[excerpt] On January 9, 1964, a larva of the hydrophilid beetle Tropister- nus,glaber (Herbst) was removed from an aquarium and placed in a fin- ger bowl of water along with a sprig of coontail (Ceratop7tyllum demer- sum Linnaeus). The plant provided support for the larva to reach the water\u27s surface. By accident rather than design it harbored the snail Physa sayii (Tappan), individuals of which were clinging to its leave

Willson, Ronald B.

English

ValpoScholar

The Great Lakes Entomologist 
Volume 1 
Number 1 -- July 1966 Number 1 -- July 1966 Article 2 
July 1966 
Interference of the Snail Physa Sayii with Equilibrium in 
Tropisternus Glaber (Coleoptera: Hydrophilidae) 
Ronald B. Willson 
Michigan State University 
Follow this and additional works at: https://scholar.valpo.edu/tgle 
 Part of the Entomology Commons 
Recommended Citation 
Willson, Ronald B. 1966. "Interference of the Snail Physa Sayii with Equilibrium in Tropisternus Glaber 
(Coleoptera: Hydrophilidae)," The Great Lakes Entomologist, vol 1 (1) 
Available at: https://scholar.valpo.edu/tgle/vol1/iss1/2 
This Peer-Review Article is brought to you for free and open access by the Department of Biology at ValpoScholar. 
It has been accepted for inclusion in The Great Lakes Entomologist by an authorized administrator of ValpoScholar. 
For more information, please contact a ValpoScholar staff member at scholar@valpo.edu. 
12 THE MICHIGAN ENTOMOLOGIST Vol. 1 
INTERFERENCE OF THE SNAIL PHYSA SAYll WITH 
EQUILIBRIUM IN TROPISTERNUS GLABER 
(COLEOPTERA: HYDROPHILIDAE) 
Ronald B. Willson 
Department of Entomology, Michigan State University 
East  Lansing, Michigan 48823 
On January 9, 1964, a larva of the hydrophilid beetle Tropister- 
nus,glaber (Herbst) was  removed f rom an aquarium and placed in  a fin- 
g e r  bowl of water along with a spr ig  of coontail (Ceratop7tyllum demer- 
sum Linnaeus). The plant provided support fo r  the l a rva  to reach the 
water ' s  surface. By accident ra ther  than design it harbored the snail 
Physa sayii (Tappan), individuals of which were  clinging to its leaves. 
On January 17, a mosophila l a rva  was given to the beetle, which 
immediately grabbed the prey, moved to the vegetation, and began in- 
gesting the meal. A second larva was offered when the f i r s t  was  fin- 
ished. The hydrophilid took it, too, with the mandibles, but this t ime 
did not move toward the vegetation. It thrust  i t s  anal spiracle up to the 
water ' s  surface and began moving about through swimming movements 
of the legs  and of the body, but no attempt was made to eat  the second 
prey. A s  a resul t  of the beetle 's  vigorous movements, a snail not pre-  
viously noted was dislodged f rom the side of the finger bowl. The snail 
extended its foot and attached itself to the dorsal thoracic region of the 
beetle. It then proceeded to crawl the length of the beetle larva before 
falling off the animalT s posterior. 
Following the above events, the Tropisternus was  noted to be i n  
dis t ress .  I ts  body was coated by mucus wherever the snail 's  foot had 
made contact, and i t s  legs  were  inextricably bound together by viscous 
s t rands  of mucus. The unfortunate l a rva  began violent contractions of 
the body, while attempting to keep the anal spiracle to the water ' s  sur-  
face. When i t s  legs  came in  contact with the surface film, a i r  bubbles 
attached to the mucous coating on them. The bubbles subsequently 
buoyed the venter, leaving the larva in  a state of imbalance. The in- 
sect  continued i t s  contortions, became separated f rom the surface film, 
and fell to the bottom of the finger bowl. The observer attempted r e s -  
cue by moving the larva to the Ceratophyllunz a t  the surface, where i t  
continued twisting and contracting the anterior portion of i t s  body while 
still attempting to separate i t s  legs. After a time it became motion- 
l e s s  and dropped the fly larva. It resumed the twisting and contorting 
and again fell to the bottom of the finger bowl. I t s  contortions contin- 
ued, with periodic lapses,  but surface fi lm contact was  never regained. 
Finally the Tropisternus died f rom suffocation. 
1
Willson: Interference of the Snail Physa Sayii with Equilibrium in Tropist
Published by ValpoScholar, 1966


Interference of the Snail Physa Sayii with Equilibrium in Tropisternus Glaber (Coleoptera: Hydrophilidae)

Valparaiso University

The Great Lakes Entomologist Volume 1 Number 1 -- July 1966 Number 1 -- July 1966 Article 2 July 1966 Interference of the Snail Physa Sayii with Equilibrium in Tropisternus Glaber (Coleoptera: Hydrophilidae) Ronald B. Willson Michigan State University Follow this and additional works at: https://scholar.valpo.edu/tgle  Part of the Entomology Commons Recommended Citation Willson, Ronald B. 1966. "Interference of the Snail Physa Sayii with Equilibrium in Tropisternus Glaber (Coleoptera: Hydrophilidae)," The Great Lakes Entomologist, vol 1 (1) Available at: https://scholar.valpo.edu/tgle/vol1/iss1/2 This Peer-Review Article is brought to you for free and open access by the Department of Biology at ValpoScholar. It has been accepted for inclusion in The Great Lakes Entomologist by an authorized administrator of ValpoScholar. For more information, please contact a ValpoScholar staff member at scholar@valpo.edu. 12 THE MICHIGAN ENTOMOLOGIST Vol. 1 INTERFERENCE OF THE SNAIL PHYSA SAYll WITH EQUILIBRIUM IN TROPISTERNUS GLABER (COLEOPTERA: HYDROPHILIDAE) Ronald B. Willson Department of Entomology, Michigan State University East  Lansing, Michigan 48823 On January 9, 1964, a larva of the hydrophilid beetle Tropister- nus,glaber (Herbst) was  removed f rom an aquarium and placed in  a fin- g e r  bowl of water along with a spr ig  of coontail (Ceratop7tyllum demer- sum Linnaeus). The plant provided support fo r  the l a rva  to reach the water ' s  surface. By accident ra ther  than design it harbored the snail Physa sayii (Tappan), individuals of which were  clinging to its leaves. On January 17, a mosophila l a rva  was given to the beetle, which immediately grabbed the prey, moved to the vegetation, and began in- gesting the meal. A second larva was offered when the f i r s t  was  fin- ished. The hydrophilid took it, too, with the mandibles, but this t ime did not move toward the vegetation. It thrust  i t s  anal spiracle up to the water ' s  surface and began moving about through swimming movements of the legs  and of the body, but no attempt was made to eat  the second prey. A s  a resul t  of the beetle 's  vigorous movements, a snail not pre-  viously noted was dislodged f rom the side of the finger bowl. The snail extended its foot and attached itself to the dorsal thoracic region of the beetle. It then proceeded to crawl the length of the beetle larva before falling off the animalT s posterior. Following the above events, the Tropisternus was  noted to be i n  dis t ress .  I ts  body was coated by mucus wherever the snail 's  foot had made contact, and i t s  legs  were  inextricably bound together by viscous s t rands  of mucus. The unfortunate l a rva  began violent contractions of the body, while attempting to keep the anal spiracle to the water ' s  sur-  face. When i t s  legs  came in  contact with the surface film, a i r  bubbles attached to the mucous coating on them. The bubbles subsequently buoyed the venter, leaving the larva in  a state of imbalance. The in- sect  continued i t s  contortions, became separated f rom the surface film, and fell to the bottom of the finger bowl. The observer attempted r e s -  cue by moving the larva to the Ceratophyllunz a t  the surface, where i t  continued twisting and contracting the anterior portion of i t s  body while still attempting to separate i t s  legs. After a time it became motion- l e s s  and dropped the fly larva. It resumed the twisting and contorting and again fell to the bottom of the finger bowl. I t s  contortions contin- ued, with periodic lapses,  but surface fi lm contact was  never regained. Finally the Tropisternus died f rom suffocation. 1Willson: Interference of the Snail Physa Sayii with Equilibrium in TropistPublished by ValpoScholar, 1966

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Interference of the Snail Physa Sayii with Equilibrium in Tropisternus Glaber (Coleoptera: Hydrophilidae)

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