2494 M Motile References collected extensively from Russia, including Sibe- ria and Russia’s (at the time) possessions of Alaska Barlow HS (1982) An introduction to the moths of South and . As a colonel in the military, he had East Asia. Malayan Naturalist Society, Kuala Lumpur, unusual access to travel, and took full advantage of Malaysia, 305 pp, 50 pl his journeys, collecting and studying Coleoptera in Common IFB (1990) Moths of Australia. Melbourne Univer- sity Press, Carlton, Australia, 535 pp, 32 pl Europe, North Africa, and much of Covell CV Jr, (1984) A field guide to the moths of eastern in addition to the locations previously mentioned. North America. Houghton Mifflin, Boston, MA, 496 pp, Indeed, it is sometimes stated that his collecting 64 pl trips were a cover for military intelligence. He also Dominick RB, Hodges RW, Dominick T, Edwards CR, Hodges ER (eds) (1971) – The moths of America north of Mex- processed enormous amounts of material collected ico, including Greenland. Wedge Entomological Foun- by others. Motschulsky was a strong-illed, inde- dation, Washington, DC, 27 fasc pendent, and controversial individual. He was pos- Hering EM (1951) Biology of the leaf miners. W. Junk, The sessive, superficial with his descriptions, rough on Hague, The Netherlands, 420 pp, 2 pl Holloway JD, Kibby G, Peggie D (2001) The families of Male- specimens, and unconventional with his mounting sian moths and butterflies. E. J. Brill, Leiden, The Neth- techniques. This led him to clash with other coleop- erlands, 455 pp, 8 pl terists of the time, particularly Kraatz. He died June Inoue H, Sugi S, Kuroko H, Moriuti S, Kawabe A (1982) Moths of Japan. Kodansha, Tokyo, Japan, 2 vol, 392 pl 5, 1871, at Simferopol, Crimea, Russia. Krenek V (2000) Small moths of Europe. Cesky Tesín, Czech Rep, 174 pp Pinhey EGC (1975) Moths of Southern Africa. Tafelberg, References Capetown, South Africa, 273 pp, 63 pl Robinson GS, Tuck KR, Shaffer M (1994) A field guide to the smaller moths of south-east Asia. Malaysian Naturalist Essig EO (1931) A history of entomology. The Macmillan Society, Kuala Lumpur, Malaysia, 309 pp, 32 pl Company, New York, 1029 pp Watson A, Whalley PES (1975) The dictionary of butterflies Herman LH (2001) Motschulsky, Victor Ivanovich. Bull Am and moths in color. McGraw Hill, New York, NY, 296 pp, Mus Nat Hist 265:110–112 144 pl Young M (1997) The natural history of moths. T. & A.D. ­Poyser, London, United Kingdom, 271 pp, 16 pl Mountain Midges Motile Members of the family Deuterophlebiidae (order Diptera). Active. Able to move freely.  Flies

Motor Neurons Mountain Pine , Neurons associated with the central nervous sys- ponderosae tem that transmit information to muscles and (Coleoptera: , glands. Scolytinae)

Barbara Bentz Motschulsky, Victor Ivanovich USDA Forest Service, Logan, UT, USA

Victor Motschulsky was born in 1810 in Russia, The mountain pine beetle, Dendroctonus pondero- and became one of the most famous Russian ento- sae Hopkins, is considered one of the most eco- mologists and greatest coleopterists of his time. He nomically important species in coniferous Mountain Pine Beetle, Dendroctonus ponderosae (Coleoptera: Curculionidae, Scolytinae) M 2495 forests of western North America. Adult other mountain pine beetles on the tree. Aggrega- are capable of successfully reproducing in at least tion pheromones enable mountain pine beetles to 12 North American species of Pinus (Pineacea) overcome the defenses of large, vigorous host trees from southern to northern Baja by rapid and highly concentrated attacks. In this . Mountain pine beetle adults attack live manner, mountain pine beetles are functionally trees, and typically must kill the host for success- able to expand their own food supply. Larger trees ful reproduction. Population outbreaks are most require more adults to overcome the tree resin common in a few selected host species, such as defensives, but also produce a larger number of lodgepole pine (P. contorta), ponderosa pine brood the following generation for continued tree (P. ponderosa), western white pine (P. monticola), attack. Because a single tree is a finite resource, whitebark pine (P. albicaulis), and sugar pine pheromones are also produced which interrupt (P. lambertiana), which often grow in relatively the aggregation of adults on a tree. The interrup- homogeneous groups over large acreages. Moun- tive aggregation pheromones direct incoming tain pine beetles typically attack older lodgepole adults to unoccupied portions of the tree under and whitebark pine (e.g., greater than 80 years), attack, and also to nearby host trees, thereby reduc- while younger ponderosa, western white, and ing competition for resources within a single tree. sugar pine can also be attacked. Trees that are In this manner, during an outbreak, thousands of stressed by factors such as overcrowding, water, trees can be attacked and killed in a single year. and pathogens are especially vulnerable. Once inside a new host tree, adults mate and The lifecycle of the mountain pine beetle is are laid individually on each side of galleries highly dependent upon temperature. Commonly, excavated vertically in the phloem. Phloem is the populations are univoltine, although at higher ele- inner tissue layer just below the outer bark which vations where average temperatures are colder, 2 translocates carbohydrates up and down the tree. and sometimes 3 years are required to complete a Mountain pine beetle larvae feed horizontally in generation. Adult beetles emerge from host trees the phloem, cutting off nutrient translocation, and disperse to new hosts in the warm summer thereby killing the host tree. Larval development months when temperatures are above 15.5°C. rate, which is highly dependent on temperature, Although timing of emergence will vary from dictates the life stages present during the winter. year to year depending on beetle development Available evidence indicates that the mountain and temperature, peak adult emergence typically pine beetle does not diapause, and all larval life occurs within a 2–3 week time span. Rapid and stages may be found overwintering under the bark synchronous emergence of the population is of host trees. The larvae, which are intolerant of essential for mountain pine beetle success in over- freezing temperatures, survive low temperatures coming the resinous defenses of healthy host trees. by supercooling. Populations in Idaho have been Adult dispersal involves movement within an found to survive temperatures as low as −35°C. infested patch of trees, movement between infested Mortality due to cold temperatures is usually patches of trees, and movement out of the imme- greatest during the spring and fall months when diate area for initiation of new patches. Long range larvae may not be appropriately acclimated to dra- dispersal to new areas is often aided by wind cur- matic swings in temperature. Woodpeckers, clerid rents, whereas local dispersal is directed by aggre- beetles (Enoclerus spp., Thanasimus spp.), and par- gation pheromones, compounds released when asitic wasps are also the cause of a small amount of adult beetles attack and feed on new host trees. mountain pine beetle mortality, mostly at endemic Monoterpenes, which are major constituents of population levels. pine resin, are converted by adult beetles to com- Pupation occurs in the early summer followed pounds which, when released, act to aggregate by a teneral adult stage during which the new 2496 M Mountain Pine Beetle, Dendroctonus ponderosae (Coleoptera: Curculionidae, Scolytinae) adults feed on a diverse flora of microbial symbi- growth. A mosaic of vegetation types across a onts including fungi (Ophiostoma spp.) and yeasts landscape, partitioned by age and host and non- found within the pupal chamber. During this feed- host species, may also help to reduce large scale, ing period, the microorganisms are acquired in widespread mortality. the mycangia, a specialized structure of the integ- Options for management of mountain pine ument. When the adult beetle emerges from the beetle populations depend on the specific land use host tree for dispersal to a new tree, the fungi and objectives. Forested areas targeted for timber pro- yeasts are carried inside the mycangia and inocu- duction can be silviculturally treated to facilitate lated into the phloem of the new host. Although reduced susceptibility to mountain pine beetle the role of Ophiostoma spp. in mountain pine outbreaks. Many areas designated as wilderness, ­beetle population dynamics are not fully under- however, are managed as natural areas and timber stood, at least one species appears to be beneficial harvest is not a major objective. Within these areas to population success, while detrimental effects the historical role of the mountain pine beetle in are attributed to another species. Following matu- forest ecosystems may be emphasized. Mountain ration feeding in the teneral adult stage, new adults pine beetle populations, which are native to western emerge from the dead trees to disperse, attack new North America, have evolved with their pine hosts live host trees, and begin the cycle again. and are significant components of healthy, func- Given appropriate weather and stand condi- tioning ecosystems. In particular, the mountain tions, populations of mountain pine beetles are pine beetle and fire are considered important dis- capable of attacking and killing hundreds of thou- turbance agents favoring the regeneration of lodge- sands of trees in a few years. This magnitude of pole pine. While tree death is a difficult concept for mortality can disrupt forest management plans, humans, it is a normal step in the rejuvenation and recreation, watershed, wildlife, and timber pro- succession of forest ecosystems, and the mountain duction. In areas of high value, such as forest pine beetle is an important part of this process. campgrounds and ski areas, direct control tactics  Bark Beetles in the Genus Dendroctonus such as insecticides are often used to temporarily reduce mountain pine beetle caused mortality. Synthetic forms of the aggregation pheromone References may also be used to concentrate adults in traps or trees which are then removed from the area. Ongo- Amman GD, Cole WE (1983) Mountain pine beetle dynamics ing research is aimed at understanding the role of in lodgepole pine forests Part II: Population Dynamics. USDA Forest Service, Intermountain Forest and Range interruptive aggregation pheromones in mountain Experiment Station, General Technical Report INT-145 pine beetle population dynamics, in the hope that Borden JH, Chong LJ, Lindgren BS (1990) Redundancy in the synthetic forms of these compounds may also pro- semiochemical message required to induce attack on vide a tool for direct population control. While lodgepole pines by the mountain pine beetle Dendrocto- nus ponderosae Hopkins (Coleoptera: Scolytidae). Can direct control tactics are useful in small, high value Entom 122:769–777 areas, they are not effective or feasible over large Logan JA, Bentz BJ (1999) Model analysis of mountain pine areas, and do not alter the habitat and stand condi- beetle (Coleoptera: Scolytidae) seasonality. Environ tions that are favorable to mountain pine beetle Entomol 28:924–934 McGregor MD, Amman GD, Schmitz RF, Oakes RD (1987) populations. The optimum approach in areas Partial cutting lodgepole pine stands to reduce losses to which have been targeted for management is pre- the mountain pine beetle. Can J For Resour vention. Silvicultural practices such as thinning, 17:1234–1239 Raffa KF (1988) The mountain pine beetle in western North which decrease the density of host trees, help to America. In: Berryman AA (ed) Dynamics of forest maintain vigorous trees and create a less favorable insect populations, patterns, causes and implications. habitat for mountain pine beetle population Plenum Press, New York, NY, pp 506–531 Mouthparts of Hexapods M 2497 Shore TL, Safranyik L (1992) Susceptibility and risk rating characteristic of the hexapods. Therefore, the systems for the mountain pine beetle in lodgepole pine division of the mandibles into mono- and dicon- stands. Forestry Canada, Pacific Forestry Centre, Victoria, Canada dylic is not fitting (Koch 2001); because of this, and owing to the great variability existing in the hexapods, this author prefers to treat separately the mandibles of each one of the large groups: Mouth Beard Collembola, Protura, Diplura, Archaeognatha, Thysanura and Pterygota. In robber flies (Asilidae), the prominent tuft of Despite the opinion of Koch, many authors hairs at the front of the head. This is also called consider, at least from a practical point of view, the the mystax. type and number of articulations within the head capsule to separate two fundamental types of mandibles: monocondylic (one articulation) and Mouth Cone dicondylic (two articulations). The monocondylic type is characteristic of the majority of Apterygota, A term used to describe the mouthparts arrange- although in Collembola, Protura and Diplura an ment of thrips (Thysanoptera). authentic mandibular condyle does not exist as in  Mouthparts of Hexapods the case of Archaeognatha. This monocondylic type appears secondarily in entognathous Ptery- gota, with mouthparts transformed into stylets. Mouth Hooks The dicondylic type is typical of the Pterygota, where two mandibular articulations are differenti- In larvae of the higher Diptera, the mandible-like ated, one in the anterior position and another pos- feeding structures located at the oral cavity. terior. An intermediate condition exists between the mono- and dicondylic types. In it the mandi- bles, in addition to the principal articulation (cor- Mouthparts of Hexapods responding to the only condyle of Archaeognatha), present a secondary articulation known as the Severiano F. Gayubo epicondyle. It is situated in the anterior third of Universidad de Salamanca, Salamanca, Spain the mandibular body and therefore differs from the second articulation of Pterygota, which has The hexapods are trignathan, that is to say they a clearly posterior position. This intermediate present three pairs of buccal appendages, each one model is displayed in Thysanura and nymphs of of them situated in the corresponding cephalic Ephemeroptera. segment: a pair of mandibles (mandibular seg- The morphology of the mandible varies ment), a first pair of maxillae (maxillary segment), according to the diet and is usually characteristic and a second pair of maxillae that fused, form the in each of the hexapod orders. Nevertheless, it labium (labial segment). basically consists of an incisor zone in the distal Recently, certain authors affirm that the clas- or subdistal position and another molar zone sit- sic point of view, according to which the true uated on the internal mandibular face. The greater capacity of “biting” by the Dicondylia [Thysanura or lesser development of these two zones is found (Zygentoma) plus Pterygota] is functionally cor- in the function of the alimentary behavior. Thus, related to the acquisition of dicondylic mandi- in predatory species the incisory zone is usually bles, cannot be maintained, taking into account well developed, since it serves to cut and tear the that the capacity of “biting” transversely is a trait prey. On the contrary, in phytophagous species