Ralph W. Howard

Cuticular hydrocarbons ofReticulitermes virginicus (Banks) and their role as potential species- and caste-recognition cues.

The cuticular hydrocarbon components of four castes ofReticulitermes virginicus (Banks) have been identified and quantitated. Components identified includen-alkanes; 2-, 3-, 11-, 13-, and 15-methyl-alkanes; 11,15-dimethylalkanes, (Z)-9-alkenes; (Z,Z)-7,9-dienes; and (E/Z)-6,9-dienes ranging in carbon number from C21 to C40. All caste forms ofR.virginicus contained the same components, but showed caste-specific proportions. Comparison of these hydrocarbons with those of the sympatric termiteR. flavipes (Kollar) suggest that cuticular hydrocarbons might serve as species- and caste-recognition cues. A bioassay was developed to test this species-recognition hypothesis, with the experimental results supporting the hypothesis.

Chemical Mimicry as an Integrating Mechanism: Cuticular Hydrocarbons of a Termitophile and Its Host

The staphylinid beetle Trichopsenius frosti Seevers has the same cuticular hydrocarbons as those of its host termite Reticulitermes flavipes (Kollar) and it biosynthesizes them. These cuticular hydrocarbons probably serve as the primary mechanism by which Trichopsenius frosti integrates itself into the termite colony.

Cuticular hydrocarbons of the eastern subterranean termite,Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae)

Major cuticular hydrocarbon components in several castes ofReticulitermes flavipes (Kollar) have been identified and quantitated. Types of hydrocarbons present includen-alkanes, 2-methylalkanes, 3-methylalkanes, 5-methylalkanes, an alkene, and an alkadiene, with a range in carbon numbers from C21 to C26, This is the first report on insect cuticular hydrocarbons in which both 2- and 3-methylalkanes are present, as well as the first report of an insect with a conjugated alkadiene.

Re-analysis of the cuticular methylalkanes of Solenopsis invicta and S. richteri

Gas chromatographic retention times and electron impact and chemical ionization mass spectrometry were used to identify two new series of dimethylalkanes in Solenopsis invicta Buen and Solenopsis richteri Forel. The first series consisted of internally branched dimethylalkanes with one methylene group between the branch points and were identified in an extract of cuticular lipids from S. invicta and S. richteri. The second new series consisted of 3,x-dimethylalkanes with odd carbon numbers, where x = 7, 9, or 11, and 4,x-dimethylalkanes with even numbers, where x = 8, 10, or 12. The mass spectrum published by Loket al. (1975), and which was tentatively identified as being that of 10,12-dimethyltricosane, is re-interpreted as being that of a mixture of 3,9- and 3,11-dimethyltricosanes. Internally branched monomethylalkanes, and 3- and 4-methylalkanes were found in the cuticular lipids of both species. 3,7,11-Trimethylalkanes were tentatively identified as being present in S. invicta. The n-alkanes and alkenes also were identified in S. richteri.

Venom chemistry of ants in the genusMonomorium

A comparative analysis of the venomous alkaloids produced by ant species in the subgenusMonomorium of the genusMonomorium has been undertaken. All species produce mixtures of unsymmetricaltrans-2,5-dialkylpyrrolidines, but the proportions of the constituents may vary considerably between species. All alkaloids contain both C6 and C9 side chains which are present as C9-saturated. C6-monounsaturated, and both C6-and C9-monounsaturated dialkylpyrrolidines. The structure of 2-(1-hex-5-enyl)-5-(1-non-8-enyl)pyrrolidine, a previously undescribed alkaloid, was proved by unambiguous synthesis after the location of the double bonds was established by the methoxymercuration-demercuration followed by mass spectrometry. The possible chemotaxonomic significance of the mixtures of venomous alkaloids produced by these species ofMonomorium is discussed.

Vitamin B12 levels in selected insects

Abstract Vitamin B 12 concentrations were determined by radioassay in the housefly, five species of termites, and 17 other phylogenetically diverse insect species. Vitamin B 12 was not detected in the housefly Musca domestica , which apparently cannot interconvert propionate and succinate. In contrast, the termite Zootermopsis angusticollis readily interconverts succinate and methylmalonate, and contains high amounts of vitamin B 12 (940 pg/mg dry tissue), as do four other species of termites. Experiments involving selective elimination of either gut tract protozoa or bacteria in Coptotermes formosanus indicate that intestinal bacteria are the major source of vitamin B 12 in this termite. The other insect species examined have undetectable to moderate amounts of vitamin B 12 .

Biosynthesis of the cuticular hydrocarbons of the termite Zootermopsis angusticollis (Hagen). Incorporation of propionate into dimethylalkanes

The biosynthesis of hydrocarbons was investigated in the termite Zootermopsis angusticollis. Labelled acetate and propionate were readily incorporated into the cuticular hydrocarbons of this insect, with the soldier and worker castes incorporating these substrates into hydrocarbon more efficiently than nymphs. Palmitate was incorporated into hydrocarbon by workers to about the same extent as acetate. Analysis of the radioactive products by radio-GLC showed that acetate was incorporated at appreciable levels into each of the major components of the hydrocarbon fraction. In contrast, palmitate preferentially labelled the η-alkanes and propionate preferentially labelled the methyl branched components. Of the [1-14C]-propionate that was incorporated into hydrocarbon by nymphs, 24.6 ± 4.5% of the radioactivity was recovered in 5-methylheneicosane and 54.9 ± 8.4% in 5,17-dimethylheneicosane. Similar data were obtained in the worker and soldier castes. These data suggest that the branching methyl groups of both the mono- and dimethylalkanes arise from the incorporation of propionate in place of acetate during chain elongation.

Mating Behavior of Cephalonomia tarsalis (Ashmead) (Hymenoptera: Bethylidae) and the Effect of Female Mating Frequency on Offspring Production

The courtship behavior of Cephalonomia tarsalis, a solitary semiectoparasitoid of Oryzaephilus surinamensis, was investigated in the laboratory. Courtship behavior includes a series of stereotypic movements. Males play the most active role, executing the majority of courtship action, and females respond with relatively limited observable behaviors. Males typically keep antennae still during encounters with females prior to mounting, which may be correlated with recognition of the females sexual status. After mounting, males display a series of movements on females, such as antennae touching females antennae, antennae or mouth touching females head or thorax, and walking around on female, which may serve to stimulate females towards increased receptivity. Females signal receptivity by assuming a stereotypical posture of remaining stationary, with head down, and antennae still in front of the body. The male then inserts his aedeagus and the pair copulates. After an average of 40.4 s of copulation, females signal the end of copulation by waving the antennae and moving away from the copulation site. Males continue copulating for a short time after females start moving but dismount soon thereafter. After dismounting, the two wasps move away from each other immediately, and they typically begin grooming. Neither males nor females exhibit mating preference based on mates mating status in both choice and no-choice tests. The male is polygynous and the mated female can mate multiple times within the first 3 days after starting oviposition. However, female mating frequency does not affect the production of female progeny.

Laboratory Evaluation of Within-Species, Between-Species, and Parthenogenetic Reproduction in Reticulitermes Flavipes and Reticulitermes Virginicus

Considerable interest currently exists regarding the reproductive strategies of social insects (Blum and Blum, 1979; Crozier, 1979). Among termites (Order Isoptera) colony foundation by alate pairs, fusion of existing colonies, splitting of existing colonies, and parthenogenesis have all been reported (Nutting, 1969). Little information is available regarding the relative importance of each of these strategies. The genus Reticulitermes (Rhinotermitidae) contains six Nearctic and twelve Palearctic species, three of which have been critically examined for reproductive modes. Pickens (1932) and Weesner (1956) studied colony foundation of R. hesperus Banks by male + female dealate pairs, as well as by parthenogenesis. Buchli (1950) studied similar strategies for R. lucifugus Rossi. Clement (1979) studied interspecific hybridizationof R. santonensis Feytaud and R. iucifugus. More limited studies on colony foundation by male + female dealate pairs of R.flavipes (Kollar) were conducted by Beard (1974). Field studies with R. flavipes (Howard and Haverty, 1980) suggest that an important reproductive strategy for this species is colony splitting with subsequent production of numerous (several hundred) neotenic reproductives. However, sizeable alate flights are also a prominent feature of the biology of Reticulitermes spp. and

Mass spectral determination of aldehydes, ketones, and carboxylic acids using 1,1-dimethylhydrazine

Analyses of nanogram to milligram quantities of aliphatic aldehydes, fatty acids, and unhindered aliphatic ketones such as those typically found in pheromonal blends have been effected by treating these mixtures with 1,1-dimethylhydrazine. The aldehydes and ketones formN,N-dimethylhydrazones, while the fatty acids form methyl esters. Structural elucidation of the reaction products was achieved using EI and CI gas chromatography-mass spectrometry.