Questions and assignments to [1]Lecture 6

   1. Build a life table for an aphid population (aphids reproduce
   parthenogenetically). Estimate lx, dx, mx, Ro, T, and r. (See a [2]picture of
   aphids!)

   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, [3]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 [4]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 ([5]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.

   Estimate mortality caused by each natural enemy, convert it into k-value. Check
   that the sum of all k-values is equal to the total k-value for sawfly cocoons.
   Write results in the table, putting mortality processes in the order of their
   operation.

   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 [6]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 [7]gypsy moth mortality due to [8]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) [9]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!).

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     ____________________________________________________________________________

   [13]Alexei Sharov 1/11/96

References

   1. http://alexei.nfshost.com/PopEcol/lec6/lifetab.html
   2. http://axp.ipm.ucdavis.edu/PMG/D/I-HO-DPLA-IF.001.html
   3. http://www.forst.uni-muenchen.de/LST/ZOO/PHERODIP/DIPRIONIDAE/NEODIPRIONSERTIFER/neodiprion.sertifer.html
   4. http://www.forst.uni-muenchen.de/LST/ZOO/PHERODIP/DIPRIONIDAE/PARASITOIDS/parasitoid_images.html
   5. http://www.forst.uni-muenchen.de/LST/ZOO/HEITLAND/PONLINE/DIPTERA/TACHINIDAE/tachinidae.html
   6. http://alexei.nfshost.com/~sharov/insect/webworm.html
   7. http://www.gypsymoth.ento.vt.edu/slides/biglarv.jpeg
   8. http://www.gypsymoth.ento.vt.edu/slides/viruskilled.jpeg
   9. http://www.gypsymoth.ento.vt.edu/slides/pupa.jpeg
  10. http://alexei.nfshost.com/PopEcol/lec6/stagedep.html
  11. http://alexei.nfshost.com/PopEcol/lec6/lifetab.html
  12. http://alexei.nfshost.com/PopEcol/lec7/leslie.html
  13. http://alexei.nfshost.com/~sharov/alexei.html