L. B. Milne and M. J. Milne.
Caddis Flies (Trichoptera) and Pitcher Plants.
Psyche 51(3-4):179-182, 1944.

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19441
Caddis Flies and Pitcher Plants
CADDIS FLIES (TRICHOPTERA) AND
PITCHER PLANTS
BY LORUS J. MILNE AND MARGERY J. MILNE
University of Pennsylvania and Beaver College Do caddis worms ever live in the leaf pitchers of pitcher plants? Is the microhabitat formed by the water in a pitcher plant leaf suitable for the larval stages of Trichoptera? This question is opened by the discovery of cases? adults and living eggs of Trichoptera in leaves of the pitcher plant? Sawacenia purpu~ea.
During casual inspection of pitcher plant leaf contents? larval cases obviously of trichopterous origin were discovered in late July at Robinson's Lake, near Irondale (Haliburton County)? Ontario? Canada? by the writers, This is a hilltop lakel lying in a rocky depression? fed by rains and emptied by evaporation or by overflow if the level rises sufficiently to reach the low rim. The margins of the lake are largely boggy? where Sphagnum has built a floating web enmeshing waterlogged stumpsl half rotted trunks and on which grows a dense mass of laurel and cranberry? with round-leaved sundew and pitcher plants in clumps at intervals. The water of the lake is very dark coffee coloredl and the bottom is a tangle of waterlogged branches from trees.
The first cases discovered were in dead? closed pitchers at the base of plants at least eight inches above lake level. The cases were dry and empty. The writers immediately postulated that the caddis worms must have crawled into the pitchers at some time when the lake wasl say, ten inches higher and the pitchers were flooded. At the time of observation, however? the lake was unusually high from recent, frequent and heavy rains. It was doubted by natives that the lake had been as high since the past spring? when the ice and snow broke up. Since the depth was greater than usual? the margin of the lake? where shallow enough for the bottom to be inspected through the dark colored water, was not the "normal1' lake area? and the com- plete lack of visible life there (including caddis cases) was not



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! 80 Psyche [Sept.-Dec.
surprising, The tangle of branches on the bottom of deeper parts of the lake made dredging impossible. On a return trip to the lake, almost every dead pitcher and '
every open living pitcher was inspected. Cases were iound in dead pitchers two feet above the high lake level, and in living pitchers at all levels. None of the cases contained law=, a few retaining a small number of sclerites, In two dead leaves, one remote from the water? one dose to it, sets of wings of Ptdn- st omix sp, (Phryganeid~; probab1y postka Wk, 1 were found. One green pitcher close to the water contained a partially di- gested caddis adult Limnephilidz; (Platycetztro@s indicans (?Vlk.) P while another green pitcher remote from the water contained a freshly dead Ptilo~tomis postica (Wlk,), The latter pitcher, and several other green leaves devoid of caddis cases and adults, contained fresh masses of living, partially devel- oped, caddis eggs. Judang from the size of the masses and their form, they were believed to be limnephilids, The cases were small, and of two types, usual~y not more than two cases being found in any one pitcher. Often where two
occurred, they were unKke in type. The cases were dl con- structed of Iawd and cranberry leaf pieces? many of which fall into the water of the pitchers and remain &we for a long while with little disintegration. The shorter type of case was cylin- drical, as much as a centimeter long, and about the same in outside diameter* The Ieaves were arranged with one edge tan- gential to the central tube, the leaves or piece< being very nu- merous, cemented together by their flat surfaces. The outside of this type of case was quite rough due to the irregular shape, size and position of the Ieaves composing it. The longer type
of case was roughly triangular in cross section, formed of fewer pieces of leaf, these with their flat surfaces tangential to the central tube. One or more larger pieces of leaf formed the base of the case, and to the edges of this base a low peaked roof was produced by two sheets of narrower, smaller leaf pieces ce- mented together dong the three corners. These cases were as much as seventeen millimeters in Iength, eight wide, four high, and of rather flimsy construction. Both cases were thought to be limnephilid structures, hut of species smder than any found dead in the pitchers. The triangular case type might be kpto- cerid in origin. Several cases were closed at one end as is com- monly done for pupation.




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19441 Caddis Flies and Pitcher Plants 181 The scanty evidence given above is highly suggestive that some species of limnephilid caddis flies have the habit~of laying eggs in July in water contained by leaves of Sarraceniq pur- purea, that the insects are able to escape from the pitchers) that the larvz live in the pitcher water and pupate there. Since the water contains proteolytic digestive substances, such a caddis worm would require an impermeable integument such as found in the pitcher plant mosquito wriggler (Wyeomyia smithii) and the larvz of the large fly) Sarcophaga sarraceni~. It is inter- esting to note in this connection that large maggots of the latter insect continued to squirm with life for over two hours in sev- enty percent alcohol, and it was not determined whether they died from alcohol penetration or from suffocation, since the low surface tension of the alcohol did not permit them to use their hydrofuge hairs for surf ace respiration. The writers were disappointed not to be abIe to obtain a definite answer on this matter, but the brevity of wartime vaca- tions and the limitations in pitcher plant supply cut their in- vestigations short. They hope that some readers of the present paper, having a nearby supply of Sarracenia purpurea (or other pitcher plant) will be able to get the answer to this interesting problem. They will be happy to assist anyone in the identifica- tion of larvz, pupz (preferably) or adults of Trichoptera found in pitcher plants.
Bibliography
Hubbard, H. J. 1896. Some insects which brave the dangers of the pitcher plants. Proc. Ent. SOC. Wash. 3 : 3 14-3 16. Jones, F. M. 1904. Pitcher plant insects. Ent. News 15 : 14-1 7. 1907. Pitcher plant insects 11. ibid. vol. 18:413-420. 1908. Pitcher plant insects 111. ibid. vol. 19: 150-1 56. 19 18. Dohriphora venusta Coquilett (Diptera) in Sarra- cenia fiava. ibid. vol. 29 : 299-302.
192 0. Another pitcher-plant insect (Diptera) Sciariz) . ibid. VOL 3 1 : 9 1-94.
192 1. Pitcher plants and their moths. Nat. Hist. 2 1 : 2 96- 3 16.
1935. Illustrations of North American Pitcher Plants, by Mary Vaux Wolcott (Smithsonian Inst. of Wash.), pp. 25-34.




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182 Psyche [Septa-Dec.
Lloyd, F. E. 1942. Carnivorous Plants. (Chronica Botanica Press) ; Sarracenia spp. pp. 1V-38, bibliography pp. 38-39.
I
Mitchell, E. G. 1905. Notes on the larva of the pitcher plant mosquito. Can. Ent. 3 7 : 332.
Sleight, C. E. 1913. Relations of Trichoptera to their environ- ment. Journ. N. Y. Ent. SOC. 2 1 : 4-8.




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