The Embioptera of California
Total Page：16
File Type：pdf, Size：1020Kb
Chelicercu rubru (Ross), male. The only known endemic species of Embioptera ~ccurring in California. KOH-cleared microscope slide preparation. Body length 6.5 mm. BULLETIN OF THE CALIFORNIA INSECT SURVEY VOLUME 6, NO. 3 THE EMBIOPTERA OF CALIFORNIA BY EDWARD S. ROSS (California Academy of Sciences) UNIVERSITY OF CALIFORNIA PRESS BERKELEY AND LOS ANGELES 1957 BULLETIN OF THE CALIFORNIA INSECT SURVEY Editors: E. G. Linsley, S. B. Freeborn, P. D. Hurd, R. L. Usinger Volume 6, No. 3 pp. 51-58, frontis., 7 figures in text Submitted by Editors, November 11, 1956 Issued September 3, 1957 Price, 50 cents UNIVERSITY OF CALIFORNIA PRESS BERKELEY AND LOS ANGELES CALIFORNIA CAMBRIDGE UNIVERSITY PRESS LONDON, ENGLAND Printed by Offset in the United States of America THE EMBIOPTERA OF CALIFORNIA by EDWARD S. ROSS INTRODUCTION greatly swollen, gland-packed foretarsi. Both sexes Embioptera are essentially tropical insects and, and all developmental stages, even including the as in most other temperate regions, are very poor- first instar, spin silk. The basal segment of the ly represented in California. To date only three three-segmented foretarsus contains scores of silk species have been found in the state, and it is glands. Each gland consists of a round lumen de- unlikely that this number will increase except by limited by a layer of syncytial, silk-producing the unintentional introduction of additional species cells. The silk, still in a viscid state, is conduct- by man. ed from the lumen of each gland through a long Such introductions are quite possible because duct which opens to the exterior at the apex of a of the ease with which embiids travelin commerce hollow spinning seta on the plantar surfaces of in the shock-proof protection of their quickly estab- the basal and medial tarsal segments. Many fine lished silken galleries. Embiids are commonly in- strands of silk are simultaneously spun with each tercepted in plant quarantine, especially in ship- stroke of the tarsus. ments of orchid plants from the tropics. The fact With these remarkable organs, embiids can that potential immigrants can occasionally slip rapidly construct highly protective silk tunnels through our borders was demonstrated by the col- wherever they go in search of food or in escape lection by Dr. W. H. Lange of a live adult male of from adverse ecological conditions. The eggs are the pan-tropical species, Oligotoma saundersii laid in a protected place in the tunnel system, and (Westwood), on Hawaiian pineapples in a store in the gregarious, newly hatched young spin their Berkeley, California, July, 1340. Eventually this own tunnel system which increases both in extent species may become established (as it already is and tunnel diameter as the insects grow. In Cali- in Florida and Texas) in southern California, but fornia, and other regions which experience pro- no economic problems should arise as a result. longed dry seasons, these tunnel systems are gen- The most common of the three California spe- erally spun under the protective cover of a stone, cies are two well-established Old World members log, dry cattle dropping, or matted leaves. The of the family Oligotomidae which were early intro- tunnels, which give evidence of the presence of duced in commerce. One of these is a partheno- Embioptera at any season, generally follow soil genetic form of the Mediterranean Haploembia soli- cracks to depths where the insects retreat during eti (Rambur); the other is Oligotom nigra Hagen, the heat of the day or long hot dry periods. a species common in the Nile Valley and Middle Most of the anatomical and biological charac- East. teristics of embiids are adaptations to a life large- The third California species, Chelicerca rubra ly confined to silk tunnels. These are: (1) an elon- (Ross), is rarely seen by collectors. Its occurrence gate, supple body form with short legs and a high in the state is natural, but its taxonomic affinity degree of prognathism; (2) an ability to run back- is with a group (subgenus) of northwestern Mexican ward aided by highly developed hind tibial depres- species as yet undescribed. sor muscles; (3) highly sensitive cerci to guide the backward movement; (4) universal apterism of GENERAL BIONOMICS the female through neoteny and a similar tendency (partial or complete) in males of many species; The most singular feature of all Embioptera is an (5) development of wing flexibility in the male (an ability to produce sheet-silk by quick strokes of advantage during reverse movement in tunnels) and 52 BULLETIN OF THE CALIFORNIA INSECT SURVEY a compensating wing stiffening for flight by blood California, Los Angeles; U.C.R., University of pressure, principally in the wing’s first radius California, Riverside. vein. Except for such specializations, Embioptera are rather generalized orthopteroid insects with a Key to California Species of simple life history and unspecialized food habits. Embioptera (any instar) The diet is usually dead leaves, grass, bark flakes, lichens, and moss. At times Embioptera will nibble 1. Hind basitarsus with a medial, membranous living plant tissue, especially grass at the edge sole-bladder in addition to the usual terminal of a stone. Wherever embiids choose tolive on the terminal bladder (fig. 2). Parthenogenetic basis of other ecological factors, there is almost species . Haploembia solieri (Rambur) certain to be a supply of food. Species represent- Hind basitarsus without a medial sole-bladder ing highly divergent taxonomic groups from very (fig. Bisexual species 2 distinct regions and ecological niches readily ac 1). cept the same diet in laboratory cultures. 2. Small species (adults less than 8.0 mm. in Although the silken tunnels must be highly length). Juveniles pale reddish-brown; adult efficient protection from predators, especially by female brick-red; adult male red with terminalia providing prearranged escape routes, embiids must and head black. Left cercus of male one-seg- regularly fall prey to beetles, spiders, ants, and mented, long arcuate (fig. 3). the like. In regions of endemicity each species is . Chelicerca rubra (Ross) also attacked by specific parasites. The eggs are Larger species (adults at least 9.0 mm. in parasitized by tiny wasps of the family Scelionidae, length. Juveniles pale tan; adult female black- and the embiid bodies are attacked by ectophagous ish-brown; adult male uniformly medium to dark wasp larvae of the bethyloid family Sclerogibbidae brown. Left cercus of male two-segmented, and larvae of midges of the family Itonidae. Other segments straight (fig. 4) . kinds of specific parasites and predators thrive . Oligotoma nigra Hagen on embiids in certain regions. New taxonomic cate- gories will be added to the California insect list when the parasites of the endemic Chelicera rubra Family Anisembiidae are reared. The two nonendemic species probably Genus Chelicerca Ross owe much of their biological success to freedom from attacks of their specific parasites. Chelicerca (Dactylocerca) rubra (Ross) None of the Embioptera of California-in fact (Frontis.; fig. 3) of any region of the world-can be classed as eco- nomic pests. It is possible, however, that a pest Anisembia (Dactylocerca) rubra Ross, Ann. Ent. control operator may at times be called to answer Soc. Amer., 332559. Type locality: Rosarito inquiries concerning Embioptera colonies about Beach, Baja California, C.A.S. the house or garden, but the chances of real horti- cultural or household damage is practically nil be- Geographic range: cause of vegetable-scavenger food habits of the Aripna, Baja California, Sonora (probable), insects. Mexico; California, New Mexico, and Utah. California records: Kern Co.: 5 mi. w. Tehachapi, colonies under Acknowledgments stones mixed with those of Haploembia solieti (Rambur), males mature VI-49 (E. S. Ross, C.A.S.); I am indebted to the various collectors and museum Randsburg, late instar juveniles, IV-6-48 (J. W. officials cited in the accompanying records for MacSwain, C.I.S.). their contributions and assistance. The collections Riverside Co.: Banning, penult. male under referred to by symbol are: C.A.S., California Acad- stone in desert (D. W. Pierce, L.A.M.); Palm Can- emy of Sciences, San Francisco; C.I.S., California yon, male in flight, IV-16-37 (G. E. and R. M. Bo- Insect Survey, University of California, Berkeley; hart, C.A.S.); Palm Canyon, colonies under stones C.D. A, California State Department of Agricul- and skirts of fan palms, IV-15-39 (E. S. Ross, C. ture, Sacramento; C.U., Cornel1 University, Ithaca, A.S.); Pigon Flat, San Jacinto Mts., 2 males in N.Y.; L.A.M., Los AngeIes County Museum; K.U., sweepings, V-24 and 27-39 (E. G. Linsley and University of Kansas, Lawrence; U.C.D., Univer- J. G. Shanefelt, C.A.S.); same locality, colonies sity of California, Davis; U.C.L.A., University of under stones, IV-8-54(E. S. Ross, C.A.S.). THE EMBIOPTERA OF CALIFORNIA 53 4 Figs. 1-4. Key characters of California Embioptera: Fig. 1. Hind tarsus adult female Oligororncr nigra Hageo, showing single (apical) sole-bladder. Fig. 2. Hind tarsus of Naploembia solieri (Ramhur), showing two basitarsal sole-bladders. Fig. 3. Cheli- cerca rubra (Ross), abdominal terminalia of male. Fig. 4. Oligotomn nigra Hagen, abdominal terminalia of male. Explanation of symbols: 9 = ninth abdominal tergite; 10 L and 10 R = left and right hemitergites of tenth segment; 10 Lp and 10 RP = processes of 10 L and 10 R; MF = median flap of 10 R; EP = epiproct; HP = hypandrium process; LPPT= left paraproct; LCB = left cercus-basipodite: LC1+2 = composite two-segmented left cercus. Terminalia figures omit setae except micro-setae or echioulations of LC1+2. Stippling represents membrane. 54 BULLETIN OF THE CALIFORNIA INSECT SURVEY San Diego Co.: Borrego State Park, juveniles, in the San Pedro Martir Mountains, Baja California, IV-25-55 (R.O.