Studying Effects of Natural Enemies on Survival of Monarch Butterfly Larvae (Danaus

plexippus) to Aid in Monarch Conservation

Emily Nimmer

2007

Monarch Butterflies (Danaus plexippus)

http://www.calliebowdish.com/Pictures/Butterflypicture-8.jpg

North-Central Population Migration Pattern

(http://www.monarchlab.umn.edu/biology/gen3-4.aspx)

North-Central Population Migration Pattern

(http://www.monarchlab.umn.edu/biology/gen3-4.aspx)

Western Population:

500 miles

North-Central Population Migration Pattern

(http://www.monarchlab.umn.edu/biology/gen3-4.aspx)

3,000 miles

Purpose

• To investigate monarch larvae mortality due to the natural controls of predation and parasitism

First Goal

• To identify factors that influence mortality rates of monarch eggs and larvae

Background: First Goal

• Prysby (2004) showed only 5% of monarch eggs survive a 24-hour period when exposed to aphids

Background: First Goal

• Prysby (2004) showed only 5% of monarch eggs survive a 24-hour period when exposed to aphids

• Oberhauser (2003) showed that aphids are known to attract ants

Background: First Goal

• Prysby (2004) showed only 5% of monarch eggs survive a 24-hour period when exposed to aphids

• Oberhauser (2003) showed that aphids are known to attract ants

• Oberhauser (2003) also showed that ants are predators of monarch eggs and larvae

Ants Tending Aphids

http://www.discoverlife.org/IM/I_ANT/0000/320/Forelius_pruinosus,_workers_tending_milkweed_aphids,I_ANT74.jpg

Methods for First Goal:Falcon Heights Park, MN

(http://maps.google.com )

Monitoring Monarch Larvae

Photo by Author

Monitoring Presence of Aphids

Photo by Author

Monitoring Herbivory

Photo by Author

Factors in Monarch Larvae MortalityInstar Stage vs. Cause of Death (chi-square value=21.577, df=6,

p=0.00144)

0

20

40

60

80

100

120

140

160

Unknown Gone Egg SuckedOut

Egg Chewed

Cause of Death

Number of Monarch Eggs/Larvae

EggsFirst-InstarsSecond-Instars

Factors in Monarch Larvae MortalityPresence of Aphids

0

20

40

60

80

100

120

140

160

180

0 1–10 10–100 100–1000 > 1000

Number of Aphids

Number of Eggs

Dead

Alive

0

5

10

15

20

25

30

0 1–10 10–100 100–1000 > 1000

Number of Aphids

Number of First Instars

Dead

Alive

0

5

10

15

20

25

30

0 1–10 10–100 100–1000 > 1000

Number of Aphids

Number of Second Instars

Dead

Alive

Egg Survival vs. Presence of Aphids (chi-square value=17.953, df=4, p=0.00126)

Second-Instar Survival vs. Presence of Aphids (chi-square value=4.05, df=4, p=0.399)

First-Instar Survival vs. Presence of Aphids (chi-square value=9.87, df=4, p=0.0428)

0

10

20

30

40

50

60

0 <5 5–25

Percentage of Herbivory

Number of Second Instars

Dead

Alive

0

10

20

30

40

50

60

70

0 <5 5–25

Percentage of Herbivory

Number of First Instars

Dead

Alive

0

50

100

150

200

250

0 <5 5–25

Percentage of Herbivory

Number of Eggs

Dead

Alive

Factors in Monarch Larvae MortalityHerbivory

Egg Survival vs. Herbivory of Milkweed Plant (chi-square value=10.386, df=2, p=0.00556)

Second-Instar Survival vs. Herbivory of Milkweed Plant (chi-square value=3.254, df=2, p=0.197)

First-Instar Survival vs. Herbivory of Milkweed Plant (chi-square value=10.358, df=2, p=0.00563)

0

5

10

15

20

25

30

35

Apex Buds of Plant Bottom of Leaf Top of Leaf

Position of Larvae on Milkweed Plant

Number of Second Instars

Dead

Alive

0

10

20

30

40

50

60

Apex Buds of Plant Bottom of Leaf Top of Leaf

Position of Larvae on Milkweed Plant

Number of First Instars

Dead

Alive

0

50

100

150

200

250

300

Apex Buds of Plant Bottom of Leaf Top of Leaf

Position of Eggs on Milkweed Plant

Number of Eggs

Dead

Alive

Factors in Monarch Larvae MortalityPosition of Monarch Larvae on Milkweed Plant

Egg Survival vs. Position of Larvae on Milkweed Plant (chi-square value=4.251, df=3, p=0.236)

Second-Instar Survival vs. Position of Larvae on Milkweed Plant (chi-square value=0.548, df=3, p=0.908)

First-Instar Survival vs. Position of Larvae on Milkweed Plant (chi-square value=5.777, df=3, p=0.123)

Second Goal

• To determine mortality and survival rates of monarch eggs and larvae

Background: Second Goal

• Borkin (1982) and Prysby et. al (2001) focused on overall instar mortality

Monarch Larvae Instar Stages

(http://www.mlmp.org/monitoring/Guide/InstarImages/5_instars_c.jpg)

Egg

(http://www.mlmp.org/monitoring/Guide/InstarImages/5_instars_c.jpg)

First-instar

(http://www.mlmp.org/monitoring/Guide/InstarImages/5_instars_c.jpg)

Second-instar

(http://www.mlmp.org/monitoring/Guide/InstarImages/5_instars_c.jpg)

Third-instar

(http://www.mlmp.org/monitoring/Guide/InstarImages/5_instars_c.jpg)

Fourth-instar

(http://www.mlmp.org/monitoring/Guide/InstarImages/5_instars_c.jpg)

Fifth-instar

(http://www.mlmp.org/monitoring/Guide/InstarImages/5_instars_c.jpg)

Methods for Second Goal

Falcon Heights Park, MN(http://maps.google.com )

Monitoring Monarch Larvae

Survival of Monarch Eggs & Larvae

Figure 17: Survival of Monarch Larvae to Third Instar

0

50

100

150

200

250

300

350

400

1 2 3 4 5 6 7 8 9 10

Day

Number of Eggs/Larvae

EggsFirst-InstarSecond-InstarThird-Instar

Third Goal

• To determine the rate of parasitism of monarch larvae by tachinid flies (Lespesia archippivora)

Tachinid Fly (Lespesia archippivora)

Photo by Kaitlyn Creasey

Background: Third Goal

• Creasey (2007) showed that monarch larvae are killed every time they are parasitized by a tachinid fly

Background: Third Goal

• Creasey (2007) showed that monarch larvae are killed every time they are parasitized by a tachinid fly

• Prysby (2004) found tachinid parasitism rates in TX, WI, and LA between 11.5 and 43%– Also cited tachinid parasitism in Mexico between

70 and 98%

Background: Third Goal

• Creasey (2007) showed that monarch larvae are killed every time they are parasitized by a tachinid fly

• Prysby (2004) found tachinid parasitism rates in TX, WI, and LA between 11.5 and 43%– Also cited tachinid parasitism in Mexico between

70 and 98%

• Creasey (2007) and Oberhauser et al. (2007) found tachinid parasitism rates in MN between 6 and 13% for 2000-2006

Methods for Third Goal

(http://geography.about.com/library/blank/mn.jpg & modified by author)

Tachinid Fly Parasitism

Number of Monarch Larvae

Number of Larvae

Parasitized

Number of Tachinid

Flies Hatched

123 5 8

Conclusions

• Predation in eggs and first-instars can be related to ants

Conclusions

• Predation in eggs and first-instars can be related to ants

• 3% of eggs laid by one female survive to third-instar stage

Conclusions

• Predation in eggs and first-instars can be related to ants

• 3% of eggs laid by one female survive to third-instar stage

• 4% of monarch larvae parasitized by tachinid flies

Future Work

• Continue predation research on third-, fourth-, and fifth-instar larvae

Future Work

• Continue predation research on third-, fourth-, and fifth-instar larvae

• Monitor tachinid fly parasitism to further understand tachinid cycles

• Team Research• Alma de Anda• Reba Betalden• Dr. Karen

Oberhauser• Monarch Lab• Lois Fruen

Acknowledgements

Studying Effects of Natural Enemies on Survival of Monarch Butterfly Larvae (Danaus

plexippus) to Aid in Monarch Conservation

Emily Nimmer

2007