Questions and assignments to Lecture 6

Age, days (x)	Number of survivals	Mean number of offsprings per parent
0	1000	0
1	900	0
2	820	0
3	750	0
4	680	0
5	620	0
6	550	1
7	500	2
8	450	5
9	400	10
10	350	12
11	300	10
12	250	8
13	200	6
14	100	3
15	50	1
16	0	0

2. Partial life-table. The European pine sawfly, Neodiprion sertifer, cocoons were collected at the beginning of August and dissected. Results of dissection of new (current year) cocoons are the following:

Healthy sawfly eonymph	144
Eaten by predators	125
Exit hole of parasitoid Drino inconspicua	15
Exit hole of parasitoid Pleolophus basizonus	78
Larvae of parasitoid Exenterus abruptorius	210
Exit hole or larvae of gregarious parasitoid Dahlbominus fuscipennis	23
Fungus disease	205
Total	800

Life-cycle information:

Excellent images of parasitoids are available from the PHERODIP homepage.

• Parasitoids D.inconspicua, P.basizonus and D.fuscipennis have several generations per year, whereas E.abruptorius has only 1 generation.
• D.inconspicua (Tachinidae) is an endoparasite and attacks larvae (4-5 instar). It emerges from the host immediately after host cocooning. It develops very fast and wins the competition with any other parasitoids.
• E.abruptorius is an ectoparasite, attacks host eonymphs a day prior to cocooning. Parasitoid larvae emerges inside the cocoon, eats the host and overwinters as larvae inside host cocoon. If the host was previously parasitized by D.inconspicua, then E.abruptorius dies.
• P.basizonus and D.fuscipennis attack host cocoons. They are ectoparasites. If another parasite (E.abruptorius) is already present in the cocoon, it will be eaten first. D. fuscipennis wins the competition with P.basizonus.

Simple example:

Healthy eggs	200
Desiccated eggs	100
Parasitized eggs	200
Total	500

Mortality process	Number of eggs in which this mortality process can be detected	Number of killed eggs	Mortality	Survival	k-value
1. Desiccation	500	100	0.2	0.8	0.223
2.Parasitism	400 (500-100)	200	0.5	0.5	0.693
Total	500	300	0.6	0.4	0.916

3. Estimate mortality in a predator-exclusion experiment. The fall webworm, Hyphantria cunea, larvae in colonies were counted at the beginning and at the end of experiment:
A. Control - without protection
B. Exclusion of large predators: prey were protected by a 1/2 inch cell hardware cloth
C. Exclusion of all predators: prey were protected by 1 mm cell mesh
Estimate: mortality caused by large and small predators, convert it to k-value.

	Initial larvae in 10 colonies	Larvae alive at the end
Control	3000	1400
Large predators excluded	3500	2900
All predators excluded	3200	3100

4. Estimate gypsy moth mortality due to virus (NPV).
Gypsy moth larvae were collected in the forest at 7-day intervals and placed individually in the cups with diet. Incubation period of viral infection (from infection till death) is 7 days. Estimate: total mortality caused by virus and the k-value.

	Collected larvae	Larvae that died in 7 days since collection
1-st week	200	23
2-nd week	200	7
3-rd week	200	5
4-th week	200	30
5-th week	200	58
6-th week	200	115

5. Estimate the rate of simultaneous mortality processes
Gypsy moth (Lymantria dispar) pupae are destroyed by small mammals and by invertebrates. 300 laboratory-reared pupae were placed on tree boles. Three days later, 200 of them were damaged by small mammals and 50 were damaged by invertebrate predators (Calosoma sycophanta). Each pupa can be eaten just once. Estimate mortality caused by each predator guild if another predator guild was absent (note: use k-values!).