CHAPTER 5 



Aquatic Orthoptera 



By Iro La Rivers 

 University of Nevada, Reno 





Grasshoppers and crickets are not usually thought 

 of as aquatic animals; however, one group is inti- 

 mately associated with water — the Tridactylidae or 

 pygmy molecrickets. These peculiar and unfamiliar 

 little insects are fossorial, burrowing in the loose, 

 saturated sand bordering water, and are able to swim 

 by means of specially modified natatory lamellae 

 ("calcaria") or swimming plates borne on the ends 

 of the hind tibiae. However, the ability of these 

 animals to handle themselves competently about 

 water does not require such remarkable adaptations, 

 since most saltatorial Orthoptera are so constructed 

 that locomotion through water comes rather naturally. 

 In contrast to most strictly terrestrial insects, even 

 the desert grasshoppers swim readily and strike out 

 efficiently for shore when they accidentally fall 

 into water. 



The grouse or pygmy locusts (Acrydiidae), in parti- 

 cular, exhibit a proficiency about water though lacking 

 such definite structural modifications as the tridacty- 

 lid natatory lamellae, and may dive beneath the 

 surface of the water when disturbed. Grouse locusts 

 are not treated here because they are primarily terres- 

 trial or certainly no more than semiaquatic. 



Little has been published on the biology of tri- 

 dactylids. Within the past thirty years, only a few 

 authors have made even passing mention of the aquatic 



<^ 



Fig. 5:1. Adult male of the pygmy molecricket, Tridoctylus 

 minutus Scudder (courtesy Illinois Natural History Survey.) 



associations of our species. Blatchley (1920) men- 

 tions their swimming plates or "calcaria," and notes 

 that they burrow in moist sand and can leap about or 

 the surface of the water. Hebard's extensive 193^ 

 treatment of the Orthoptera and Dermaptera of Illinois 

 suggests only that they occur "about lakes and water- 

 courses"; Urquhart (1937) takes some notice of them; 

 and Chopard (1938), repeating Urquhart's observations 

 in a more comprehensive survey, has something tc 

 say about their habitat (p. 84), their hibernatior 

 (p. 260), and their family associations (p. 506). 



Family TRIDACTYLIDAE 



Genus Tridactylus Olivier 1789 

 (Ellipes Scudder 1902) 



Key to California Species (from Hebard 1934) 



1. Hind tarsus present, 1-segmented; pronotum with i 

 weak transverse furrow; shining brown in color, little 

 or not at all maculate; Santa Ana R., near Ontario 



Riverside Co.. Calif apicalis Say 182 J 



— Hind tarsus entirely absent; pronotum lacking furrow; 

 blackish-brown in color, usually strikingly maculate 

 with a buffy color; Calaveras, Humboldt, Los Angeles 



Monterey, Riverside, San Diego counties 



minutus Scudder 186! 



REFERENCES 



BLATCHLEY, WILLIS LINN 



1920. The Orthoptera of Northeastern America. Indian 

 apolis: Nature Publ. Co., 784 pp. 

 CHOPARD, L. 



1938. La Biologie des Orthopteres. Encycl. Entom. 

 20:1-541, 4 pis. 

 HEBARD, MORGAN 



1934. The Dermaptera and Orthoptera of Illinois. Illinois 

 Nat. Hist. Surv. Bull., 20:125-279. 

 URQUHART, F. A. 



1937. Some notes on the sand cricket {Tridactylui 

 apicalis Say). Canad. Field Nat., 51:28. 



154 



