Charles S. Henry.
Some Aspects of the External Morphology of Larval Owlflies (Neuroptera: Ascalaphidae), with Particular Reference to Ululodes and Ascalopterynx.
Psyche 83:1-31, 1976.

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PSYCHE
Vol. 83 March, 1976 No. 1
SOME ASPECTS OF THE EXTERNAL MORPHOLOGY OF LARVAL OWLFLIES (NEUROPTERA: ASCALAPHIDAE), WITH PARTICULAR REFERENCE TO
ULULODES AND ASCALOPTYNX
The Biological Sciences Group, University of Connecticut Storrs, Connecticut 06268
It is widely known and accepted among evolutionary biologists that the selective pressures upon the immature stages of an organism may be very different from those upon the adult form. This principle is especially true of the endopterygote (holometabolous) insects: in these, there can be seen a nearly complete dissociation of the larva from the adult, manifested both biologically and morpho- logically. Thus it often happens that phylogenies based upon fea- tures of the immature endopterygote insect differ sharply from those constructed from the adult; ideally, both kinds of information should be available to and utilized by the taxonomist. The Neuroptera** is thought to be the most generalized and primitive endopterygote order, and as such is considered to include forms that are closest to the common ancestor of all Endopterygota. Such families as Sialidae, Corydalidae and Raphidiidae express their primitive phylogenic positions by the relatively small degree of biological and morphological divergence exhibited between larva and adult. Other families and complexes of families within the Neuroptera, notably the superfamily Myrmeleontoidea (ant lions and their relatives), are highly specialized, possessing larval forms that in no way resemble the adults. The larvae of most myr- *Parts of this paper are adapted from a thesis submitted to the Department of Biolo- gy at Harvard University in partial fulfillment of the requirements of thePhDdegree. **This term is used in the wide sense, including suborders Megaloptera, Raphidio- dea and Planipennia.
Manuscript received by the editor April 15, 1976.



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meleontoid insects are cryptic in habits and coloration and often difficult to rear to adulthood. For these reasons, few have been reliably associated with adult forms, so taxonomic and phylogenetic studies have necessarily been based primarily upon the morphology of preserved images. In the myrmeleontoid family Ascalaphidae, larval-adult associations have been achieved for only five or possibly six of 65 described genera (MacLeod, 1970). Addition- ally, all of these published associations are within one of the two ascalaphid subfamilies, the Ascalaphinae; no neuroptyngine (=ascaloptyngine) larva has been formally described. despite the fact that nearly one third of ascalaphid genera are contained in the latter subfamily (Weele. 1908).
Only a few authors have made serious attempts to bring biological information about the immatures to bear upon the problems of phylogeny within the Neuroptera in general and Ascalap hidae in particular. The first of these was Hagen (1873), who described six- teen larval "types" within the Ascalaphidae and correctly assessed the taxonomic importance of numerous larval characters, but failed to establish strong evidence for larval-adult relationship in most cases. Navas (1914, 191 5), like Hagen, stressed the importance of such larval features as the number and distribution of lateral ab- dominal scoli (extensions), particularly in separating the split-eyed (Ascalaphinae) from the entire-eyed (Neuroptynginae) ascalaphid subfamilies. However, his papers are crudely illustrated and suffer from the same (if not more) uncertainty of larval identity as do Hagen's; it is by no means certain or even likely that his assignment of several larvae to the subfamily Neuroptynginae is correct. Withy- combe's work (1925) is far more ambitious, important, and accurate, assembling a large body of behavioral, physiological and morpho- logical data on immature Neuroptera. Since he was not seeking evolutionary relationships within families like the Ascalaphidae but rather among all neuropteran families, Withycombe did not usually require or attempt species-level identifications. Finally, MacLeod (1 964) produced a thorough, well-reasoned and superbly illustrated work on Neuroptera of a scope similar to that of Withy- combe's but emphasizing comparative morphology of the larval head capsule rather than behavior and physiology. This is the first work to figure in detail the head capsule of an ascalaphid larva of the genus UZuZodes [ U. quadrimaculata (Say)] and to document, by rear- an adult association of a neuroptyngine ascalaphid larva [Ascalop- tynx appendiculatus (Fabricius)]. Unfortunately, MacLeod's excel-



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lent study remains unpublished, with only small parts appearing in abbreviated form in his 1970 paper on fossil neuropteran larvae. A significantly larger number of authors have concerned them- selves with evaluating the evolutionary relationships within and among neuropteran families through analysis of adult morphology and wing venation. The most important works of this type include the broad-based studies of Tillyard (1 91 6, l926), Adams (1958) and Shepard (1967) and the ascalaphid monographs of McLachlan (187 l), Week (1908), Navas (1913) and Orfila (1949). Papers of more limited scope on the immatures of particular ascalaphid spe- cies will be discussed in the concluding section of this study. It is my intention eventually to re-assess the evolutionary pat- terns within the family Ascalaphidae, based upon morphological, behavioral, and life-cycle information pertaining to the immature stages of as many species as possible. Work toward this end was initiated in a comparative study of eggs, egg barriers (repagula) and early larval habits of two North American owlflies, Ululodes mexicana (McLachlan) and Ascaloptynx furciger (McLachlan), representing both ascalaphid subfamilies (Henry, 1972). The pur- poses of the present paper are (a) to provide formal generic and specific descriptions of the larvae of the above-named species, (b) to summarize key morphological differences between them and among other described forms, and (c) to suggest a tentative list of evolutionarily significant larval characters defining the as- calaphid subfamilies. The description of Ascaloptynx furciger is particuarly useful as the first, to my knowledge, published descrip- tion of a neuroptyngine (entire-eyed) owlfly larva. Papers on the behavior and life history of Ululodes mexicana and Ascaloptynx furciger are in preparation. Much of the larval material assembled for this study was collected while I was a graduate student at Harvard University, Cambridge, Massachusetts. Collecting trips were financed by a three-year National Science Foundation Pre-Doctoral Fellowship, a Harvard University Richmond Fellowship, and grants from the Committee on Evolutionary Biology (NSF Grant GB 2791 1, Reed Rollins, Harvard University, Principal Investigator). Later trips to examine material in European museums and to collect living ascalaphid larvae from Europe were arranged through an NSF Institutional Grant at The George Washington University, Washington, D.C.



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Living and preserved specimens were lent or given to me by Drs. Robert E. Silberglied and Thomas Hlavac (Museum of Com- parative Zoology), M. A. Kolner and F. F. Hasbrouck (Arizona State University, Tempe), and James A. Slater (University of Con- necticut); to these individuals I express great appreciation. In addition, warm thanks are extended to: Nancy F. Henry, for in- valuable collecting assistance in the field and moral support at home; Mr. Vincent Roth of the Southwestern Research Station, for his advice on my field work in Arizona; M. Professeur A. Haget (Universitk de Bordeaux) for helpful suggestions pertaining to my collecting trips in France; and Drs. C. W. Rettenmeyer, C. W. Schaefer, and J. A. Slater (University of Connecticut) for their constructive comments on the manuscript. Special thanks are extended to my colleague, friend and former advisor Professor Frank M. Carpenter, who has been consistently encouraging and helpful to me in my work on the Neuroptera. METHODS AND MATERIALS
Ascalaphid larvae are extremely difficult to find in the field, even with intensive litter-sifting efforts. For this reason, field-laid eggs of the two owlfly species were collected, using techniques outlined in a previous paper (Henry, 1972). Eggs of Ascaloptynx furciger and Ululodes mexicana were found in abundance during August and September in the Chiricahua and Peloncillo Mountains, within a 25 mile radius of the Southwestern Research Station of the Amer- ican Museum of Natural History (S WRS) in southeastern Arizona. Elevations of egg sites ranged from 1500 to 1800 meters (see Henry, 1972). Larvae hatching from these egg masses were maintained in 15 x 60 mm plastic petri dishes, one insect per dish, on a substrate of sterile sand (U. mexicana) or dried leaves of oaks native to Ari- zona egg sites (A. furciger). Each isolated larva received a letter and number designation and its movements, molts, etc., were re- corded in chart form. Some dishes with larvae were kept in a one cubic foot wooden cabinet with regulated photoperiod but unregu- lated temperature regimen; others occupied a constant temperature and photoperiod Precision Scientific/GE Model 805 incubator. Temperature in the first chamber ranged from 30å¡ in the "day" to 22' C at "night;" the incubator was set for a constant 29O C. Light period was normally maintained at LD (lightldark) 16:8 hours.



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19761 Henry-hrval Owlflies 5
Newly hatched larvae of both species were fed single live Dro- sophila melanogaster (Meigen) and D. hydei (Sturtevant) daily for the first week. They were later fed twice a week with first and second instar nymphs of Blattella germanica (Linn.). Each late third (last) instar ascalaphid was fed an adult female B. germanica roach once a week.
Larvae in various stages of development were killed in and ini- tially fixed and injected with Bouin's solution. After 12 to 24 hours, specimens were transferred to 70 percent ethanol or, for mild clear- ing of sclerotized structures, to Weaver's dissection and preserva- tion fluid: 2 parts 40% formalin, 1 part glacial acetic acid, 8 parts chloral hydrate, and 29 parts distilled water. When greater clearing was required, warm 10 percent potassium hydroxide or Nesbitt's solution (Nesbitt, 1945) proved adequate. Very small specimens and structures were run through dehydrating solutions of alcohol and xylene and mounted in Damar on depression slides. Observa- tion, dissection and figuring of specimens involved use of a Wild M5 stereoscopic dissecting microscope equipped with integral camera lucida, and various Bausch and Lomb compound micro- scopes fitted with 10
10 micrometer eye-piece grids.
Most of the methods outlined above apply equally well to the collection, rearing, preservation and observation of other ascala- phid immatures used incidentally in this study, including an un- identified species of Ululodes from central Florida and Ascalaphus libelluloides (Schaffer) from south-central France. Large numbers of viable eggs of the latter European species were found on low herbiage clothing rugged hillsides near the Aveyron River outside the village of Penne, in the French district of Tarn-et-Garonne. The characteristics that define larvae of the extant Ascalaphidae and that set this family apart from other myrmeleontoid taxa like Psychopsidae, Nymphidae, Myrmeleontidae, Nemopteridae and Stilbopterygidae* have been discussed at length in the works of Withycombe (1925) and MacLeod (1964, 1970). These include (a) posterior margin of the head capsule strongly cordate, (b) pres- *Larvae of this peculiar Australian and South American family are not suffi- ciently known to permit confident comparisons; immatures of Psychopsidae, Nymphidae and Nemopteridae are also poorly known.



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ence of three true teeth on each mandible, (c) presence of seven lateral stemmata, one ventral and six dorsal, on each distinctly raised ocular tubercle, (d) lack of any pronounced prolongations of other specializations of the cervix, (e) presence of ten to nineteen pairs of finger-like or spatulate setose extensions called scoli, later- ally fringing the thorax and abdomen, (f) ventral or lateral location of the spiracles of abdominal segments 3-8 and occasionally of all eight pairs of abdominal spiracles, and (g) fusion of the tibia and tarsus on each metathoracic leg. None of these features uniquely characterizes ascalaphid larvae to the exclusion of other myr- meleontoid families. For example, seven pairs of stemmata is typical of all Myrmeleontoidea except Psychopsidae (5) and possibly Nymphidae (6 in the larva of Nymphes sp.), while scoli are totally absent only in psychopsids and nemopterids. Additional charac- teristic ascalaphid features are shared with one to several other myrmeleontoid families: metathoracic tibio-tarsal fusion with all Myrmeleontidae and probably Stilbopterygidae (McFarland, 1968); simple cervical morphology with most nymphids, psychop- sids and stilbopterygids; three mandibular teeth and raised ocular tubercles with many Myrmeleontidae and perhaps all Stilboptery- gidae; and cordate head margin and spiracle pattern with a few nymphids. However, only owlflies display all of the above char- acter states together in an unmistakable gestalt. Ascalaphid larvae share with all other Myrmeleontoidea (a) a heavily sclerotized, roughly quadrate head capsule displaying a unique anteriorly-positioned, vertically oriented tentorium linking one pair of pits ("anterior" ones) on the dorsum with another pair of pits ("posterior" ones) on the venter (see figures 3 and 6, TAP and TPP); (b) robust, inwardly curved jaws with mandibular- maxillary sucking specializations typical of all planipennian Neu- roptera; (c) relatively small, multisegmented, filiform antennae, each with enlarged scape and inconspicuous pedicel, usually orig- inating from a small antenna1 tubercle; (d) labium distally divided into two large palpimere-like prelabia, each bearing a short, usually 3-segmented* palp (figures 3B and 6B, Plb, Prlb and Pip); (e) stout, ovoid body with varying tendencies toward dorso-ventral flatten- ing, consisting of a thorax and 9-segmented abdomen bearing at *2-segmented in some Nemopteridae and 4-segmented in Psychopsis elegans, according to MacLeod (1964).




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Henry- Larval Owlflies
Figure 1. Ululodes mexicana, mature third instar larva. ScMs mesothoracic scolus, ScMt = metathoracic scolus, Scvg = vestigial mesothoracic scolus, SpMs = mesothoracic spiracle.




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its tip a retractile, tubular tenth segment that functions as a spin- neret; (f) short, powerful walking legs; and (g) dolichasterine (trumpet-shaped) setae of diverse morphology over part or most of the body surface (figure 8). Like most Planipennia, ascalaphid larvae pass through three instars prior to pupation. LARVA OF ULULODES MEXICANA (McLachlan)
(Refer to figures 1-4)
GENERIC DESCRIPTION: Ululodes Currie.
The following description is based upon examination of nearly 100 third instar specimens of UZuZodes mexicana reared from egg to adulthood, together with 13 reared larvae of an unidentified species of UZuZodes from Florida and two preserved third instar specimens representing a third unidentified species of the genus from Pima, Arizona. The generic diagnosis is also based on in- formation presented in two excellent works: first, that of MacLeod (1964), describing the morphology of the head capsule and cervix of Ululodes quadrimaculata (Say) from Illinois, and secondly, that of McClendon (1902), describing the third instar larva of Ululodes senex Burmeister (described as U. hyalina Latreille) from Texas. I have chosen to follow the terminology used by MacLeod (1964, 1970).
Length: just prior to pupation, 13-19 mm, not including jaws. Head: trapezoidal, approximately as wide as or slightly wider than long, broadest posteriorly and tapering evenly anteriorly; dorso-ventrally flattened but much thicker behind than in front. Cordate postero-lateral (occipital) margins. Labral margin (LmM) narrow and very strongly bilobed with a single wide deep notch at midline; labral lobes bulbous. Dorsum flat medially and convex laterally; ventral surface strongly convex with excavated antero- lateral margins permitting retraction of jaws beneath ocular tuber- cles (excv). Surface texture mildly rugose due to slightly raised bases of setae. Ocular tubercles (OT) large, prominent, approx- imately cylindroid but very slightly tapered distally and flattened dorso-ventrally; ventral stemma somewhat reduced in size com- pared with dorsal stemmata. Antenna1 tubercles (AT) prominent, cylindrical, nearly half length of ocular tubercles, appressed closely to bases of latter. Number of flagellomeres variable, usually 11 or 12, with tip of antenna projecting far beyond end of ocular tuber-



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Henry- Larval Owlflies
Figure 2. Ululodes mexicana, immature third instar larva with jaws in "trap" position. Md = mandible.
cle. Jaws falcate, smoothly tapering, and significantly longer than head capsule; they show a strong upward tilt in lateral view and are capable of being opened to an angle of 270 degrees or more (figure 2). First tooth always placed proximad of midpoint of mandible; central tooth much larger than the other two teeth and markedly curved; distal tooth unambiguously the smallest of the three and situated closely adjacent to central tooth. Ventral man- dibular condyle (MdCV) positively contained within robust U- shaped socket formed from anterior ends of subgenal ridge (SgR - see figure 3B), the medial arm of which overgrows and nearly hides maxillary stipes (St). Postlabium (Plb) flask-shaped in outline



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19761 Henry-- Larval Owlflies 11
with very large, crescent-shaped, distally tapered prelabial lobes (Prlb) arising quite close to one another from sides of "neck" of postlabium. Terminal palpimere of labial palpus (Pip) nearly as long as first and second combined.
Body: elliptical in outline and not prominently flattened when mature. Prothoracic .iotum small, sclerotized, convex, roughly elliptical to triangular in outline and nearly twice as broad as long, bearing no scoli or tubercles. Remainder of body lightly sclerotized except for a pair of oval plates situated laterally in tergum of the mesothorax and a second smaller pair similarly located in meta- thorax. Lateral margins of each thoracic and abdominal segment (except terminal segments 9 and 10 of abdomen) prolonged into a pair of unflattened, finger-like setigerous scoli, ten pairs in all. Each mesothoracic scolus (ScMs) fully as long as head capsule, inclined forward basally and reflexed backward at its mid-point. Metathoracic scoli (ScMt) two-thirds as long as mesothoracic ones, less sharply reflexed; remaining 8 pairs of abdominal scoli straight, shorter than thoracic ones, and becoming gradually smaller toward rear. Minute pair of vestigial scoli (Scvg) present behind and slightly ventral to primary pair on both meso- and metathorax. Meso- thoracic spiracles (SpMs) very large, borne dorso-laterally on cone- shaped sclerotized tubercles behind prothorax; all other spiracles smaller, ventro-laterally located, one pair for each of the first eight abdominal segments.
Chaetotaxy: Dense, double fringe of very long serrate setae pres- ent on lateral margins of head capsule and peripherally on all scoli. Single primary row of shorter, distally flared, serrate dolichasters (as in figure 8-a) closely set along entire anterior labral margin. Each ocular tubercle with still shorter, tightly packed dolichasterine setae over most of its distal surface, with two very large subequal setae projecting backward from the posterior outer margin. An- tennal tubercle bearing a group of three (very rarely, four) slender, smooth setae with apical stellate enlargements (SSt and figure 8-d) Figure 3. [opposite page] Ululodes mexicana. details of head capsule of mature third instar. A = anterior dorsal aspect, B = anterior ventral aspect. AT = antenna1 tubercle, Cd = maxillary cardo, ER = epistomal ridge, excv = lateral excavation, Gu = gular area, Gul = gular line, LmM = labral margin, MdCV = ventral mandibular condyle, OT = ocular tubercle, Plb = postlabium, Prlb = prelabial lobe, Pip = labial palp, SgR = subgenal ridge, SSt = stellate-tipped seta, St = maxillary stipes, TAP = anterior tentorial pit, TPP = posterior tentorial pit.



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Figure 4. Ululodes mexicana, first instar larva at hatching.



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Henry- Larval Owlflies
that contact antenna scape, flanked anteriorly by two (very rarely, three) stout serrate setae and posteriorly by an enlarged dolichaster; a few other, smaller dolichasters may also be present on surface of the tubercle. Dorsum of head and body more or less clothed with small to medium sized dolichasterine setae; ventral surfaces bear more profuse, smaller dolichasters that are shaped like goblets (figure 8-c). Thick mat of very fine, tangled threads also present over entire dorsum of larva, including dorsal surfaces of all setal fringes on head and scoli. Four of five pairs of stout, tooth-like digging setae present terminally on ninth abdominal segment. SPECIES DESCRIPTION: Ululodes mexicana (McLachlan), new larval association.
Measurements: Length of mature larva, 14.60-18.75 mm, mean length = 16.00 mm. Length of head capsule, 3.30-3.78 mm, mean = 3.54 mm; width of head capsule, 3.40-3.90 mm, mean = 3.60 mm. Chaetotaxy: Setae composing fringes on lateral margins of head capsule and edges of scoli showing tendency toward gradual distal thickening with truncate tips (figure 8-a); not lanceolate. Ocular dolichasters projecting well beyond edges of stemmata and easily visible from above. Dolichasters on dorsal surface of head abun- dant, fairly evenly distributed, and cavlate (figure 8-b-2); never peg like (figure 8-b-1) or confined to occipital lobes. Dolichasters on dorsal body surface of the flared and curved type (figure 8-a), rarely parallel sided or pointed.
Pigmentation: Head with prominent but diffuse oval to heart- shaped spot of dark pigmentation centered just behind (but encom- passing) anterior tentorial pits (TAP). Labral lobes, antenna1 tubercles, and tips of ocular tubercles also darkly pigmented. Oc- cipital lobes noticeably more pale than the rest of the head capsule. Prothoracic notum without obvious pattern of pigmentation. ONTOGENETIC VARIATION:
The first instar Ululodes larva (figure 4) differs considerably from the mature larva. The head capsule is more quadrate than trapezoidal. The antenna is more than twice the length of the ocular tubercle, bears 12 or 13 flagellomeres, and emerges from a poorly defined tubercle. The jaws are only slightly falcate, and the proximal tooth rather than the distal tooth is the smallest of the three. All setae are relatively longer and less numerous than in mature larvae: the central dorsal aspect of the head capsule in particular is nearly



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devoid of setae in all forms studied. A single stellate seta rather than three (or four) is found on each antennal tubercle, flanked by (usually) one large stout seta anteriorly and one posteriorly. Terminal digging teeth on abdominal segment nine are lacking. The second instar larva is intermediate between first and third instars with respect to most ontogenetically variable morphological features, Three stellate setae are borne by each antennal tubercle. The generic discussion applies equally well to the species U. mex- icana. It is considerably more difficult to distinguish among species in the first instar than in later instars, although the morphology of the long setae bordering the head and covering the body and scoli seems to separate first and second instar U. mexicana larvae from those of at least one undetermined species from Florida. Addition- ally, consistent differences in the pigmentation patterns of the dor- sum of the head capsule can be found in early instars. However, other setal patterns uniquely characterizing mature U. mexicana larvae are absent or unreliably present in younger individuals. LARVA OF ASCALOPTYNX FURCZGER (McLachlan) (Refer to figures 5-7)
GENERIC DESCRIPTION: Ascaloptynx Banks.
The following description is based upon examination of 67 third instar larvae reared from field-collected eggs that were morpho- logically matched with eggs obtained from females of Ascaloptynx furciger. A. furciger is the only species of the genus that has been sighted or collected from the vicinity of the egg collecting sites in the Chiricahua Mountains. Two additional specimens of an un- identified larva from Pima, Arizona that can be assigned with con- fidence to the genus on the basis of morphology were also available for comparison. In addition, the two figures published by Peterson (1953) are almost certainly of Ascaloptynx larvae, although the drawings are too schematic to contribute much morphological information.
Length: just prior to pupation, 16-22 mm, not including jaws. Head: quadrate, slightly wider than long, slightly broader pos- teriorly than anteriorly but basically parallel sided; strongly flat- tened dorso-ventrally but thicker behind than in front. Moderately