysis and pupal-adult ecdysis were used to distinguish the developmental stages of the European corn borer. Pupal oxygen consumption was measured from pupal day 1 through pupal day 7 (pupal day 1 was defined as the 24 hr period beginning at the time of the larval-pupal ecdysis). The oxygen consumption of adults was measured from adult day 1 through adult day 3 beginning with the day of pupal-adult ecdysis. From larval day 0 through larval day 6, more than 1 larva per flask was used for the measurements because the oxygen uptake was so low for each insect; these small larvae were discarded after each measurement. In all other determinations, a single insect was used. All larvae measured from larval day 7 through larval day 14 were allowed to pupate and were sexed so comparisons could be made between sexes. However, oxygen consumption was so low and the error involved in the determinations for larval day 0 through larval day 6 were so large that we used only larvae older than 6 days in determining the effect of P. pyraustae on oxygen uptake. Also after the manometry of diseased larvae, we determined the number of P. pyraustae spores/mg of tissue by the technique of RAUN et al. (1960). Therefore, no comparisons could be made between the sexes of diseased larvae. Standard Warburg manometric techniques (UMBREIT et al., 1964) were used. Five ml flasks were used with larvae and pupae of all ages and 15 ml flasks were used with larval day 7 or older and with pupae and adults. RESULTS Oxygen consumption by normal insects Larvae. The oxygen uptake of normal borers is presented in Table 1 and Fig. 1. It was highest (mm3 O,/mg per hr) during the early part of larval development and

EFFECT OF PEREZIA

PYRAUSTAE

ON OXYGEN

CONSUMPTION BY EUROPEAN CORNBORER24%

decreased (based on uptake/mg of tissue) as the body weight increased throughout larval life: At larval day 0, uptake/mg per hr was 12.43 ; at larval day 1 it increased to 19.79. Then it decreased steadily to 1.33 at larval day 14. This type of progression is normal (WIGGLESWORTH, 1965). For example, HSUEHand TANG (1944) TABLE I-A~EXAGII OXYGENUPTAKEANDWEIGHTOF NORMALCORNBORERS Oxygen uptake Age (days)

No. of observations

Larvae 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

54 58 46 50 45 94 66 67 82 62 63 62 98 100 77

mm3 O,/mg per hr + S.E.

12.43 + 6.89 19.79 rt 12.29 8*14_+ 4.04 13*10 + IO.45 4.43 + 2.80 4.12f I.78 5.33 -+ 2.37 2.27 _+ 1.66 3.04f I-38 2.05 + 0.95 2.26 + I,04 2.34_+ 0.70 I.95 ?I 0.57 I.68 + 0.53 l-33 I!z 0.29

Pupae and pharate adults : 1 101 0.99 k 0.27 2 68 O-64+ 0.32 3 6.5 O-62+ O-28 4 80 0.51 f 0.15 5 68 o-73 rt- O-18 6 69 0.94 Z!I O-23 7 60 0.90+ 0.27 Emerged adults : 1 65 2 67 3 65

2.09 *

0.53 0.67 l-33 + 0.52

I.90f

mm”O,/insect per hr + S.E.

2*37+ 1.44 2.27+ I.18 4-77 * 3.45 4*14f 3-56 7.27k 3.18 1.5.76+ 7.9 14.31 zk 7.83 36.93 f 18.31 41.86 + 23-74 73.62 rk29.28 94.77 Z!I27.12 145.99 t- 43.54 175.46 + 62.00 140.00 + 37-66 89.23 65.03 57.97 45.49 70.40 80.09 82.23

+ 26-3 1 rt 32.42 f 27.62 + 15.49 rf:21.32 i 26-25 F 30.33

111*14+43*14 87.97 136.13 58.42 _t 24.75

Weight (mg + SE.)

o-13 zk 0.04 0.28 + 0.05 0.3s+ o-07 O-96 + 0.16 1.79 rt: 0.37 3.00+ l-05 6*96+ 2.35 12.8 f 4.8 19.9 + 6.7 34.3 f 8-l 43.7 & 15.7 81.0 +21-s

98.6 + 18.2

107.0 z!I22.2 91.7 97.9 93.6 89.5 96.2 85.6 92.1

+17*9 i: 16-O + 17.4 f 15-T + 14.4 f 16.5 * 14.1

52.6 48.0 44.6

rt 14.4 + 13.6 + 13.9

Instar

First First Second Second Second Third Third Third Fourth Fourth Fourth Fourth Fifth Fifth Fifth

reported that newly hatched larvae of Bombyx mori (L.) consumed 2.95 mm3 O,/ mg per hr which decreased to 0.32 in the later stages of larval development; SLAMA (1959) reported a similar decline in oxygen uptake by several species of sawflies ; and EDWARDS (1970) reported the same pattern for Heliothis zzea (Boddie). When respiration was calculated as mm3 O,/insect per hr, the rate for 1 day old corn borer larvae was 2.37 (Table 1, Fig. 2). This rate increased to a high of

2460

LESLIE C. LEWIS, JOHN A. MUTCHMOR, AND ROBERT E. LYNCH

EFFECTOF PEREZIA PYRAUSTAE

ON OXYGEN

CONSUMPTION BY EUROPEAN CORNBORER2461

175.46 on day 13 and then declined to 140.00 on day 14. At the rearing conditions used in this study, the corn borer reaches a maximum in its feeding the twelfth and thirteenth day of larval life. Thus the peak in oxygen uptake the thirteenth day and the drop the next day corresponded to changes in physical activity indicative of the approaching larval-pupal apolysis followed, within 24 hr, by larvalpupal ecdysis. Respiration per unit weight by male and female corn borer larvae did not differ substantially from larval day 7 through larval day 14 (Table 2), and it was almost identical from day 7 through day 11 (Table 2). However, females consumed more oxygen the last 3 days of larval life than males which corresponded with the greater increase in the weights of these females (Table 2). Pupae. Oxygen uptake as mm3 O,/mg per hr by pupae followed the typical U-shaped curve for pupal respiration (Table 1, Fig. 1). The low point occurred on pupal day 4, consumption increased through pupal day 6, and a slight drop occurred just before pupal-adult ecdysis. TAYLOR and STEINBACK(1931) reported a similar curve and a slight decrease before emergence, for Galleria mellonella (L.), but the final drop was greater than that we recorded for the corn borer. Also, a U-shaped curve for pupal respiration was reported by HSUEH and TANG (1944) for B. mori and by EDWARDS(1970) for H. xea. The first downward part of the curve reflects the period of histolysis and reorganization of tissue; the subsequent upward trend reflects the activity of the organized tissue. Likewise, histolysis and reorganization took place in corn borer pupae. By the time the pupae in our test reached pupal day 4, most of the tissues were formed (J. A. Jones, Iowa State University, private communication, 1970), and the activity of these tissues during the remainder of pupal life explains the increase in oxygen consumption. Oxygen consumption as mm3/mg per hr was the same for the sexes throughout pupal life (Table 2), but, consumption as mm3/insect per hr was greater for females than for males, a reflection of the greater weights of female pupae. Both sexes exhibited the characteristic U-shaped curve of oxygen uptake, whether the calculations were based on per unit weight or uptake per insect. Again, this curve probably reflects initial histolysis and reorganization and then activity of organized tissue. Adults. At adult day 1, the borers had an increase in oxygen uptake over that for pupal day 7, 2.09 mm3 O,/mg per hr compared with 0.90 mm3 (Table 1 and Fig. 1) as a result of increased activity. Thereafter, the rate declined gradually in correspondence with the decline in overall activity of the ageing adults, The same result was obtained when respiration was calculated as consumption per insect (Table 1, Fig. 2). The oxygen uptake per insect for males and females during the pupal and adult stages is presented in Table 2 and Fig. 3. Females had a sharper increase in oxygen uptake from pupal day 5 through pupal day 7 and adult day 1, the period when ovarian tissue was developing rapidly. However, the general decline during the adult stage was similar in both sexes. Since adults live 4 to 6 days at the conditions of our test, ageing probably accounts for this decline.

(62) (34) (31) (58) (37) (38) (35)

(25) (46) (26) (27) (29) (59) (58) (45)

82.31 f 27-66 (34) 68.64 + 28.28 (33) 47.78 + 17.04 (30)

f 23.12 + 23.52 + 23.99 ?c13.69 rt:16.45 f 13.75 + 18.79

Pupae and pharate adults : 1 84.32 2 56.37 3 49.25 4 40.53 5 57.61 6 62.80 7 67.69

Emerged adults : 1 2 3

+ 7.93 + 17.58 f 26.91 rtr33.12 + 27.08 f 42.03 f 54.34 f 30.83

Third Fourth Fourth Fourth Fourth Fifth Fifth Fifth

Larvae : 7 8 9 10 11 12 13 14

Male

13.53 36.07 41.36 77.40 95.60 138.27 145.61 124.51

Instar

Age (days)

) 29.06 + 37.40 rfr28.29 zk 11.93 + 15.69 f 21.55 + 31.66

+ 7.89 i 18.80 + 21.58 & 23.93 ?z27.71 f 43.11 + 49.54 + 35.85

(39) (34) (34) (22) (31) (30) (25)

(36) (34) (33) (30) (23) (39) (39) (30)

142.77 f. 33-94 (31) 109.37 f 22.59 (34) 68.09 f 26.00 (33)

97.04 73.69 65.93 58.56 85.67 101.99 102.60

14.98 38.03 41.68 74.73 97.70 157.70 214.96 162.46

Female

Oxygen uptake (mm” OS/insect per hr If:S.E.)

+ 0.25 rk0.27 rt 0.27 1: o-17 + 0.19 + O-21 + 0.24

2.06 + 1.78 2-05 t O-85 1.46 f O-52

1.05 0.65 0.61 0.50 0.67 0.87 0.84

2.10 f 1.33 3.02 + 1.25 2.06 + 1.00 2.56 rt 1.32 2.28 f 0.66 1.90 k 0.63 1.53 + 0.55 1.34 + 0.30

Male

+ 0.26 zkO-32 t 0.29 f 0.10 *o-15 2 0.23 * 0.30

2.14 zk0.43 1.76 ri O-36 1.21 + 0.48

0.89 0.64 0.63 0.54 0.79 1.02 0.99

2.38 f 1.89 3.06 f 1.54 2.06 i 0.94 2.10 + 0.64 2.37 + 0.68 2.02 + 0.45 1.87 + 0.44 1.30 + 0.28

Female

Oxygen uptake (mm” O,/mg per hr + S.E.)

9.18 7.80 9.87 9.26 7.12 4.59 5.87

40.0 + 5.4 33.6+ 2.5 32.8 k 2.9

80.21 86.9+ 80.6+ 82.4+ 85*8+ 72.3 + 81.8 f

6.8 k 2.4 12.75 5.1 19.6 + 6.7 31.52 7.0 44.4 * 16.6 74.9 ?c 17.6 95.3 f 10.8 93.1 f 11.0

Male

66.5 + 6.0 62.2 I 6.5 56.5 z?c 9.3

109.9 A 12.7 115*9+ 7.4 105.9 i 13.6 108.4 + 10.6 108.6 I!-10.6 101.2 AZ10.9 106.3 I 8.8

7.1 _+ 2.3 13.25 4.4 20.05 6.8 36.4f 8.2 43.4 z!C 14.5 82.0 + 5.3 116.6 + 18.8 127.2 rf:18.1

Female

Weight (mg) +_S.E.

TABLE ~-AVERAGE OXYGENUPTAKEAND WEIGHTOF NORMALMALEAND FEMALECORNBORERS(number of insects in parentheses)

;I 2 8

z

8 8 “’ g s 8 S$

;

2 $

g “!

r

G .P

K

r;: is

EFFECT

OF

PEREZIA PYRAUSTAE

123’Q567

ON OXYGEN

CONSUMPTION

0

111lllllll

EUROPEAN

CORN

BORER

2463

1234567123.

123

I PUPAL-ADULT ECDYSIS DAYS AFTER RESPECTIVEECDYSIS

LARW';;AL

LAk$X-Pf;AL

30

BY

t

1234567123

PUPAL-ADULT LARVAL-PUPAL ECDYSIS ECDYSIS DAYS AFTER RESPECTIVEECDYSES

I LAY;;.-AtPAL

DAYS AFTER RESPECTIVEECDYSIS

II

III

I1111

1234567123

LARVAL-PUPAL PU~$-$l~LT ECDYSIS DAYS AFTER RESPECTIVEECDYSIS

FIG. 3. Oxygen uptake by normal or diseased male and female corn borers during the pupal and adult stages. Upper left: closed circles represent values for diseased females; closed triangles represent values for diseased males. Upper right: open circles represent values for normal females; closed circles represent values for diseased females. Lower left: open circles represent values for normal females; closed squares represent values for normal males. Lower right: closed squares represent values for normal males; closed triangles represent values for diseased males.

4

2464

LESLIE C. LEWIS, JOHN A. MIJTCHMOR, AND ROBERT E. LYNCH

Oxygen consumption by infected insects Lamae. Oxygen uptake/mg per hr by diseased corn borers is given in Table 3 and Fig. 4. As explained, all data for diseased larvae begin on larval day 7 when the borers consumed 6.82 mm3 O,/mg per hr. The rate then gradually decreased to 2.06 on larval day 14. Uptake per insect by diseased borers produced a curve

115 lo9-

p

HATCH LARVk&'$SL

8-

PU'U/@DULT

DAYS AFTER HATCH AND RESPECTIVEECDYSES

7 8 HATCH

91011121314

12

3

LARVAL-PUPAL

4

5 6

7

1

2

3

PUPAI--ADULT

DAYS AFTER HATCH AND RESPECTIVEECDYSES

Standard deviations are shown by vertical lines. The inset figure shows a line of best fit drawn by eye through the points. FIG. 4. Oxygen uptake by diseased corn borers.

similar to that for normal insects except at a few points (Fig. 2). Thus, diseased borers had a slightly higher respiration rate on larval days 7, 8, 9, 11, and 14 and reached their maximum oxygen uptake at larval day 14. Apparently the infection by the protozoan was increasing the developmental time of the corn borer larvae. Pupae. Pupal respiration as mm3 0,jmg per hr by diseased insects also exhibited the normal U-shaped curve and the slight drop before pupal-adult ecdysis (Table 3, Fig. 4). The same results were obtained when the data were calculated as uptake per insect (Fig. 2), but diseased pupae generally had a slightly higher rate of oxygen uptake than the normal pupae. The data for diseased male and female pupae are presented in Table 4 and Fig. 3. No large differences were apparent between sexes as uptake per unit weight or as uptake per insect (Fig. 3). Males and females had respiratory rate curves of the same shape, but the magnitude of female respiration was always greater. Adults. Adult borers had an increased oxygen uptake on adult day 1 (Table 3 and Figs. 2, 4) compared with the day prior to pupal-adult ecdysis. Thereafter,

67 66 67 68

11 12 13 14

67

3

2

66 68

1

Emerged adults :

Pupae and pharate adults: 85 1 83 2 83 3 85 4 84 5 85 6 85 7

72 65 68 65

No. of observations

Larvae : 7 8 9 10

Age (days)

* 0.44 iz O-31 + 0.50 + 0.40 + 0.44 _t o-33 +_0.33

f 3.90 + 2.18 1 l-45 &-1.56 rt:l-42 +_0.81 + 0.82 _t 0.50

per hr f S.E.

2-55 + 1.11

2.32 $I0.60 2.21 ?Io-94

1.03 0.87 0.68 0.88 0.89 1.01 0.92

6.82 3.93 3.53 3.58 2.61 2.38 2.20 2.06

mma O,/mg

+_41.26 _+25.28 + 43.80 i: 33.19 +_36.75 + 30.68 f 31.93

+ 16.04 + 24.87 + 31.12 +_28.28 + 34.57 + 70.19 + 65.42 ) 57.99

87.84 + 28.48

110.93 f41-65 88.26 k 38.68

88.83 71.17 56.32 68.83 69.77 88.62 75.70

28.44 44.97 69.49 62-52 65.77 181.99 171.11 203.23

mm3 O*/insect per hr Z!Z SE.

Oxygen uptake

82.7 81.9

3.48 4.11

6.66

38-l

48.4 41.6

78.6 78.1

3.49 3.44

6.42 6.38

87.4

77.9 80.1 98.1

0.81 1.26 l-16

82.3 81.0

19.1 26.0

1.28 0.94

3.30

20.1

0.97

3.39 4.11

4.7 11.8

0.82

3.3

+_12*8

+ 14.4 k12.5

f15.6

+ 15.6

+ 14.2 c 12.6

+ 12.2 13.8 L!Z

k14.9

z!z24.6 +22*0 + 17.8

+ 8.3 _+ 5.9

+ 6.2

+

+ 1.8

Weight (mg) + SE.

O-67

Spores ( x 105/mg)

TABLE 3-AVERAGR OXYGENUPTAKE,WEIGHT, AND sPoRRs/mg OF CORN BORERSINFECTEDWITH P. pyraustae

Fifth Fifth Fifth

Third Fourth Fourth Fourth Fourth

Instar

B

$

0” !z

5

s ._

8

2

i

8 2 2 z

1 z

2 7 F $j

_(

iz

k 6 *a c1

2

OXYGEN

UPTAKE

AND

Male

Emerged adults : 1 87.40 _+24.93 (33) 2 75.95 + 31.45 (34) 3 86.86 + 24.92 (33)

134.35 +41-72 (33) 100.56 + 41.22 (34) 88.84 + 31.53 (34)

97.58 + 39.91 76.83 +I24.31 74.34 + 45.80 78.29 z!z38-11 86-27 _+40-22 96.09 f 33.89 9.5-53 f 34.68

Female

(50) (32) (28) (25) (20) (36) (35)

WEIGHT

Oxygen uptake (mm3 O,/insect per hr + S.E.)

~-AvERAGR

Pupae and pharate adults : 1 76.34_+ 39.91 (35) 2 67.62 + 25.23 (51) 3 47.15 rt 39.72 (55) 4 64.89 + 30.04 (60) 5 64.61 f 33.99 (64) 6 74.46 f 24.30 (49) 7 63.23 + 22.66 (SO)

Age (days)

TABLE

FEMALE

CORN

in parentheses)

AND

2.43 AZ0.59 2.43 + 0.87 3.26 I!I1.04

l-05 + 0.48 O-91 2 0.33 0.63 + 0.51 0.90 _+0.40 O-89 L!Z 0.46 1.04 + o-33 0.89 f 0.34

Male

zko-41 + 0.24 I!C 0.47 _+0.41 + O-36 + 0.31 r!z0.31

2.21 + 0.60 1.99 rt o-95 1.86 + O-66

1.02 0.81 0.78 0.84 0.89 0.98 0.95

Female

Oxygen uptake (mm3 02/mg per hr k S.E.)

OF MALE

+ 8.9 -I:7.4 + 5-4 f 8.0 + 6.5 f 7.6 + 7.6

36.1 ?r:5.6 31.0 iz4.8 27.1 + 3.2

75.7 74.7 74.2 72.1 72.5 71.9 71.3

WITH

+ 12.4 -I 13.2 _+10.5 k 13.5 rt:IO-8 + 11.3 IL11.0

60.8 + 8.9 52.2 + 7.9 48.7 + 9.0

95.7 94.2 94.5 94.3 95.9 97.3 97-l

Female

6.95 8.34 8.45

3.77 4.02 4.30 3.73 3.38 3.32 4.45

Male

2.98 2.38 3.74 2.90 3.67 3.69 3.61

Fez

Spores (x l@/mg)

P. pyraustae (number of insects

Weight (mg) +- S.E.

INFECTED

Male

BORERS

?p

Fs

5 ”

2

6

;

2

5 3

C

kd E

EFFECT

OF

PEREZIA

PYRAUSTAE

ON OXYGEN

CONSUMPTION

BY

EUROPEAN

CORN

BORER

2467

this rate levelled off when it was calculated as uptake per unit weight (Fig. 4), but it dropped sharply on adult day 2 before levelling off on adult day 3 when it was calculated as uptake per insect (Fig. 2). When comparisons were made between sexes, the diseased adult males proved to have a much higher oxygen consumption than the diseased females (Table 4, Fig. 3), but at adult day 1 and 2 diseased males and females had respiratory rate curves of the same shape. On adult day 3, the oxygen uptake by the female dropped; the uptake by the male increased sharply (Fig. 3). Evidently, the greater infection of the males at this time (S-45 x lo5 spores/mg of insect tissue compared with 4.91 x lo5 sporesjmg of insect tissue for the females) produced the higher respiratory rates. DISCUSSION

At all times diseased borers oxygen uptake t-test indicated

during the life cycle of the corn borer, the oxygen consumption by was higher than that by normal borers. Fig. 5 compares the as mm3 O,/mg per hr by normal and diseased insects. Student’s a significant difference at the 1 per cent level of confidence between

7 8 9 1011121314 HAiCH

1 2 3 4 5 6 7 1 2 3

LARVAL-PUPAL ECYDYSIS

PUPAL-ADULT ECYDYSIS

DAYSAFTERHATCHAND RESPECTIVE ECDYSES 5. Comparisons of oxygen uptake by normal and diseased corn borers. Closed circles represent values for normal borers; closed triangles represent values for diseased borers.

FIG.

the two populations on larval days 7 and 9, pupal day 4, and adult day 3. Also, differences were significant between larval days 10 and 14 at the 5 per cent level of confidence. During the late instars of larval development, the insect consumes large amounts of food and is rapidly increasing its body-weight. Pupal and adult corn borers utilize their fat bodies as an energy source since there is no food intake. In the pupal and pharate adult period, there is a reorganization of tissue and a rapid development of the female reproductive system which requires large energy reserves. Between pupal days 2 and 5, the diseased female pupae consumed more 72

2468

LESLIEC. LEWIS, JOHNA. MUTCHMOR,AND ROBERTE. LYNCH

oxygen than the normal female (Fig. 3), that is, a greater amount of oxygen was consumed by the smaller insect, probably because of the additional stress of the disease on the female pupae. The data in this study indicate that P. pyraustae could therefore impose a stress on the borer during all developmental stages, and such a stress would doubtless contribute to greater oxygen consumption by diseased borers than by normal borers. Also, some of the increase in consumption must be attributed to the actual oxygen requirements of P. pyraustae. However, P. pyraustae is an obligatory parasite, so it is impossible to make meaningful measurements of its rate of respiration alone. REFERENCES BECKS. D. and HANECW. (1960) Diapause in the European corn borer, PyYausta nubilalis (Hiibn.). r. Insect Physiol. 4, 304-318. EDWARDSL. J. (1970) Oxygen consumption by the corn earworm, Heliothis zea. Ann. ent. Sot. Am. 63, 773-777. GUTHRIEW. D., RAUN E. S., DICKE F. F., PESHOG. R., and CARTERS. W. (1965) Laboratory production of European corn borer egg masses. Iowa StateJ: Sci. 40, 65-83. HSUEHT. Y. and TANG P. S. (1944) Physiology of the silkworm-I. Growth and respiration of Bombyx mori during its entire life-cycle. Physiol. Zool. 17, 71-78. KRAMER J. P. (1959a) Some relationships between Perezia pyraustae (Sporozoa, Nosematidae) and Pyrausta nubdalis (Hcbner) (Lepidoptera, Pyralidae). J. Insect Path. 1, 25-33. KRAMERJ. P. (195913) Studies on the morphology and life history of Perexia pyraustae Paillot (Microsporidia: Nosematidae) Trans. Am. microsc. Sot. 78, 336-342. LEWIS L. C. and LYNCH R. E. (1969) Rearing the European corn borer, OstGzia nubilalis (Hiibner) on diets containing corn leaf and wheat germ. Iowa StateJ. Sci. 44, 9-14. LYNCH R. E. (1969) Effect of decreasing photophase and temperature on oxygen consumption and survival of the European corn borer. Unpublished M.S. Thesis, Iowa State University of Science and Technology, Ames. LYNCH R. E. and LEWIS L. C. (1968) Effect of temperatures on the respiration of the European corn borer. PYOC. N. cent. Branch Ent. Sot. Am. 23, 37. MUTCHMORJ. A. and BECKELW. E. (1959) Some factors affecting diapause in the European corn borer, Ostrinia nubilalis (Hbn). (Lepidoptera: Pyralidae). Cun.~. Zool. 37,161-168. RAUN E. S. (1961) Elimination of microsporidiosis in laboratory reared European corn borer by use of heat. j?. Insect Path. 3,446-448. RAUN E. S., YORK G. T., and BROOKSD. L. (1960) Determination of Perezia pyraustae infection rates in larvae of the European corn borer. g. Insect Path. 2, 254-258. SL~A K. (1959) Total metabolism during the larval development in sawflies (Hym., Tenthredinoidea). Acta Sot. ent. Cechosloveniae 56, 113-125. TAYLOR I. R. and STEINBACK H. B. (1931) Respiratory metabolism during pupal development of Galleria mellonella (bee moth). Physiol. Zbol. 4, 604-619. UMBREIT W. W., BURRISR. H., and STAUFFERJ. H. (1964) Manometric Techniques 4. Burgess, Minneapolis. WIGGLESWORTH V. B. (1965) The Principles of Insect Physiology, 6th ed., Dutton, New York. ZIMMACKH. L., ARIXJTHNOTK. D., and BRINDLEYT. A. (1954) Distribution of the European corn borer parasite Perezia pyraustae, and its effect on the host. J. econ. Ent. 47, 641-645. ZIMMACKH. L. and BRINDLEYT. A. (1957) The effect of the protozoan parasite Perezia pyraustae Paillot and the European corn borer. y. econ. Ent. 50, 637-640.